PB165242 PG068 – PG106

5/22/2018 PB165242 PG068 PG106

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68

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Electromagnetism

Keelektromagnetan

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1. http://www.school-for-champions.com/science/electromagnetism.htm 2. http://micro.magnet.fsu.edu/electromag/java/faraday2/ 3. http://micro.magnet.fsu.edu/electromag/java/generator/ac.html 4. http://micro.magnet.fsu.edu/electromag/java/lenzlaw/index.html 5. http://micro.magnet.fsu.edu/electromag/java/transformer/index.html 6. http://www.lincoln.smmusd.org/science/7th%20Grade/physics_applets/phe/generator_e.htm

!"# %&&"''

To analyse the magnetic effect of a current-carrying conductor To analyse electromagnetic inductionTo understand the force on a current-carrying conductor To analyse transformers

in a magnetic field To understand the generation and transmission of electric

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Physics Form 5 Chapter 3 ElectromagnetisDate:

69

!"#$!%&!"# The pattern and direction of the magnetic field due to a curr

Corak dan arah bagi medan magnet yang disebabkan oleh arus Inquiry-Dis

Aim To study the pattern and direction of the magnetic field due to a current in a

I

straight wire

II circular coil

III solenoid

Apparatus I A rectangular coil of insulated copper wire, 4 compasses, low voltage d.c. power supply

connecting wires

!"#"$% ("#) "*+,- .,/,) 0%+1%* 2"1+"&"2,-3 ! 04*+,(3 2"0,$,& 0%,(, ,5-5 64$-,& 1"&.,7 .,&

+"&8,*2%

II A circular coil of insulated copper wire, 4 compasses, low voltage d.c. power supply

connecting wires

!"#"$% 2%$,- .,/,) 0%+1%* 2"1+"&"2,-3 !04*+,(3 2"0,$,& 0%,(, ,5-5 64$-,& 1"&.,7 .,& .,/,) +"&8,* III Solenoid made of copper wire, 4 compasses, low voltage d.c. power supply and conne

wires

94$"&4). 8, .)+"12%,- .,1)+,., .,/,) 0%+1%*3 ! 04*+,(3 2"0,$,& 0%,(, ,5-5 64$-,& 1"&.,7 .,&

+"&8,*2%

Material Iron filings

9"12%0 2"()

(I) Straight wire

!"#"$ &'(')

Procedure 1. Set up the apparatus as shown in the diagram.

9".),0,& 1,.,( ("+"1-) 8, .)-%&:%00,& .,$,* 1,:,75

Rectangularcoil of insulatedcopper wire

Gegelung segi empatdawai kuprumberpenebat

Iron filings

Serbuk besiPlastic plate

Plat plastik

d.c. powersupply

Bekalankuasa a.t.

2. Switch on the current.;).%+0,& ,1%(5

3. Tap the plastic plate slowly and observe the pattern formed by the iron filings.

41,0 8, .)2"&-%0 4$"7 ("12%0 2"() )-%5

! !"#$#!"!"#$%!$% & '()*+, -. /01(

2112)*(3 0) 4-)4()+104 10)*5

! %"$&'"#(#&'#"%'()$% & 46'0)31042

4-0' -. /01( 24+0)* 25 2 72*)(+ /

421160)* ('(4+104 4811()+

Learning Outcome

Draw the magnetic field pattern due to a current in a straight wire, coil andsolenoid.


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Physics Form 5 Chapter 3 Electromagnetism Date:

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4. Place four compasses around the wire and observe the direction

shown by the compasses.

?"-,00,& "*+,- 04*+,( .) ("0"$)$) .,/,) )-% .,& +"17,-)0,& ,1,7 8,

.)-%&:%00,& 4$"7 04*+,(=04*+,( )-%5

5. Sketch the pattern of the magnetic field and label its direction.

?,0,10,& >41,0 *".,& *,#&"- .,& $,2"$0,& ,1,7&8,5

6. Reverse the connections to the terminals of the d.c. power supply. Observe the patte

shown by the iron filings and the direction shown by the compasses.

94(,,& (,*2%,& 0"+,., -"1*)&,$ ,5-5 2"0,$,& 0%,(,5 @"17,-)0,& >41,0 8, .)-%&:%00,& 4$"7 ("12

2"() .,& ,1,7 8, .)-%&:%00,& 4$"7 04*+,(=04*+,(5

7. Sketch the pattern of the magnetic field and label its direction.

?,0,10,& >41,0 *".,& *,#&"- .,& $,2"$0,& ,1,7&8,5

8. Switch off the current.

A,-)0,& ,1%(5

(II) Circular coil

*+,+&'-, .'&"/

1. Set up the apparatus as shown in the diagram. 9".),0,& 1,.,( ("+"1-) .)-%&:%00,& .,$,* 1,:,75

Circular coil ofinsulated copperwire

Gegelung bulat

dawai kuprumberpenebat

d.c. powersupply

Bekalankuasa a.t.

2. Repeat steps 2 to 8 in (I). B$, $,,7=$,,7 "7)#, #.) CDE5

(III) Solenoid

01&+-1$2

1. Set up the apparatus as shown in the diagram.

9".),0,& 1,.,( ("+"1-) 8, .)-%&:%00,& .,$,* 1,:,75

d.c. powersupply

Bekalankuasa a.t.

Solenoid madeof copper wire

Solenoid yangdiperbuat daripadadawai kuprum

! &) &$&)*+",-.'&*#"#"*+,'-.!%"+$% &

+69( -. 72*)(+ 0) /,04, +,( 72*)(+0

!('3 05 91-384(3 :6 2 "-/ -. ('(4+104

4811()+


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2. Repeat steps 2 to 8 in (I).

B$, $,,7=$,,7 "7)#, #.) CDE5

(I) Straight wire

!"#"$ &'(')

1. The apparatus was set up as shown in the diagram.

2. The current was switched on.

3. The plastic plate was tapped slowly and the pattern formed by the iron filings was obse

4. Four compasses were placed around the wire. The directions shown by the comp

were observed.

5. The pattern and direction of the magnetic field were sketched.

6. The connections to the d.c. power supply were reversed. The pattern of the

filings and direction of the compasses were observed.

7. The pattern and direction of the magnetic field were sketched.

8. The current was switched off.

(II) Circular coil

*+,+&'-, .'&"/


2. Steps 2 to 8 in (I) were repeated.

(III) Solenoid

01&+-1$2


2. Steps 2 to 8 in (I) were repeated.

(I) Magnetic field due to current in a straight wire

3+2"- 4",-+/ 5"-, 2$)+.".6"- 1&+7 "(') 2"&"4 2"#"$ &'(')

Current into the paper Current out of the paper

F1%( *,(%0 0" .,$,* 0"1-,( F1%( 0"$%,1 .,1) 0"1-,(

Method

Observations


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(II) Magnetic field due to current in a circular coil

3+2"- 4",-+/ 5"-, 2$)+.".6"- 1&+7 "(') 2"&"4 ,+,+&'-, .'&"/

(III) Magnetic field due to current in a solenoid

3+2"- 4",-+/ 5"-, 2$)+.".6"- 1&+7 "(') 2"&"4 )1&+-1$2

Discussion 1. What is the advantage of using more turns of copper wire?

F+,0,7 0"$"2)7,& *"#%&,0,& $"2)7 2,&8,0 $)$)-,& .,/,) 0%+1%*G ;

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4. What is the factor that determines the direction of the magnetic field?

F+,0,7 H,0-41 8, *"&"&-%0,& ,1,7 *".,& *,#&"-G ;

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Current in short copper wire8(') 2"&"4 2"#"$ 6'9('4 9+-2+6

Motion of short copper wire*+("6"- 2"#"$ 6'9('4 9+-2+6

Current flows in one directionF1%( *",$)1 .,$,* (,-% ,1,7

Moves in one direction

Current flows in opposite directionF1%( *",$)1 .,$,* ,1,7 8, 2"1$,/,&,&

Moves in the opposite direction

Discussion 1. Is there a magnetic field in the region around the short copper wire before the current

switched on?

F.,0,7 -"1.,+,- (%,-% *".,& *,#&"- .) 0,/,(,& ("0"$)$) .,/,) 0%+1%* +"&."0 ("2"$%* ,1%( .)7).%+0,&G

;

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75

!"#$!%&!"! The turning effect on a current-carrying coil in a magnetic fi

Kesan putaran pada gegelung yang membawa arus dalam medan magInquiry-Disc

Aim To study the turning effect on a current-carrying coil placed in a magnetic field

Apparatus Low voltage d.c. power supply I"0,$,& 0%,(, ,5-5 64$-,& 1"&.,7

Materials Insulated copper wire (s.w.g. 26), wooden former, a thin iron rod to act as an axle, wo

block as the base, a pair of magnadur magnets with U-shaped steel yoke, two split pins

cellophane tape

J,/,) 0%+1%* 2"1+"&"2,- C(5/5#5 "%E3 1,, 0,8%3 14. 2"() &)+)( ("2,#,) #,&.,13 24,7 0,8% ("2,#,)

("+,(, *,#&"- *,#&,.%1 .",& ."&) 0"$%$) 2"12"&-%0=B3 .%, :,1%* +"&)-) -"12"$,7 .,& +)-, ("$4H,&


9".),0,& 1,.,( ("+"1-) 8, .)-%&:%00,& .,$,* 1,:,75

d.c. powersupply

Bekalankuasa a.t.

Magnadur magnet

Magnet magnadur

Wooden forme

Rangka kayu

Iron axle

Gandar besi

Wooden base

Tapak kayu

2. Switch on the current. Observe what happens to the coil of wire wound round the wo

former. [If it does not move, give it a slow push.]

;).%+0,& ,1%(5 @"17,-)0,& ,+, 8, 2"1$,0% +,., #"#"$% .,/,) 8, .)$)$)- 4$"7 1,, 0,8%5 LM)0, #"#

.,/,) )-% -).,0 2"1#"1,03 2"1)0,& (,-% -4$,0,& +"1$,7,&5N

3. Reverse the connections to the power supply. Repeat step 2.

94(,,& (,*2%,& 0"+,., 2"0,$,& 0%,(,5 B$, $,,7 O5

Method 1. The apparatus was set up as shown in the diagram.

