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1 John Parkinson John Parkinson © ©

1 John Parkinson © 2 THE AURORA The Aurora Borealis, the Northern Lights and the Aurora Australis, the Southern lights are phenomena resulting from the

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Page 1: 1 John Parkinson © 2 THE AURORA The Aurora Borealis, the Northern Lights and the Aurora Australis, the Southern lights are phenomena resulting from the

1

John Parkinson John Parkinson ©©

Page 2: 1 John Parkinson © 2 THE AURORA The Aurora Borealis, the Northern Lights and the Aurora Australis, the Southern lights are phenomena resulting from the

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THE AURORA

The Aurora Borealis, the Northern Lights and the Aurora Australis, the Southern lights are phenomena

resulting from the interaction between Solar Wind and the Earth’s magnetic field.

Page 3: 1 John Parkinson © 2 THE AURORA The Aurora Borealis, the Northern Lights and the Aurora Australis, the Southern lights are phenomena resulting from the

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N S

Lines of magnetic flux, Φ

Magnetic flux density, B, measures the strength of the magnetic field.

B = number of lines of flux per square metre

AB

UNITS are Webers per square metre Wb m-2 or TESLAS (T)

B IS A VECTOR QUANTITY

Page 4: 1 John Parkinson © 2 THE AURORA The Aurora Borealis, the Northern Lights and the Aurora Australis, the Southern lights are phenomena resulting from the

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N S

Lines of magnetic flux, Φ

AB

A

Total magnetic flux through area A is given by:

Φ = B A webers, when the area is perpendicular to the field

Φ = B A sinθ

Page 6: 1 John Parkinson © 2 THE AURORA The Aurora Borealis, the Northern Lights and the Aurora Australis, the Southern lights are phenomena resulting from the

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1820Professor Oersted was demonstrating an experiment for students when he accidentally discovered that a compass needle moved when it was close to a wire connected to a battery.

Professor Hans Christian Oersted

Page 7: 1 John Parkinson © 2 THE AURORA The Aurora Borealis, the Northern Lights and the Aurora Australis, the Southern lights are phenomena resulting from the

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B

I

Page 8: 1 John Parkinson © 2 THE AURORA The Aurora Borealis, the Northern Lights and the Aurora Australis, the Southern lights are phenomena resulting from the

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I

B

Page 9: 1 John Parkinson © 2 THE AURORA The Aurora Borealis, the Northern Lights and the Aurora Australis, the Southern lights are phenomena resulting from the

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RIGHT HAND GRIP RULE:

I

Page 10: 1 John Parkinson © 2 THE AURORA The Aurora Borealis, the Northern Lights and the Aurora Australis, the Southern lights are phenomena resulting from the

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current outwards current inwards

r

B

r

IB

20

-

Page 11: 1 John Parkinson © 2 THE AURORA The Aurora Borealis, the Northern Lights and the Aurora Australis, the Southern lights are phenomena resulting from the

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length l

IN turns

In the middle

l

NIB 0

at the end l

NIB

20

Page 12: 1 John Parkinson © 2 THE AURORA The Aurora Borealis, the Northern Lights and the Aurora Australis, the Southern lights are phenomena resulting from the

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N S

Interaction between a magnet and the field due to a current

N S

Page 13: 1 John Parkinson © 2 THE AURORA The Aurora Borealis, the Northern Lights and the Aurora Australis, the Southern lights are phenomena resulting from the

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N S

F

Page 14: 1 John Parkinson © 2 THE AURORA The Aurora Borealis, the Northern Lights and the Aurora Australis, the Southern lights are phenomena resulting from the

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FLEMING’S LEFT HAND MOTOR RULE

FOREFINGER = FIELD

THUMB = MOTION

SECOND FINGER = CURRENT

Page 15: 1 John Parkinson © 2 THE AURORA The Aurora Borealis, the Northern Lights and the Aurora Australis, the Southern lights are phenomena resulting from the

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FLEMING’S LEFT HAND MOTOR RULE

FOREFINGER = FIELD

THUMB = MOTION

SECOND FINGER = CURRENT

Page 16: 1 John Parkinson © 2 THE AURORA The Aurora Borealis, the Northern Lights and the Aurora Australis, the Southern lights are phenomena resulting from the

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N S

I

B

F

F = B I lWhere l = length of conductor in the field

Page 17: 1 John Parkinson © 2 THE AURORA The Aurora Borealis, the Northern Lights and the Aurora Australis, the Southern lights are phenomena resulting from the

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S N

HAIR SPRINGS CONTROL MOVEMENT AND ALLOW CURRENT TO ENTER AND LEAVE THE COIL

RADIAL SOFT IRON POLE PIECES

COIL

PERMANENT MAGNET

MOVING COIL

METER

SOFT IRON CYLINDER

Page 18: 1 John Parkinson © 2 THE AURORA The Aurora Borealis, the Northern Lights and the Aurora Australis, the Southern lights are phenomena resulting from the

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S N+

+

Page 19: 1 John Parkinson © 2 THE AURORA The Aurora Borealis, the Northern Lights and the Aurora Australis, the Southern lights are phenomena resulting from the

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N

A

B

D

C

I

S

brushes

EVERY TIME THE COIL PASSES THROUGH THE VERTICAL POSITION, THE COMMUTATOR REVERSES THE CURENT IN THE COIL, IN ORDER TO

SUSTAIN THE ROTATION

DC MOTORC

A

B

SN

D

I

Split ring commutator

Page 20: 1 John Parkinson © 2 THE AURORA The Aurora Borealis, the Northern Lights and the Aurora Australis, the Southern lights are phenomena resulting from the

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LOUDSPEAKER

N

S

N

Solenoid on paper cone is forced to vibrate - left hand rule

magnet

S

N

N N

N

magnet

AC signalcoil

Page 21: 1 John Parkinson © 2 THE AURORA The Aurora Borealis, the Northern Lights and the Aurora Australis, the Southern lights are phenomena resulting from the

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Page 22: 1 John Parkinson © 2 THE AURORA The Aurora Borealis, the Northern Lights and the Aurora Australis, the Southern lights are phenomena resulting from the

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Force experienced by a charged particle (charge Q) moving with a velocity, v in a magnetic field of Flux density, B

+Q

B

I

A

B

l

Particle travels l metres from A to B in t seconds

F

F = B I l

t

QI

t

BQlF

but vt

l

F = B Q v

Page 23: 1 John Parkinson © 2 THE AURORA The Aurora Borealis, the Northern Lights and the Aurora Australis, the Southern lights are phenomena resulting from the

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+ I

FF THE FORCE IS ALWAYS

PERPENDICULAR TO THE MOTION

THE PARTICLE MUST MOVE

ALONG AN ARC OF A CIRCLE

r

mvBQv

2

BQ

mvrarcofradius ,

+

Page 24: 1 John Parkinson © 2 THE AURORA The Aurora Borealis, the Northern Lights and the Aurora Australis, the Southern lights are phenomena resulting from the

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Frequency of Rotation, f

x x x x x x x x x x x xx x x x x x x x x x x xx x x x x x x x x x x x

x x x x x x x x x x x x x x x x x x x x x x x x

B inwards

+

r

mvBQv

2

rfT

rv

22

r

mvBQ

r

frmBQ

2

m

BQf

2

The frequency is independent of the radius and the velocity

This is the principle of the CYCLOTRON

Page 25: 1 John Parkinson © 2 THE AURORA The Aurora Borealis, the Northern Lights and the Aurora Australis, the Southern lights are phenomena resulting from the

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High frequency square wave to accelerate charge across the gap

CYCLOTRON

+High frequency square wavem

BQf

2