WELSH JOINT EDUCATION COMMITTEE Subsidiary... · Web viewWELSH JOINT EDUCATION COMMITTEE CYD-BWYLLGOR ADDYSG CYMRU General Certificate of Education Tystysgrif Addysg Gyffredinol Advanced

WELSH JOINT EDUCATION COMMITTEECYD-BWYLLGOR ADDYSG CYMRU

General Certificate of Education Tystysgrif Addysg GyffredinolAdvanced Subsidiary/Advanced Uwch Gyfrannol/Uwch

MARKING SCHEMES

SUMMER 2002

PHYSICS

INTRODUCTION

The marking schemes which follow were those used by the WJEC for the summer 2002 examination in GCE PHYSICS. They were finalised after detailed discussion at examiners' conferences by all the examiners involved in the assessment. The conferences were held shortly after the papers were taken so that reference could be made to the full range of candidates' responses, with photocopied scripts forming the basis of discussion. The aim of the conferences was to ensure that the marking schemes were interpreted and applied in the same way by all examiners.

It is hoped that this information will be of assistance to centres but it is recognised at the same time that, without the benefit of participation in the examiners' conferences, teachers may have different views on certain matters of detail or interpretation.

The WJEC regrets that it cannot enter into any discussion or correspondence about these marking schemes.

CONTENTSUnit page

PH1 2

PH2 7

PH3 12

PH4 17

PH5 22

PH6 written paper 28

PH6 investigatory task 33

1

PH1 Mark Scheme – May 2002

Notes: This marking scheme, whilst reasonably complete does not give all the answers which were credited by the examiners. It is hoped that the scheme is self-explanatory, though it will need to be read alongside the question paper. The following clarifications may be of use:Statements in brackets [ ] are exemplification, alternatives or statements which, whilst desirable in an answer were not required on this occasion for full marks.The numbers in parentheses ( ) are the marks, usually 1, for each response.e.c.f. stands for error carried forward, and indicates that the results of a previous (incorrect) calculation will be treated as correct for the current section. i.e. the mistake will only be penalised once.The expression “or by implication” indicates that the mark is credited when subsequent credit-worthy working demonstrates that this idea/equation has been used.Incorrect or absent units only attract a penalty when ((unit)) appears, otherwise they are there in the mark scheme for completeness. No penalties for excessive significant figures are applied in this paper.

Question1 (a)

(b)

(i)

(ii)

Any 4 points from concrete brittle or weak under tension top surface [put] under tension stress concentrations occur [at cracks in] top surface [pre-existing] surface imperfections in top surface cracks lengthen / propagate downwards or bonds break[penalise only once for top/bottom confusion]4 1 mark

Steel (1) because not brittle (1) or other correct material and reason. e.g. pre-stressed concrete, because always under compression.

[or by implication]

[or equiv. or by implication]

stress = 6.0 107 N m-2 [or Pa] (1) ((unit))[e.c.f. if numerical error in strain]Assume copper still in Hookean [accept: elastic] region (1) [or uniform cross-section or uniform extension]

4

2

4[10]

2

2 (a)

(b)

(i)

(ii)

(i)

(ii)

(iii)

perpendicular distance

Pmoment of force about P = force perpendicular distance from P to line of action of force [underlined terms (1), credit from diagram] (1)or equivalent statement (with diagram)involving perpendicular component of force.

Pulls of gravity on individual particles behave as a single [vertical] force (1) through a point called the ‘centre of gravity’ (1)[accept answer in special context e.g. toppling.]

F1 passes through A [or by implication] (1)[so] perpendicular distance [in definition] is zero. (1)

c-w moments about A = 20 N 1.2 m + 80 N 1.5 m (1)[ = 144 Nm]

Attempt to equate c-w moments to F2 2.4 m (1)F2 = 60 N (1)

F1 = 40 N (1) e.c.f. from (ii)

2

2

2

3

1[10]

3 (a)

(b)

(c)

5.0 N (1) ((unit))Indicated on diagram (1)

Correctly drawn closed triangle of forces for C, T and 5.0 N (e.c.f from (a)) or parallelogram of forces or by implication if any correct working (1)

Net force = [-] 2.5 N (1) [or by impl.] e.c.f. from (b)

a = (1) [or by impl.] = 4.9 m s-2 (1)