2. The current was switched on. The motion of the coil was observed.

3. The connections to the power supply were reversed. Step 2 was repeated.

Learning Outcome

Describe how a current-carrying coil in a magnetic field experiences a turningforce.


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Switch at power supply0'$) 9"2" .+6"&"- 6'")"

Current8(')

Coil*+,+&'-,

OFFPJDAFQD

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!"#$!%&!"% The factors that affect the speed of rotation of an electric mo

Faktor-faktor yang mempengaruhi laju putaran sebuah motor elektrikInquiry-Disc

Aim To investigate the factors that affect the speed of rotation of an electric motor

Apparatus Low voltage d.c. power supply

I"0,$,& 0%,(, ,5-5 64$-,& 1"&.,7

Materials Insulated copper wire (s.w.g. 26), wooden former, a thin iron rod to act as an axle, wo

block as the base, two pairs of magnadur magnets with U-shaped steel yoke, two split pin

cellophane tape

J,/,) 0%+1%* 2"1+"&"2,- C(5/5#5 "%E3 1,, 0,8%3 14. 2"() &)+)( ("2,#,) #,&.,13 24,7 0,8% ("2,#,) -,+,

+,(, *,#&"- *,#&,.%1 .",& ."&) 0"$%$) 2"12"&-%0=B3 .%, :,1%* +"&)-) -"12"$,7 .,& +)-, ("$4H,&

Procedure 1. Set up the apparatus as shown in the diagram of Activity 3.3. Use a coil with 40 turns r

the wooden former.

9".),0,& 1,.,( ("+"1-) 8, .)-%&:%00,& .,$,* 1,:,7 F0-)6)-) T5T5 !%&,0,& #"#"$% .",& !$

*""$)$)) 1,, 0,8% )-%5

2. Set the voltage of the d.c. power supply to 1 V. Switch on the current and observe the s

of rotation of the motor. Q"-,+0,& 64$-,& 2,#) 2"0,$,& 0%,(, ,5-5 +,., U &5 ;).%+0,& ,1%( .,& +"17,-)0,& $,:% +%-,1,& *4-415

3. Repeat step 2 with a voltage of 2 V.

B$, $,,7 O .",& 64$-,& "&5

4. Set the voltage of the d.c. power supply back to 1 V.

Q"-,+0,& 64$-,& 2"0,$,& 0%,(, ,5-5 +,., '&("*%$,5

5. Add another pair of magnadur magnets to the U-shaped steel yoke, as

shown in the diagram of Activity 3.3. Switch on the current and observe

the speed of rotation of the motor.

Q,*2,7 ("+,(, $,#) *,#&"- *,#&,.%1 0"+,., ."&) 0"$%$) 2"12"&-%0=B ("+"1-) 8,

.)-%&:%00,& .,$,* 1,:,7 F0-6)-) T5T5 ;).%+0,& ,1%( .,& +"17,-)0,& $,:% +%-,1,& *4-415

6. Remove one pair of the magnadur magnets. Replace the coil of the motor with anotherthat has 80 turns of wire. Switch on the current and observe the speed of rotation o

motor.

F$)70,& ("+,(, *,#&"- *,#&,.%15 !,&-)0,& #"#"$% *4-41 .",& #"#"$% $,)& 8, *"*+

#$$)$)-,& .,/,)5 ;).%+0,& ,1%( .,& +"17,-)0,& $,:% +%-,1,& *4-415

Method 1. The apparatus was set up as shown in the diagram of Activity 3.3. The coil with 40

round the wooden former was used.

2. The voltage of the d.c. power supply was set to 1 V. The current was switched on and

speed of rotation of the motor was observed.

3. Step 2 was repeated with a voltage of 2 V.

4. The voltage of the d.c. power supply was set back to 1 V.

5. Another pair of magnadur magnets were added to the U-shaped steel yoke as shown in

diagram. The current was switched on and the speed of rotation of the motor was obse

Two pairs

magnadur m

Dua pasang m

magnad

Learning Outcome

State factors that affect the speed of rotation of an electric motor.


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78

6. One pair of the magnadur magnets were removed. The coil was replaced with another c

of 80 turns of wire. The current was switched on and the speed of rotation of the mot

was observed.

d.c. power

supply:+6"&"- 6'")" ";/;

Magnadur

magnets3",-+/ 4",-"2'(

Number of turns of

coil:$&"-,"- &$&$/"- ,+,+&'-,

Rotation of coil

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4. Describe the change in the speed of rotation of the motor when the strength of the mag

field increases.

;%1,)0,& +"1%2,7,& $,:% +%-,1,& *4-41 ,+,2)$, 0"0%,-,& *".,& *,#&"- 2"1-,*2,75

@('2+0)* = /"%!4$1$%

The speed of rotation increases when the strength of the magnetic field increases.

5. Describe the change in the speed of rotation of the motor when the number of turns o

coil increases.

;%1,)0,& +"1%2,7,& $,:% +%-,1,& *4-41 ,+,2)$, 2)$,,& $)$)-,& #"#"$% 2"1-,*2,75

@('2+0)* = /"%!4$1$%

The speed of rotation increases when the number of turns of the coil increases.

6. What are the factors affecting the speed of rotation of a motor?

F+,0,7 H,0-41=H,0-41 8, *"*+",1%7) $,:% +%-,1,& *4-41G &++10:8+0)* = /"

Current in the coil, strength of the magnetic field and the number of turns of the coil

Conclusion The speed of rotation of an electric motor increases when the current in the coil, the streng

the magnetic field or the number of turns of the coil increases.

Precaution The current should be switched on long enough for the observation to be recorded. After

the current is switched off to avoid overheating the wires of the coil.

!"#$!%&!"& Electromagnetic induction in a conductor

Aruhan elektromagnet dalam suatu konduktor Inquiry-Dis

Aim To observe electromagnetic induction in a straight wire and solenoid

(I) Electromagnetic induction in a straight wire

8('7"- +&+6/(14",-+/ 2"&"4 2"#"$ &'(')

Apparatus Magnadur magnets, connecting wires with crocodile clips and

sensitive centre-zero galvanometer

A,#&"- *,#&,.%13 .,/,) +"&8,*2% .",& 0$)+ 2%,8, .,& #,$6,&4*"-"1

()H,1=-",7 8, +"0,

Material Copper rod with bare ends

V4. 0%+1%* .",& 7%:% -,&+, +"&"2,-

! /$&)*+",-.'&*#) #'(1)*#"' #.,$"#"*+,'-.!%"+$% & 91-4(55 -.

91-3840)* 2) (C7C.C 0) 2 4-)384+

/,() +,( 4-)384+-1 05 0) 2 4,2)

72*)(+04 !('3

! 2'(1)&( )1++&'* #.,$& +",.,$4$%

D811()+ +,2+ 05 91-384(3 0) 2

4-)384+-1 +,2+ 05 0) 2 4,2)*0)*

72*)(+04 !('3

Learning Outcome

Describe electromagnetic induction.


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9".),0,& 1,.,( ("+"1-) 8, .)-%&:%00,& .,$,* 1,:,75

G

Galvanometer

Galvanometer

Connecting wireswith crocodile clips

Wayar penyambungdengan klip buaya

Copper rod withbare ends

Rod kuprum denganhujung tanpa penebat

Magnadurmagnet

Magnetmagnadur

15

4

26

3

2. Hold the copper rod stationary between the poles of the magnet. Observe the reading of tgalvanometer pointer.

@"#, 14. 0%+1%* )-% (%+,8, 14. )-% +"#%& .) ,&-,1, 0%-%2=0%-%2 *,#&"-5 @"17,-)0,& 2,>,,& +"&%&:

#,$6,&4*"-"15

3. Move the rod quickly in Direction 1 as shown in the diagram. Observe the deflection of th

galvanometer pointer.

!"1,00,& 14. )-% .",& >"+,- .,$,* F1,7 U ("+"1-) 8, .)-%&:%00,& .,$,* 1,:,75 @"17,-)0,& +"(4

+"&%&:%0 #,$6,&4*"-"15

4. Repeat steps 2 and 3 for the other directions 2, 3, 4, 5 and 6.

B$, $,,7=$,,7 ".,& (2,#) ,1,7=,1,7 $,)& ") () !) +.,& %5


2. The copper rod was held stationary between the poles of the magnet. The reading of t

galvanometer pointer was observed.

3. The rod was moved quickly in Direction 1 as shown in the diagram. The deflection of t

galvanometer pointer was observed.

4. Steps 2 and 3 were repeated for directions 2, 3, 4, 5 and 6.

Motion of rod*+("6"- (12

Deflection of galvanometer pointer"-14+/+(

Rod at restV4. .,$,* 0",.,,& 1"7,-

No deflection

Direction 1F1,7 U

Deflected in one direction

Observations


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Motion of rod*+("6"- (12

Deflection of galvanometer pointer"-14+/+(

Direction 2F1,7 O

Deflected in the opposite direction

Direction 3

F1,7 T No deflection

Direction 4F1,7 W

No deflection

Direction 5F1,7 X

No deflection

Direction 6F1,7 Y

No deflection

Discussion 1. Describe the magnetic field lines between the poles of the magnet.

;%1,)0,& #,1)(=#,1)( *".,& *,#&"- .) ,&-,1, 0%-%2=0%-%2 *,#&"-5 B()(12+0)* 03(25 = /"%5

The magnetic field lines are horizontal lines from the North pole to the South pole.

2. What is detected by the galvanometer when its pointer shows a deflection?

F+,0,7 8, .)0"(,& ,+,2)$, +"&%&:%0 #,$6,&4*"-"1 *"&%&:%00,& (%,-% +"(4,&G

&)2'650)* = /"%

Electric current

3. What are the directions of motion that produce a current in the copper rod?

F+,0,7 ,1,7 #"1,0,& 8, *",()$0,& ,1%( .,$,* 14. 0%+1%* )-%G &++10:8+0)* = /"

Directions 1 and 2

4. Relate the motion of the copper rod that produces a current in it to the direction o

magnetic field lines.

;%2%,)-0,& #"1,0,& 14. 0%+1%* 8, *",()$0,& ,1%( .",& ,1,7 #,1)( *".,& *,#&"-5

@('2+0)* = /"%!4$1$%

A current flows in the copper rod when its motion cuts across the magnetic field lines

(II) Electromagnetic induction in a solenoid

8('7"- +&+6/(14",-+/ 2"&"4 )'"/' )1&+-1$2

Apparatus Bar magnet, connecting wires and sensitive centre-zero galvanometer

A,#&"- 2,-, .,/,) +"&8,*2% .,& #,$6,&4*"-"1 ()H,1=-",7 8, +"0,

Material Solenoid with at least 600 turns

94$"&4). .",& ("0%1,=0%1,&8, %$$$)$)-,&


9".),0,& 1,.,( ("+"1-) 8, .)-%&:%00,& .,$,* 1,:,75


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82

2. Push the bar magnet into the solenoid. Observe the

deflection of the galvanometer pointer.

Q4$,0 *,#&"- 2,-, 0" .,$,* (4$"&4).5 @"17,-)0,& +"(4,& +"&%&:%0

#,$6,&4*"-"1 )-%5

3. Hold the bar magnet stationary in the solenoid. Note the

reading of the galvanometer.

@"#, *,#&"- 2,-, (%+,8, *,#&"- )-% +"#%& .,$,* (4$"&4).5@"17,-)0,& 2,>,,& #,$6,&4*"-"1 )-%5

4. Now, pull the bar magnet out of the solenoid. Observe the

deflection of the galvanometer.

9"0,1, -,1)0 *,#&"- 2,-, )-% 0"$%,1 .,1) (4$"&4).5 @"17,-)0,&

+"(4,& +"&%&:%0 #,$6,&4*"-"1 )-%5

5. Hold the bar magnet stationary. Push the solenoid towards

the bar magnet. Observe the deflection of the galvanometer pointer.

@"#, *,#&"- 2,-, (%+,8, *,#&"- )-% .,$,* 0",.,,& +"#%&5 Q4$,0 (4$"&4). )-% *"&%:%) *,#&"- 2,-,

@"17,-)0,& +"(4,& +"&%&:%0 #,$6,&4*"-"1 )-%5

6. Pull the solenoid away from the bar magnet. Observe the deflection of the galvanomet

pointer.

Q,1)0 (4$"&4). )-% *"&:,%7) *,#&"- 2,-, @"17,-)0,& +"(4,& +"&%&:%0 #,$6,&4*"-"1 )-%5


2. The bar magnet was pushed into the solenoid. The deflection of the galvanometer pointer w

observed.

3. The bar magnet was held stationary in the solenoid. The reading of the galvanometer w

recorded.

4. The bar magnet was pulled out of the solenoid. The deflection of the galvanometer point

was observed.

5. The bar magnet was held stationary. The solenoid was pushed towards the bar magn

The deflection of the galvanometer pointer was observed.

6. The solenoid was pulled away from the bar magnet. The deflection of the galvanomet

pointer was observed.

Bar magnet3",-+/ ."/"-,

Solenoid01&+-1$2

Galvanometer*"&>"-14+/+(

Pushed into the

solenoidJ)-4$,0 0" .,$,* (4$"&4).

Stationary@"#%&

Shows a deflection

Stationary@"#%&

Stationary@"#%&

No deflection

Observations

G

Galvanomete

Galvanomete

Connecting wire

Dawaipenyambung

Solenoid

Solenoid

Bar magnet

Magnet batang


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83

Bar magnet3",-+/ ."/"-,

Solenoid01&+-1$2

Galvanometer*"&>"-14+/+(

Pulled out of the

solenoidJ)-,1)0 0"$%,1 .,1) (4$"&4).

Stationary@"#%&

Deflection in the opposite direction

Stationary@"#%&

Pushed towards barmagnetJ)-4$,0 *"&%:%) *,#&"-

2,-,

Shows a deflection

Stationary@"#%&

Pulled away from bar

magnetJ)-,1)0 *"&:,%7) *,#&"-

2,-,

Deflection in the opposite direction

Discussion 1. What happens to the deflection of galvanometer pointer when the magnet and sole

were coming closer to each other?

F+,0,7 8, 2"1$,0% +,., +"(4,& +"&%&:%0 #,$6,&4*"-"1 ,+,2)$, *,#&"- .,& (4$"&4). 2"1#"1,0 *"&

(,-% (,*, $,)&G >2?0)* 0).(1()4(5 = /"-1$.+

The galvanometer pointer shows a deflection.

2. What happens to the deflection of galvanometer pointer when the magnet and sole

were moving further away from each other?

F+,0,7 8, 2"1$,0% +,., +"(4,& +"&%&:%0 #,$6,&4*"-"1 ,+,2)$, *,#&"- .,& (4$"&4). 2"1#"1,0 *"

(,-% (,*, $,)&G >2?0)* 0).(1()4(5 = /"-1$.+

The galvanometer pointer shows a deflection in the opposite direction.

3. Write a general statement on how a current can be induced in a solenoid usi

magnet. Q%$)(0,& )"/' +"1&8,-,,& %*%* 2,#,)*,&, ,1%( .,+,- .),1%70,& .,$,* (,-% (4$"&4). .",& *"#%

(,-% *,#&"-5 >2?0)* *()(12'052+0-)5 = /"%!

A current is induced in a solenoid when there is relative motion between the solenoid a

magnet.

Conclusion Current is induced in a conductor when there is motion that causes the cutting of magnetic

Precaution

Ensure that the connections at the ends of the connecting wires are tight and have

electrical contact.


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!"#$!%&!"' The factors that affect the magnitude of the induced current

Faktor-faktor yang mempengaruhi magnitud arus teraruh Inquiry-Discov

Aim To study the factors that affect the magnitude of the induced current

Apparatus

Sensitive centre-zero galvanometer !,$6,&4*"-"1 ()H,1=-",7 8, +"0,

Materials Two solenoids with 600 and 1200 turns respectively, two bar magnets, connecting wires an

rubber bands

J%, (4$"&4). .",& %$$.,& '"$$$)$)-,& *,()=*,() .%, *,#&"- 2,-, .,/,) +"&8,*2% .,& #"$, #"


9".),0,& 1,.,( ("+"1-) 8, .)-%&:%00,& .,$,* 1,:,75

Galvanometer

Galvanometer

Connecting wire

Dawaipenyambung

Solenoid

Solenoid

Bar magnet

Magnet

batang

G

2. Push a bar magnet very slowly into the solenoid of 600 turns. Record the maximum readi

of the galvanometer.

Q4$,0 *,#&"- 2,-, .",& (,,- +"1$,7,& 0" .,$,* (4$"&4). YZZ $)$)-,&5 V"04.0,& 2,>,,& *,0()*%* 2

#,$6,&4*"-"1 )-%5

3. Push the bar magnet quickly into the solenoid of 600 turns. Record the maximum readin

of the galvanometer.

Q4$,0 *,#&"- 2,-, .",& >"+,- 0" .,$,* (4$"&4). %$$$)$)-,&5 V"04.0,& 2,>,,& *,0()*%* 2,#) #,$6,&4*"

)-%5

4. Push the bar magnet very slowly into the solenoid of 1200 turns. Record the maximu

reading of the galvanometer.

Q4$,0 *,#&"- 2,-, .",& (,,- +"1$,7,& 0" .,$,* (4$"&4). '"$$$)$)-,&5 V"04.0,& 2,>,,& *,0()*%* 2

#,$6,&4*"-"1 )-%5

5. Use the rubber bands to tie the two bar magnets together with like poles side by side.

!%&,0,& #"$, #"-,7 %&-%0 *")0,- .%, *,#&"- 2,-, 2"1(,*, .",& 0%-%2=0%-%2 8, (,

2"1("2"$,7,&5

6. Push the two magnets very slowly into the solenoid of 600 turns. Record the maximureading of the galvanometer.

Q4$,0 .%, *,#&"- )-% .",& (,,- +"1$,7,& 0" .,$,* (4$"&4). %$$$)$)-,&5 V"04.0,& 2,>,,& *,0()*%* 2

#,$6,&4*"-"1 )-%5

Learning Outcome

Explain factors that affect the magnitude of the induced current.


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2. A bar magnet was pushed very slowly into the solenoid of 600 turns. The maximum rea

of the galvanometer was recorded.

3. The bar magnet was pushed quickly into the solenoid of 600 turns. The maximum readi

the galvanometer was recorded.

4. The bar magnet was pushed very slowly into the solenoid of 1200 turns. The maxim

reading of the galvanometer was recorded.

5. Rubber bands were used to tie two bar magnets together with like poles side by side.

6. The two magnets were pushed very slowly into the solenoid of 600 turns. The maxim

reading of the galvanometer was recorded.

Number ofbar magnets

:$&"-,"- 4",-+/

."/"-,

Speed of

magnet?+&"='"- 4",-+/

Number

of turns of

solenoid:$&"-,"- &$&$/"-

)1&+-1$2

Maximum reading of galvanomete

:"@""- 4"6)$4'4 ,"&>"-14+/+(

First

attemptA'.""- 9+(/"4"

Second

attemptA'.""- 6+2'"

Averag

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86

(c) strength of the magnetic field?

0"0%,-,& *".,& *,#&"-G

The magnitude of the induced current increases when the strength of the magnetic fie

increases.

2. What are the factors that affect the magnitude of the induced current?

F+,0,7 H,0-41=H,0-41 8, *"*+",1%7) *,#&)-%. ,1%( -"1,1%7G &++10:8+0)* = /"%0(,

The speed of the relative motion of the magnet and the solenoid, the number of turns of t

solenoid and the strength of the magnetic field

Conclusion The magnitude of the induced current in a solenoid increases when the speed of the magnet, t

number of turns of the solenoid or the strength of the magnetic field increases.

Precaution Ensure that the connections at the ends of the connecting wires are tight and have go

electrical contact.

!"#$!%&!"( Direct current and alternating current

Arus terus dan arus ulang-alik Inquiry-Discov

Aim To compare the output generated by a direct current source and an alternating current sourc

Apparatus Battery holder with two dry cells, alternating current power supply, cathode ray oscillosco

(CRO), plug key switch and connecting wires

@"*"#, 2,-"1) .",& .%, ("$ 0"1) 2"0,$,& 0%,(, ,1%( %$,=,$)03 4()$4(04+ ()&,1 0,-4. C[9

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87

Battery holder withtwo dry cells

Pemegang bateridengan dua sel kering

CRO

OSK

Connecting wires

Dawai

penyambung

Bulb holder

Pemegang mentol

2.5 V bulbMentol 2.5 V

a.c. power supply

Bekalan kuasa a.u.

CRO

OSK

Connecting wires

Dawaipenyambung

Bulb holder

Pemegang mentol

2.5 V bulbMentol 2.5 V

3. Observe and compare the traces formed by the output from the battery and the altern

current supply.

@"17,-)0,& .,& 2,&.),& (%1)7,& 8, .)2"&-%0 4$"7 4%-+%- .,1)+,., 2,-"1) .,& 2"0,$,& ,1%( %$,=,$

4. Sketch the trace displayed on the screen of the oscilloscopes.

?,0,10,& (%1)7,& 8, .)+,+,10,& +,., (01)& 4()$4(04+5

Method 1. The two circuits were set up as shown in the diagram.

2. The cathode ray oscilloscope was adjusted to obtain a clear trace on the screen.

3. The traces formed by the output from the battery and the alternating current supply

observed and compared.

4. The trace displayed on the screen of the oscilloscopes was sketched.

Output from d.c. battery Output from a.c. supply

[%-+%- .,1)+,., 2,-"1) ,5-5 [%-+%- .,1)+,., 2"0,$,& ,5%5

Discussion 1. What type of current is supplied by two dry cells?

F+,0,7 :"&)( ,1%( 8, .)2"0,$0,& 4$"7 .%, ("$ 0"1)G &++10:8+0)* = /"

Direct current

Observations


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88

2. Are both the bulbs lighted up? Hence, make an inference on direct current and alternati

current.

F.,0,7 0".%,=.%, *"&-4$ )-% *"&8,$,G 9"-"1%(&8,3 &8,-,0,& )"/')&H"1"&( -"&-, ,1%( -"1%( .,& ,1%( %$,&

,$)05 >2?0)* 0).(1()4(5 = /"-1$.+ (%3"

Both bulbs are lighted up. Direct current and alternating current can flow through the bul

3. Based on your observations of the bulbs and the traces on the oscilloscopes, state

I"1.,(,10,& +"*"17,-),& ,&., 2,#) .%, *"&-4$ )-% .,& (%1)7,& +,., 4()$4(04+3 &8,-,0,&

(a) onesimilarity

)"/'+"1(,*,,&

(b) twodifferences

2'"+"12"\,,&

between the output generated by a direct current source and an alternating curre

source.

,&-,1, 4%-+%- 8, .):,&,0,& 4$"7 2"0,$,& ,1%( -"1%( .,& 2"0,$,& ,1%( %$,=,$)05

D-79210)* 2)3 4-)+125+0)* = /"-1.%)(%!*.% ).% -"-1"6.

(a) Both the direct current and alternating current produce heating effect in a wire.

(b) The direct current flows in one direction only. The direction of the alternating curre

changes with time. The magnitude of the direct current remains constant. T

magnitude of the alternating current changes between zero and a maximum value.

Conclusion A direct current flows in one direction only but the direction of an alternating current chang

with time.

Precaution The voltage supplied to the bulbs must not exceed the voltage rating labelled on the bulbs.

!"#$!%&!") A simple transformer

Transformer ringkas Inquiry-Discov

(I) Operating principle of a transformer

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89

Material Connecting wires

J,/,) +"&8,*2%


[The circuit is connected to the d.c. output of the power supply. The primary c

the coil connected to the power supply; the secondary coil is the coil connected to

galvanometer.] 9".),0,& 1,.,( ("+"1-) 8, .)-%&:%00,& .,$,* 1,:,75 L?)-,1 .)(,*2%,& 0"+,., 4%-+%- ,5-5 2"0,$,& 0%,(,5 !"#"$% +1)*"1 ),$,7 #"#"$% 8, .)(,*2%

0"+,., 2"0,$,& 0%,(,_ #"#"$% ("0%&."1 ),$,7 #"#"$% 8, .)(,*2%,& 0"+,., #,$6,&4*"-"15N

AC/DC L.T. POWERSUPPLY1 0Amp

G

Power supply

Bekalan kuasa

Switch

Suis

Galvanometer

Galvanometer

C-shapediron core

Teras besiberbentuk-C

Coppercoils

Gegelungkuprum

Rheostat

Reostat

! 3+-'45"+,&+#+,.%&3',-",$% & 3(

+,2+ 42) 0)41(25( -1 3(41(25( +,

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90

Current in the primary coil8(') 2"&"4 ,+,+&'-, 9($4+(

Galvanometer pointer

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Conclusion A current is induced in the secondary coil when the current in the primary coil is chan

When the current in the primary coil increases, the induced current in the secondary coil fl

in one direction. When the current in the primary coil decreases, the induced current in

secondary coil flows in the opposite direction.

Precaution The rheostat was used to limit the current in the primary circuit.

(II) Step-up transformer and step-down transformer

C("-)B1(4+( $-="6 -"$6 2"- /("-)B1(4+( $-="6 /'('-

Aim To understand a step-up transformer and a step-down transformer

Apparatus Two C-shaped iron cores with clip, low voltage a.c. power supply, two 2.5 V 0.3 A bulbs

holders, two 6.2 V 0.3 A bulbs with holders and voltmeter

J%, -"1,( 2"() 2"12"&-%0=] .",& 0$)+3 2"0,$,& 0%,(, ,5%5 64$-,& 1"&.,73 .%, *"&-4$ ",+&$,(-.",& +"*"

.%, *"&-4$ %,"& $,(-.",& +"*"#, .,& 64$-*"-"1

Materials 120 turns copper coil, 400 turns copper coil and connecting wires

!"#"$% 0%+1%* '"$$)$)-,&3 #"#"$% 0%+1%* WZZ $)$)-,& .,& .,/,) +"&8,*2%

Procedure (a) Step-up transformer

C("-)B1(4+( $-="6 -"$6

1. Set up the apparatus as shown in the diagram, with the 120 turns copper coil a

primary coil and the 400 turns copper coil as the secondary coil. [The primary coil is th

connected to the a.c. output of the power supply.]

9".),0,& 1,.,( ("+"1-) 8, .)-%&:%00,& .,$,* 1,:,73 .",& #"#"$% 0%+1%* UOZ $)$)-,& ("2,#,) #"#+1)*"1 ,&. #"#"$% 0%+1%* !$$ $)$)-,& ("2,#,) #"#"$% ("0%&."15 L!"#"$% +1)*"1 ),$,7 #"#"$%

.)(,*2%,& 0"+,., 4%-+%- ,5%5 2"0,$,& 0%,(,5N

AC/DC L.T.POWER SUPPLY 10Amp

Voltmeter

Voltmeter

Bulb with holder

Mentol denganpemegang

Voltmeter

Voltmeter

a.c. power supply

Bekalan kuasa a.u.

V

V

Bulb with holderMentol dengan

pemegang

Copper coil

Gegelungkuprum

C-shaped iron coreTeras besi berbentuk-C

2. Screw in the 6.2 V 0.3 A bulbs into the respective holders.

@,(,,& (01% *"&-4$=*"&-4$ %,"&$,(-*,()=*,() 0" .,$,* +"*"#,&8,5

Learning Outcome

Compare and contrast a step-up and a step-down transformer.


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92

3. Set the voltage of the power supply to 2 V a.c.

Q"-,+0,& 64$-,& 2,#) 2"0,$,& 0%,(, +,., "& ,5%5

4. Switch on the a.c. power supply. Compare the brightness of the bulbs.

;).%+0,& 2"0,$,& 0%,(, ,5%5 I,&.),& 0">"1,7,& *"&-4$=*"&-4$ )-%5

(b) Step-down transformer

C("-)B1(4+( $-="6 /'('-

5. Change the set-up of the apparatus so that the 400 turns copper coil becomes the prima

coil and the 120 turns coil becomes the secondary coil.

Q%0,1 (%(%&,& 1,.,( (%+,8, #"#"$% !$$ $)$)-,& *"&:,.) #"#"$% +1)*"1 .,& #"#"$% '"$ $)$)-,& *"&:

#"#"$% ("0%&."15

6. Replace the bulbs with 2.5 V 0.3 A bulbs.

!,&-) *"&-4$=*"&-4$ )-% .",& *"&-4$ ",+&$,(-5

7. Switch on the a.c. power supply. Compare the brightness of the bulbs.

;).%+0,& 2"0,$,& 0%,(, ,5%5 I,&.),& 0">"1,7,& *"&-4$=*"&-4$ )-%5

Method 1. The apparatus was set up as shown in the diagram, with the 120 turns copper coil as t

primary coil and the 400 turns copper coil as the secondary coil.

2. The 6.2 V 0.3 A bulbs were screwed into the respective holders.

3. The power supply was set to 2 V a.c.

4. The power supply was switched on. The brightness of the bulbs was compared.

5. The set-up of the apparatus was changed so that the 400 turns copper coil became t

primary coil and the 120 turns copper coil became the secondary coil.

6. The bulbs were replaced with 2.5 V 0.3 A bulbs.

7. The power supply was switched on. The brightness of the bulbs was compared.

(a) Step-up transformer

C("-)B1(4+( $-="6 -"$6

Primary circuitD$/"( 9($4+(

Secondary circuitD$/"( )+6'-2+(

Number of turns:$&"-,"- &$&$/"-

120 400

Brightness of bulb?+@+("7"- 4+-/1&

Dim Bright

Voltmeter reading:"@""- >1&/4+/+(

2.0 V 6.5 V

Observations


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93

(b) Step-down transformer

C("-)B1(4+( $-="6 /'('-

Primary circuitD$/"( 9($4+(

Secondary circuitD$/"( )+6'-2+(

Number of turns

:$&"-,"- &$&$/"-400 120

Brightness of bulb?+@+("7"- 4+-/1&

Bright Dim

Voltmeter reading:"@""- >1&/4+/+(

2.0 V 0.6 V

Discussion 1. What is the relationship between the brightness of the bulb and the voltage acros

bulb?

F+,0,7 7%2%,& ,&-,1, 0">"1,7,& *"&-4$ .",& 64$-,& *"1"&-,() *"&-4$ )-%G @('2+0)* = /"%!4$1$%

The brightness of the bulb is proportional to the voltage across the bulb.

2. State the condition for a transformer to step up an input voltage.

K8,-,0,& (8,1,- 2,#) -1,&(H41*"1 %&-%0 *"&,)00,& 64$-,& )&+%-5 >2?0)* 0).(1()4(5 = /"-1$.+

The number of turns in the secondary coil is more than the number of turns in the prim

coil.

3. State the condition for a transformer to step down an input voltage.

K8,-,0,& (8,1,- 2,#) -1,&(H41*"1 %&-%0 *"&%1%&0,& 64$-,& )&+%-5 >2?0)* 0).(1()4(5 = /"-1$.+

The number of turns in the secondary coil is less than the number of turns in the prim

coil.

Conclusion A voltage is induced in the secondary coil when the current in the primary coil is changin higher voltage is induced in the secondary coil when the secondary coil has more turns tha

primary coil.

Precautions 1. Ensure that the connections at the ends of the connecting wires are tight and have

electrical contact.

2. The C-shaped soft iron cores are clipped tightly to reduce leakage of magnetic flux.


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!"#$!%&!"* Relationship between the number of turns of the primary coi

and the secondary coil, voltage of primary coil and voltage osecondary coilHubungan antara bilangan lilitan gegelung primer dan gegelung sekundedengan voltan gegelung primer dan voltan gegelung sekunder Inquiry-Discove

To show the relationshipVP

VS

=NP

NS

Apparatus Two C-shaped iron cores, 0 12 V a.c. power supply and two a.c. voltmeters (0 10 V)

J%, -"1,( 2"() 2"12"&-%0=]3 2"0,$,& 0%,(, ,5%5 $ . '"&.,& .%, 64$-*"-"1 ,5%5 /$ . '$&0Materials Copper coils with 300, 600 and 900 turns respectively and connecting wires

!"#"$% 0%+1%* .",& ($$3 %$$.,& 1$$$)$)-,& *,()=*,() .,& .,/,) +"&8,*2%

Procedure 1. Set up the apparatus as shown in the diagram. Use

the 300 turns copper coil as the primary coil and the

600 turns coil as the secondary coil. 9".),0,& 1,.,( ("+"1-) 8, .)-%&:%00,& .,$,* 1,:,75

!%&,0,& #"#"$% 0%+1%* ($$ $)$)-,& ("2,#,) #"#"$%

+1)*"1 ,&. #"#"$% %$$$)$)-,& ("2,#,) #"#"$% ("0%&."15

2. Set the voltage of the a.c. power supply to 2 V.

Q"-,+0,& 64$-,& 2,#) 2"0,$,& 0%,(, ,5%5 +,., "&5

3. Switch on the power supply and record the

readings of both of the voltmeters. ;).%+0,& 2"0,$,& 0%,(, .,& 1"04.0,& 2,>,,& 0".%,=.%,

64$-*"-"15

4. Repeat steps 2 and 3 with the 900 turns coil as the secondary coil.

B$, $,,7=$,,7 O .,& T .",& #"#"$% 1$$$)$)-,& ("2,#,) #"#"$% ("0%&."15

5. Change the set-up of the apparatus so that the 900 turns coil becomes the primary co

while the 600 turns coil becomes the secondary coil. Q%0,1 (%(%&,& 1,.,( (%+,8, #"#"$% 1$$ $)$)-,& *"&:,.) #"#"$% +1)*"1 *,&,0,$, #"#"$% %$$ $)$)

*"&:,.) #"#"$% ("0%&."15 6. Set the voltage of the power supply to 10 V.

Q"-,+0,& 64$-,& 2,#) 2"0,$,& 0%,(, +,., '$&5

7. Switch on the power supply and record the readings of both of the voltmeters.

;).%+0,& 2"0,$,& 0%,(, .,& 1"04.0,& 2,>,,& 0".%,=.%, 64$-*"-"15

8. Repeat steps 6 and 7 with the 300 turns coil as the secondary coil.

B$, $,,7=$,,7 Y .,& ` .",& #"#"$% ($$$)$)-,& ("2,#,) #"#"$% ("0%&."15

Method 1. The apparatus was set up as shown in the diagram. The 300 turns copper coil was the prima

coil and the 600 turns coil was the secondary coil.

2. The voltage of the a.c. power supply was set to 2 V.

3. The power supply was switched on and the readings of the voltmeters were recorded.

4. Steps 2 and 3 were repeated with the 900 turns coil as the secondary coil.

5. The set-up of the apparatus was changed so that the 900 turns coil became the primary c

while the 600 turns coil became the secondary coil.

Aim

Voltmeter

VoltmeterVoltmeter

Voltmeter

a.c. power supply

Bekalan kuasa a.u.

Copper coil

Gegelungkuprum

C-shaped iron core

Teras besi berbentu

AC/DC L.T. POWER SUPPLY 10Amp

V

V

Learning Outcome

State that

VP

VS

=N

P

NS

for an ideal transformer.


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95

6. The voltage of the power supply was set to 10 V.

7. The power supply was switched on and the readings of the voltmeters were recorded.

8. Steps 6 and 7 were repeated with the 300 turns coil as the secondary coil.

Number of

turns of the

primary coil:$&"-,"- &$&$/"-

,+,+&'-, 9($4+(E

NP

Number of

turns of the

secondary coil:$&"-,"- &$&$/"-

,+,+&'-, )+6'-2+(E

NS

Input

voltage for

the primary

coilF1&/"- $-9'/

.",$ ,+,+&'-,

9($4+(E VP/ V

Output

voltage for

the secondary

coilF1&/"- 1'/9'/ .",$

,+,+&'-, )+6'-2+(E

Vs/ V

NP

NS

VP

VS

300 600 2.0 3.9 0.50 0.5

300 900 2.0 5.8 0.33 0.34

900 600 10.0 6.6 1.50 1.52

900 300 10.0 3.3 3.00 3.0

Note: Write the ratiosN

P

NS

andVP

VS

to two decimal places.

K4-, a Q%$)(0,& &)(2,7K

@

K9

.,&b

@

b9

0"+,., .%, -"*+,- +"1+%$%7,&5

Discussion 1. From the readings taken, compare the ratios ofN

P

NS

andVP

VS

for each pair of primary coil

secondary coils.

J,1)+,., 2,>,,& 8, .),*2)$3 2,&.),& &)(2,7K

@

K9

.,&b

@

b9

2,#) ("-),+ +,(,,& #"#"$% +1)*"

#"#"$% ("0%&."15D-79210)* 2)3 4-)+125+0)* = /"-1.%)(%!*.% ).% -"-

The ratios are approximately equal.

2. Taking into account experimental errors, make an inference on the relationship betwN

P

NS

andVP

VS

.

J",& *",*2)$ 0)1, 1,$,- "0(+"1)*"&3 &8,-,0,& )"/')&H"1"&( 2,#) 7%2%,& ,&-,1,K

@

K9

.",&b

@

b9

5

>2?0)* 0).(1()4(5 = /"-1$.+

VP

VS

=N

P

NS

Conclusion The ratio of the primary input voltage to the secondary output voltage is equal to the ra

the number of turns in the primary coil to the number of turns in the secondary coil.

Precautions 1. Ensure that the connections at the ends of the connecting wires are tight and have

electrical contact.

2. The C-shaped soft iron cores are clipped tightly to reduce leakage of magnetic flux.

Observations


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!"#$!%&!"#+ A model of electricity transmission

Model penghantaran elektrik Inquiry-Discov

Aim To study the model of electricity transmissionApparatus

A 1:20 step-up transformer, a 20:1 step-down transformer, four 12 V 24 W bulbs, two sets of apower supply, four retort stands and power line terminal rods

Q1,&(H41*"1 )&:,0 &,)0 '2"$3 -1,&(H41*"1 )&:,0 -%1%& "$2'3 "*+,- *"&-4$ '"&"!33 .%, ("- 2"0,$,& 0%,(, ,5%53 "*

0,0) 1"-41- .,& 14. -"1*)&,$ -,$),& 0%,(,

Materials Insulated eureka wire (s.w.g. 30) to be used as transmission lines and connecting wires

J,/,) "%1"0, 2"1+"&"2,-/4,5,6, ($0%&-%0 .)#%&,0,& ("2,#,) -,$),& +",&-,1,& .,& .,/,) +"&8,*2%

Procedure 1. Set up the electricity transmission models,Aand Bas shown in the diagram.

9".),0,& *4."$ +",&-,1,& "$"0-1)03 F .,& I3 ("+"1-) 8, .)-%&:%00,& .,$,* 1,:,75

Power line

terminal rodRod terminaltalian kuasa

12 V 24 W

12 V 24 W

"Residential area"

Kawasan perumahan

"Power station"(12 V a.c. power supply)

Stesen kuasa(Bekalan kuasa 12 Va.u.)

Transmission line(4 m long)

Talian penghantaran(Panjang 4 m)

"Residential area"

Kawasan perumahan

"Power station"(12 V a.c. power supply)

Stesen kuasa(Bekalan kuasa 12 Va.u.)

Transmission line(4 m long)

Talian penghantaran(Panjang 4 m)

1:20 step-uptransformer

Transformer

injak naik 1:20

12 V 24 W

20:1 step-downtransformer

Transformer

injak turun 20:1

Power line terminal rod

Rod terminal talian kuasa

12 V 24 W

Model A / A4."$ F Model B / A4."$ I

2. Switch on the 12 V a.c. power supply in modelAand model B.

;).%+0,& 2"0,$,& 0%,(, ,5%5 '"&.,$,* *4."$ F .,& *4."$ I5

3. Observe and compare the brightness of the bulbs at the power station end and t

residential area end for models Aand B respectively.

@"17,-)0,& .,& 2,&.),& 0">"1,7,& *"&-4$=*"&-4$ .) 7%:% P(-"("& 0%,(,R .,& .) 7%:% P0,/,(

+"1%*,7,&R 2,#) *4."$ F ,&. I *,()=*,()


2. The 12 V a.c. power supply in modelAand model Bwas switched on.

3. The brightness of the bulbs at the power station end and the residential area end we

compared for models Aand B.

Learning Outcome

! G(384( +,( 23

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97

Power transmission

model312+& 9+-,7"-/"("- 6'")"

Brightness of bulb at

power station?+@+("7"- 4+-/1& 2$ G)/+)+- 6'")"H

Brightness of bulb at

residential area?+@+("7"- 4+-/1& 2$ G6"#")"-

9+('4"7"-H

A Bright Dim

B Bright Bright

Discussion 1. Relate the brightness of the bulbs to the power at the power station end and the p

delivered to the residential area end.

;%2%,)-0,& 0">"1,7,& *"&-4$ .",& 0%,(, .) 7%:% P(-"("& 0%,(,R .,& 0%,(, 8, .)2"0,$0,& .) 7

P0,/,(,& +"1%*,7,&R5 @('2+0)* = /"%!4$1$%

The brightness of the bulb at the power station end indicates the power supplied by

power station to the transmission lines. The brightness of the bulb at the residential

end indicates the power delivered by the transmission lines to the residential area.

2. Compare the voltage of the transmission lines of models Aand B.

I,&.),& 64$-,& 2,#) -,$),& +",&-,1,& 2,#) *4."$ F .,& *4."$ I5

D-79210)* 2)3 4-)+125+0)* = /"-1.%)(%!*.% ).% -"-

The voltage of transmission lines of model Bis higher than that of model A.

3. Which model transmits electricity with less loss of power to the residential area?

A4."$ 8, *,&,0,7 *",&-,1 "$"0-1)0 .",& 0"7)$,,& 0%,(, 8, $"2)7 0">)$ 0" 0,/,(,& +"1%*,7

A1(304+0)* =

ModelB

Conclusion Electricity is transmitted with less loss of power when the voltage of transmission lines is hi

Precaution Be careful not to touch the transmission lines in model Bwhich has a higher voltage.

Observations


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Physics Form 5 Chapter 3 Electromagnetism

98

Objective Questions

Choose the best option for eachquestion.

8(#(4 7(#(4.% 9.%! "#$%&'(1.!( &"+(.7 &'.#.%:

1. Diagram 1 shows a magnetic fieldproduced by an electric current.

;.5.4 < -"%$%5$**.% -").% -.!%"+9.%! )(4.&(#*.% '#"4 &$.+$ .,$&

"#"*+,(*:

P

Diagram 1 /Rajah 1

Which is the direction of thecurrent at pointP?=.%! -.%.*.4 -",$7.*.% .,.4 .,$&

7.). +(+(* 8>

A C

B D

2. Diagram 2 shows the apparatusset-up to observe the magnetic fielddue to a current in a circular coil.

;.5.4 ? -"%$%5$**.% &$&$%.% ,.).&$%+$* -"-",4.+(*.% -").% -.!%"+

9.%! )(&"1.1*.% .,$& ).#.- !"!"#$%!

1$#.+:

Diagram 2 /Rajah 2

Which diagram shows the magneticfield correctly?;.5.4 9.%! -.%.*.4 -"%$%5$**.%

-").% -.!%"+ )"%!.% 1"+$#>

A

B

C

D

3. Diagram 3 shows an electromagnet. ;.5.4 @ -"%$%5$**.% "#"*+,'-.!%"+:

Soft iron core

Teras besilembut

Y

X

Diagram 3 /Rajah 3

What are the directions shown bythe pointers of the compassesXand Y?

A,.4B.,.4 9.%! -.%.*.4 )(+$%5$**.%

'#"4 7"%$%5$* 1.!( *'-7.&B*'-7.&

C ).% =>

A X

Y

CX

Y

BX

Y

DX

Y

4. Diagram 4 shows an electromagne ;.5.4 D -"%$%5$**.% "#"*+,'-.!%"+

X

Diagram 4 /Rajah 4

What is the change in the strengthof the magnetic field atXwhen thsoft iron core is pulled out of thecoil?

A7.*.4 7",$1.4.% *"*$.+.% -").%

-.!%"+ )( C .7.1(#. +",.& 1"&( #"-1

)(+.,(* *"#$., ).,(7.). !"!"#$%! (+$>

A Increases E",+.-1.4

B Decreases E",*$,.%!

C Increases and then decreases E",+.-1.4 ).% *"-$)(.%

1",*$,.%!

D No change F(.). 7",$1.4.%

5. A current-carrying conductor isplaced in a magnetic field. Whichof the following situations willresult in a force acting on the

conductor? G$.+$ *'%)$*+', 9.%! -"-1.H. .,

)(#"+.**.% ).#.- -").% -.!%"+:

G(+$.&( 9.%! -.%.*.4 -"%!.*(1.+*

&$.+$ ).9. 1",+(%).* 7.). *'%)$*+'

(+$>

A Direction of current same as tdirection of magnetic field

A,.4 .,$& &.-. )"%!.% .,.4-").% -.!%"+

B Direction of current opposite the direction of magnetic field

A,.4 .,$& 1",+"%+.%!.% )"%!.%.,.4 -").% -.!%"+

C Direction of current

perpendicular to direction ofmagnetic field

A,.4 .,$& 1",&","%5.%! )"%!.%.,.4 -").% -.!%"+

!"#$%&' )*%&+,#%


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Physics Form 5 Chapter 3 Electromagnetis

99

6. Which of the following shows thecombined magnetic field whena current-carrying wire is placedbetween a pair of magnadurmagnets?

A%+.,. 9.%! 1",(*$+I 9.%! -.%.*.4-"%$%5$**.% -").% -.!%"+

1",!.1$%! .7.1(#. &.+$ ).H.( 9.%!-"-1.H. .,$& )(#"+.**.% )( .%+.,.

&"7.&.%! -.!%"+ -.!%.)$,>

A

N/

US

B

SN/

U

C

SN/

U

D

SN/

U

7. Diagram 5 shows a current-carryingwire and two permanent magnets.

;.5.4 J -"%$%5$**.% ).H.( 9.%!-"-1.H. .,$& ).% )$. -.!%"+

*"*.#:

Power supply

Bekalan kuasa

Wire

Dawai

Q

P

X YSN / U

Diagram 5 /Rajah 5

What is the type of current in the

wire and in which direction shouldit be placed so that a net force isexerted on the wire?

A7.*.4 5"%(& .,$& ).#.- ).H.( ).% )(

.,.4 9.%! -.%.*.4 ).H.( (+$ 4.,$&

)(#"+.**.% &$7.9. &.+$ ).9. 7.)$.%

1",+(%).* 7.). ).H.( (+$>

Type of current)#*'+ &$,+

Direction-$&.

A Direct currentA,$& +",$&

AlongPQG"7.%5.%! 8K

B Direct currentA,$& +",$&

AlongXYG"7.%5.%! C=

C Alternatingcurrent

A,$& $#.%!B.#(*

AlongPQG"7.%5.%! 8K

D Alternatingcurrent

A,$& $#.%!B.#(*

AlongXYG"7.%5.%! C=

8. Diagram 6 shows a left hand whichrepresents the Fleming Left-HandRule.

;.5.4 L -"%$%5$**.% +.%!.% *(,( 9.%!-"H.*(#( 8"+$. F.%!.% M(,( N#"-(%!:

8

Diagram 6 /Rajah 6

Prepresents the8 -"H.*(#(

A motion!",.*.%

B current .,$&

C magnetic field -").% -.!%"+

9. Diagram 7 shows a direct currentmotor.

;.5.4 O -"%$%5$**.% -'+', .,$& +",$&:

Carbonbrush

Beruskarbon

Magnet

Magnet

Commutator

Komutator

Wire coil

Gegelung dawai

SF

F

N /U

Diagram 7 /Rajah 7

Which action will make themagnitude of forceFsmaller?F(%).*.% 9.%! -.%.*.4 .*.%

-"%9"1.1*.% -.!%(+$) ).9. N

-"%5.)( #"1(4 *"0(#>

A Increase the number of turthe wire coil

/"%.-1.4*.% 1(#.%!.% #(#(+.!"!"#$%! ).H.(

B Increase the magnitude of electric current

/"%.-1.4*.% -.!%(+$) .,$

"#"*+,(*

C Increase the strength of themagnetic field

/"%.-1.4*.% *"*$.+.% -"

-.!%"+

D Increase the resistance of tcoil

/"%.-1.4*.% ,(%+.%!.% !"!

10. Diagram 8 shows a transforme

supplying a voltage to light upbulb at normal brightness. ;.5.4 P -"%$%5$**.% &.+$ +,.%&

9.%! -"-1"*.#*.% Q'#+.% $%+$*

-"%9.#.*.% -"%+'# 7.). *"0",.

%',-.#:

240 V

6 AIp

Diagram 8 /Rajah 8

What is currentIP?

E",.7.*.4 .,$& R8>

A 0.2 A C 8.0 A

B 0.6 A D 30.0 A

11. What are the characteristics ofthe voltage and current in powtransmission cables?

A7.*.4 0(,(B0(,( Q'#+.% ).% .,$& )

*.1"# 7"%!4.%+.,.% *$.&.>

Voltage/01"&*

Curre-$,+

A Low voltageS'#+.% ,"%).4

DirectF",$&

B Low voltage

S'#+.% ,"%).4

Alternatin

T#.%!B.#(*

C High voltageS'#+.% +(%!!(

DirectF",$&

D High voltageS'#+.% +(%!!(

AlternatinT#.%!B.#(*


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100

12. Diagram 9 shows an electriccircuit consisting of a step-downtransformer and two identicalvoltmeters V

1and V

2.

;.5.4 U -"%$%5$**.% &.+$ #(+., "#"*+,(*

9.%! -"%!.%)$%!( &.+$ +,.%&3',-",(%5.* +$,$% ).% )$. Q'#+-"+", 9.%!

&",$7. SH

).% SI

:

SH

SIJ

Diagram 9 /Rajah 9

Which comparison of the readingof voltmeters V

1and V

2is correct?

8",1.%)(%!.% 9.%! -.%.*.4 1"+$#

+"%+.%! 1.0..% Q'#+-"+", SH32) SI>A V

1V

2

B V1= V

2

C V1V

2

13. Which of the following is theoutput of a direct current generator?

A%+.,. 9.%! 1",(*$+I 9.%! -.%.*.4-",$7.*.% '$+7$+ 7"%5.%. .,$& +",$&>

A

0

V

t

B

0

V

t

C

0

V

t

D

0

V

t

14. What is the type of material in thelaminated core of a transformerand what is the function of thelamination?

A7.*.4 5"%(& 1.4.% 1.!( +",.&

1",#.-(%. +,.%&3',-", ).% .7.*.43$%!&( #.-(%. (+$>

Type ofmaterial

)#*'+ %&.&*

Function oflamination

2,*3+' 1&4'*&

A Soft ironE"&( #"-1$+

To increaseeddy currentT%+$*

-"%.-1.4*.%.,$& 7$&.,

B Soft ironE"&( #"-1$+

To reduce eddycurrentT%+$*

-"%!$,.%!*.%

.,$& 7$&.,

C SteelM"#$#(

To increaseeddy currentT%+$*

-"%.-1.4*.%

.,$& 7$&.,

D SteelM"#$#(

To reduce eddycurrentT%+$*

-"%!$,.%!*.%

.,$& 7$&.,

15. Diagram 10 shows a copper rodplaced inside a magnetic field.

;.5.4

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101

Subjective Questions

Section A / 5&.&3'&* -

1. Diagram 1 shows a circuit that can switch on the startermotor of a car by turning the key at the key-operatedswitch.

;.5.4 < -"%$%5$**.% &.+$ #(+., 9.%! 1'#"4 -"%!4()$7*.%

-'+', 7"%!4()$7 1.!( &"1$.4 *","+. )"%!.% -"-$+.,*.%*$%0( 7.). &$(& *"%).#(.% *$%0(:

+

Key

KunciSpring

Spring

Soft iron plate

Plat besi lembutContacts

Sesentuh

Soft iron core

Teras besi lembutStarter motor

Motor penghidup

Battery

Bateri

Key-operated switch

Suis kendalian kunci

Diagram 1 /Rajah 1

(a) Describe what happens to each of the following partswhen the key-operated switch is turned on:

W$,.(*.% .7. 9.%! .*.% 1",#.*$ 7.). 1.4.!(.% 1",(*$+

.7.1(#. &$(& *"%).#(.% *$%0( )(4()$7*.%X

(i) the coil around the soft iron core !"!"#$%! +",.& 1"&( #"-1$+ [1 mark / H-.,*.4]

(ii) the soft iron core +",.& 1"&( #"-1$+ [1 mark / H-.,*.4]

(iii) the soft iron plate 7#.+ 1"&( #"-1$+ [1 mark / H-.,*.4]

(iv) the contacts &"&"%+$4 [1 mark / H-.,*.4]

(b) What is the effect on the starter motor if more turnsare added to the coil round the soft iron core? Explainyour answer.

A7.*.4 *"&.% -'+', 7"%!4()$7 5(*. #"1(4 1.%9.* #(#(+.%

)(+.-1.4 *"7.). !"!"#$%! )( &"*"#(#(%! +",.& 1"&( #"-1$+>

F",.%!*.% 5.H.7.% .%).: [2 marks / I-.,*.4]

(c) State oneadvantage of using such a system to startthe car engine.

Y9.+.*.% +&",*"1.(*.% -"%!!$%.*.% &(&+"- &")"-(*(.%$%+$* -"%!4()$7*.% "%5(% *","+.: [2 marks / I-.,*.4]

2. Diagram 2 shows a steel rod,XYon bare copper tracks. ;.5.4 ? -"%$%5$**.% &"1.+.%! ,') *"#$#(I C= )( .+.& #.%).&.%

*$7,$- +.%7. 7"%"1.+:

N/U

S

X

Y

Diagram 2 /Rajah 2

(a) In Diagram 2, mark the direction of Z.#.- ;.5.4 ?I +.%).*.% .,.4 1.!(

(i) the current in the steel rod .,$& ).#.- ,') *"#$#( [1 mark / H-

(ii) the motion of the steel rod !",.*.% ,') *"#$#( (+$ [1 mark / H-

(b) Explain why the steel rod moves in the directionmarked in (a)(ii).

F",.%!*.% -"%!.7. ,') *"#$#( 1",!",.* *" .,.4 9.%)(+$%5$**.% )( [.\[((\: [3 marks / K-

(c) State oneway to reverse the direction of motion the steel rod.

Y9.+.*.% +&",0.,. $%+$* -"%9'%!&.%!*.% .,.4 !",') *"#$#( (+$: [1 mark / H-

(d) (i) What change will be observed if the steel rodreplaced by an aluminium rod of the same siz

A7.*.4 7",$1.4.% 9.%! .*.% )(7",4.+(*.% 5(*.

,') *"#$#( )(!.%+(*.% )"%!.% ,') .#$-(%($- 9.%!

-"-7$%9.( &.(6 9.%! &.-.> [1 mark / H-

(ii) Explain your answer in (d)(i).

F",.%!*.% 5.H.7.% .%). )( [)\[(\:[3 marks / K-

3. Diagram 3 shows a pendulum oscillating between thepoles of a magnet. The pendulum is made up of a coprod and a brass bob.

;.5.4 @ -"%$%5$**.% 1.%)$# 9.%! &").%! 1",.9$% )( .%*$+$1B*$+$1 -.!%"+: E.%)$# (+$ +",)(,( ).,(7.). &"1.+.%!

*$7,$- ).% &"1(5( #.)$%! #'9.%!:

G

0

+

N

U/

S

Q

P

O

Brass bobLadung loyang

Copper rod

Rod kuprum

Switch

Suis

Diagram 3 /Rajah 3

(a) (i) What is electromagnetic induction?

A7.*.4 .,$4.% "#"*+,'-.!%"+> [1 mark / H-


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102

(ii) Use a t to indicate whether e.m.f. and/orcurrent is induced in the copper rod when theswitch is off and when the switch is on.

]$%.*.% t$%+$* -"%$%5$**.% &.-. .). ):!:":).%^.+.$ .,$& )(.,$4*.% ).#.- ,') *$7,$- .7.1(#.

&$(& )(-.+(*.% ).% .7.1(#. &$(& )(4()$7*.%:

Switch OFF

G$(& )(-.+(*.% Induced e.m.f.

):!:": +",.,$4

Induced currentA,$& +",.,$4

Switch ONG$(& )(4()$7*.%

Induced e.m.f.):!:": +",.,$4

Induced currentA,$& +",.,$4

[4 marks / L-.,*.4]

(iii) Describe the motion of the galvanometer pointer

when the switch is ON.W$,.(*.% !",.*.% 7"%$%5$* !.#Q.%'-"+", .7.1(#.

&$(& )(4()$7*.%: [1 mark / H-.,*.4]

(iv) Mark on Diagram 3 the direction of the currentin the copper rod when the rod is swinging fromQto O.

F.%).*.% 7.). ;.5.4 @ .,.4 .,$& ).#.- ,') *$7,$-

.7.1(#. ,') (+$ &").%! 1",.9$% ).,( K *" _:

[1 mark / H-.,*.4]

(b) When the switch is ON, the oscillation stops after ashort while. Explain this observation.

A7.1(#. &$(& )(4()$7*.%I .9$%.% 1",4"%+( &"#"7.& -.&.

9.%! &(%!*.+: F",.%!*.% 7"-",4.+(.% (%(:

[4 marks / L-.,*.4]

Section B / 5&.&3'&* 5

4. A student investigated how three transformers step downthe voltage of an alternating current supply to light up abulb.

G"',.%! -$,() -"%!*.5( 1.!.(-.%. +(!. +,.%&3',-",

-"%$,$%*.% Q'#+.% 1.!( &$.+$ 1"*.#.% .,$& $#.%!B.#(* $%+$*-"%9.#.*.% -"%+'#:

Diagrams 4.1 to 4.3 show the three different arrangements,P, QandRset up by the student.

;.5.4B,.5.4 D:< 4(%!!. D:@ -"%$%5$**.% +(!. &$&$%.%I 8I K

).% ; 9.%! )(&")(.*.% '#"4 -$,() (+$:

400 turns

400 lilitan

20 turns

20 lilitan

12 V 24 W bulb

Mentol 12 V24 W

Normal brightness

Kecerahan normal

240 Valternatingcurrent

Arus ulang-alik 240 V

Arrangement P

Susunan P

Diagram 4.1 /Rajah 4.1

500 turns

500 lilitan

25 turns

25 lilitan

12 V 24 W bulb

Mentol 12 V24

Normal brightne

Kecerahan norm



Arrangement Q

Susunan Q


900 turns

900 lilitan

30 turns

30 lilitan

12 V 24 W bulb

Mentol 12 V24

Dim

Malap



Arrangement R

Susunan R


(a) (i) What is a step-down transformer? A7.*.4 +,.%&3',-", (%5.* +$,$%> [1 mark / H-.,*

(ii) Compare the ratio of the primary turns to thesecondary turns and the brightness of the bulbsarrangementsPand Q. Compare also the ratio the primary turns to the secondary turns and thbrightness of the bulbs in arrangements Qand

E.%)(%!*.% %(&1.4 #(#(+.% 7,(-", *"7.). #(#(+.%&"*$%)", ).% *"0",.4.% -"%+'# ).#.- &$&$%.%

8 ).% K: E.%)(%!*.% 5$!. %(&1.4 #(#(+.% 7,(-",*"7.). #(#(+.% &"*$%)", ).% *"0",.4.% -"%+'# ).#.

&$&$%.% K ).% ; [3 marks / K-.,*

(iii) Relating the ratio of the primary turns to thesecondary turns to the brightness of the bulbs,deduce a relationship between the ratio of theprimary turns to the secondary turns and the

output voltage of the transformer. Z"%!.% -"%!4$1$%!*.(+*.% %(&1.4 #(#(+.% 7,(-",

*"7.). #(#(+.% &"*$%)", )"%!.% *"0",.4.% -"%+'#I

)")$*&(*.% +&",4$1$%!.% .%+.,. %(&1.4 #(#(+.%

7,(-", *"7.). #(#(+.% &"*$%)", )"%!.% Q'#+.% '$+7

+,.%&3',-",: [3 marks / K-.,*

(b) Explain how a transformer uses the magnetic effectan electric current and electromagnetic induction toproduce a voltage at its output terminals.

F",.%!*.% 1.!.(-.%. +,.%&3',-", -"%!!$%.*.% *"&.%-.!%"+ .,$& "#"*+,(* ).% .,$4.% "#"*+,'-.!%"+ $%+$*-"%!4.&(#*.% Q'#+.% 7.). +",-(%.# '$+7$+%9.:

[4 marks / L-.,*

(c) The student would like to modify arrangementPto produce a 3600 V output with minimum loss of

power. Explain the modifications that need to be mato achieve this purpose.

/$,() (+$ (%!(% -"%!$1.4&$.( &$&$%.% 8 $%+$*-"%!4.&(#*.% '$+7$+ KMNNO)"%!.% *"4(#.%!.% *$.&.

-(%(-$-: F",.%!*.% 7"%!$1.4&$.(.% 9.%! 7",#$

)(#.*$*.% $%+$* -"%0.7.( +$5$.% (%(:[10 marks / HN-.,*


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103

Section C / 5&.&3'&* 6

5. (a) (i) What is meant by electromagnetic induction? A7.*.4 9.%! )(-.*&$)*.% )"%!.% .,$4.%

"#"*+,'-.!%"+> [1 mark / H-.,*.4]

(ii) With the aid of diagrams, explain how a constantcurrent can be induced in a piece of straight

copper rod. Z"%!.% 1.%+$.% !.-1., ,.5.4I +",.%!*.% 1.!.(-.%.

.,$& 9.%! -.#., 1'#"4 )(.,$4*.% ).#.- &"1.+.%! ,')

*$7,$- #$,$&: [4 marks / L-.,*.4]

(b) You are asked to study the features of five generatorsas shown in Diagrams 5.1 to 5.5. One of thegenerators will be used to supply a large current toproduce high frequency vibrations in a vibratingmachine.

A%). )(-(%+. -"%!*.5( 0(,(B0(,( #(-. 7"%5.%. &"7",+( 9.%!)(+$%5$**.% ).#.- ;.5.4 J:< 4(%!!. ;.5.4 J:J: G.+$

).,(7.). 7"%5.%. (+$ .*.% )(!$%.*.% $%+$* -"-1"*.#*.%

.,$& 9.%! 1"&., $%+$* -"%!4.&(#*.% !"+.,.% 1",3,"*$"%&(

+(%!!( ).#.- -"&(% 1",!"+.,:

Explain the suitability of each feature in Diagrams 5.1to 5.5 and then determine the most suitable generator.

F",.%!*.% *"&"&$.(.% &"+(.7 0(,( ).#.- ;.5.4 J:< 4(%!!.;.5.4 J:J ).% *"-$)(.% +"%+$*.% 7"%5.%. 9.%! 7.#(%!

&"&$.(:

Give a reason for you choice. E",(*.% +&",&"1.1 1.!( 7(#(4.% .%).:

[10 mark / HN-.,*.4]

P

Number of turns of coil = 400E(#.%!.% #(#(+.% !"!"#$%!

Speed of rotation of coil: Low`.5$ !"!"#$%!X ;"%).4


N/

U

SAB

-

+

Rotation

Putaran

Carbon brush

Berus karbon

Commutator

Komutator

Vibrating machine

Mesin penggetar

Q

Number of turns of c

E(#.%!.% #(#(+.% !"!"#

= 400

Speed of rotation of

E(#.%!.% #(#(+.% !"!"#HighF(%!!(


R

Number of turns of c

E(#.%!.% #(#(+.% !"!"#

= 900

Speed of rotation of

`.5$ 7$,.+. !"!"#$%!

HighF(%!!(


S

Number of turns of coil = 900 Speed of rotation of coil: E(#.%!.% #(#(+.% !"!"#$%! `.5$ 7$,.+. !"!"#$%!X F(%!


N/

U

SAB

-

+

Rotation

Putaran

Carbon brush

Berus karbon

Commutator

Komutator

Vibrating machine

Mesin penggetar

N/

U

SAB

Rotation

Putaran

Carbon brushes

Berus karbon

Slip rings

Gelang

gelincir

Vibrating machine

Mesin penggetar

N/

U

SA

B

Rotation

Putaran

Carbon brushes

Berus karbon

Slip rings

Gelang

gelincir

Vibrating machine

Mesin penggetar


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104

T

Number of turns of coil = 900 Speed of rotation of coil: LowE(#.%!.% #(#(+.% !"!"#$%! `.5$ !"!"#$%!X ;"%).4


N/

U

SA

B

Rotation

Putaran

Carbon brushes

Berus karbon

Slip rings

Gelanggelincir

Vibratingmachine

Mesinpenggetar

(c) (i) 400 kW of electrical power is to be transmittedby cables which have a total resistance of 50 !.Calculate the power loss due to heating of thecables if the power is transmitted at a voltage

160 kV. M$.&. "#"*+,(* DVV ?P.*.% )(4.%+., '#"4 *.1"# 9.%

-"-7$%9.( 5$-#.4 ,(%+.%!.% QN!: W(+$%! *"4(#.%!

*$.&. )(&"1.1*.% '#"4 7"-.%.&.% *.1"# 5(*. *$.&.(+$ )(4.%+., 7.). Q'#+.% HMN?O:

[4 marks / L-.,*

(ii) Suggest one feature of the power cable thatwill reduce the amount of power loss duringtransmission of electricity.

a.).%!*.% +&", 0(,( *.1"# *$.&. 9.%! .*.%-"%!$,.%!*.% 5$-#.4 *"4(#.%!.% *$.&. &"-.&.

7"%!4.%+.,.% "#"*+,(*: [1 mark / < -.,*

Written Practical

Section A / 5&.&3'&* -

1. A student carries out an experiment to study the relationship between the induced current,I, in a solenoid and the numberturns,N, of the solenoid using an experimental set-up as shown in Diagram 1.1. A bar magnet was pushed at a certain speed ina solenoid ofN= 20 and the maximum reading,I, on a microammeter was observed. The procedure was repeated with N= 60, 80 and 100 using different solenoids.

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&'#"%'() (+$ )"%!.% -"%!!$%.*.% &$&$%.% ,.).& "*&7",(-"% &"7",+( 9.%! )(+$%5$**.% ).#.- ;.5.4

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Diagrams 1.2, 1.3, 1.4, 1.5 and 1.6 show the scale of the microammeter for each value of N.;.5.4

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Section B / 5&.&3'&* 5

2. Diagram 2 show two similar electric bells,Aand B. The same current flows through both bells. Bell Ahas more turns of wand produces a louder ring. Bell Bhas less turns of wire and produces a softer ring.

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Based on the information and observations:E",).&.,*.% -.*#$-.+ ).% 7"-",4.+(.% (+$X

(a) State one suitable inference.Y9.+.*.% +&", (%3","%& 9.%! &"&$.(: [1 mark / H -.,*

(b) State onesuitable hypothesis.Y9.+.*.% +&",4(7'+"&(& 9.%! &"&$.(: [1 mark / H -.,*

(c) With the use of apparatus such as a soft iron core, insulated copper wire, pins and other apparatus, describe oneexperimto investigate the hypothesis stated in 2(b).

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In your description, state clearly the following: Z.#.- 7"%",.%!.% .%).I %9.+.*.% )"%!.% 5"#.& 7",*.,. 1",(*$+X

(i) The aim of the experiment F$5$.% "*&7",(-"%

(ii) The variables in the experiment 8"-1'#"4 $1.4 ).#.- "*&7",(-"%

(iii) The list of apparatus and materials G"%.,.( ,.).& ).% 1.4.%

(iv) The arrangement of the apparatus G$&$%.% ,.).&

(v) The procedure of the experiment which includes onemethod of controlling the manipulated variable and one methof measuring the responding variable.

8,'&")$, "*&7",(-"%I +",-.&$* +&", *.").4 -"%!.H.# 7"-1'#"4 $1.4 )(-.%(7$#.&(*.% ).% +&", *.").4 -"%!$*$, 7"-1'$1.4 1",!",.* 1.#.&:

(vi) The way to tabulate the data a.,. $%+$* -"%5.)$.#*.% ).+.

(vii) The way to analyse the data a.,. $%+$* -"%!.%.#(&(& ).+. [10 marks / HN -.,*

Documents

PB165242 PG068 – PG106