2

5

3[10]

3

4 (a)

(b)

(c)

(i)

(ii)

(i)

(ii)

(i)

(ii)

Ray drawn, glass air, emergent along surface (1)Angle of incidence marked (1)

450 (1)

horizontal reflected ray shown in prism (1)vertical emergent ray shown (1)

ray emerging into water shown (1)bending away from the normal (1)

Partial reflection occurs or a little light does emerge as in (b)(ii) (1)

2

2

1

2

2

1[10]

5 (a)

(b)

(c)

(i)

(ii)

(i)

(ii)

(i)

(ii)

alternating clear and opaque strips (1) [accept etched / scratched lines, slits in a barrier etc.] strips equally spaced or many parallel strips (1)

measuring wavelengths or displaying spectra or showing the wave nature of light.

no: both sides have same dimensions / dimensions of length or units of m [or equivalent] (1)

yes: left hand side dimensionless; r.h.s. has dimensions of length2 or units of m2 [or equivalent] (1)[N.B. If dimensional checks correctly carried out in (i) and (ii), but question not answered, score 1]

by trial and error or otherwise n = 3 (1) [or by impl.] = 730 (1) e.c.f. for

2

1

1

1

3

2[10]

4

6 (a)

(b)

(c)

(d)

(i)

(ii)

(i)

(ii)

(iii)

or change/inc. in vel. per second

or rate of change of vel. [w.r.t. time] (2)[N.B. ‘speed’ instead of ‘velocity’ 1]

(I) anything slowing down [or specific case] (1)(II) anything setting off from rest / at rest while reversing

direction [or specific case] (1)(III) a body moving [at a constant speed] in [an arc of] a

circle / with changing direction (1)

clear attempt to find slope (1)9.8 ms-2 [accept 9.5 – 10.1] emerging clearly from working (1)

(I) distance = area under graph [or ] (1) [or by implication]

[or equiv.]

(II) distance = triangle area (1) [or by implication]= 11.0[0.3] m (1)

2.3 s (1)Displacements 0.7 s – 1.5 s and 1.5 s – 2.3 s are equal and opposite or symmetry about highest point or equivalent. (1)

On the axes: Height scale (no unit penalty) and points correctly plotted for 0.7 s and 2.3 s (1) and 1.5 s (1) [1 mark lost for each error or omission]Curve (1), going to zero at 0 s and 3 s (1)

Line parallel to previous but half the velocity intercept (1)Line terminates at 1.5 s (1)

2

1

1

1

2

3

2

2

4

2[20]

5

7 (a)

(b)

(c)

(i)

(ii)

(i)

(ii)

(iii)

(iv)

(v)

(vi)

(i)

(ii)

direction of propagation or travel or energy flow (1) [accept direction of movement of wave] and direction of particle motion or oscillation or displacement (1)

oscillation direction confined to one direction [in space, perpendicular to propagation direction] (1)

10.0 and 5.0 (1)Intensity amplitude2 [or equiv. or by implication] (1)

Intensity ratio 4 (1) [accept , 0.25] e.c.f.

Any correctly marked C and D (1)

Waves spread / diffract at slits [or equiv.] (1) region of overlap / interference (1)

waves travel different distances / paths to get from slits to given point [except O] (1)

If paths differ by waves arrive in antiphase (1)

destructive interference in such places [or equivalent] (1)

Diagram with source facing plate (1)Standing wave region (between source and plate) shown (1)

[Nodal separation =] 0.006 m (1) e.c.f. [accept ]

2

1

3

1

2

3

3

2

2

1[20]

6


Notes: This marking scheme, whilst reasonably complete does not give all the answers which were credited by the examiners. It is hoped that the scheme is self-explanatory, though it will need to be read alongside the question paper. The following clarifications may be of use:Statements in brackets [ ] are exemplification, alternatives, indications of acceptable range of numerical answers (with ), or statements which, whilst desirable in an answer were not required on this occasion for full marks. The numbers in parentheses ( ) are the marks, usually 1, for each response.e.c.f. stands for error carried forward, and indicates that the results of a previous (incorrect) calculation will be treated as correct for the current section. i.e. the mistake will only be penalised once.The expression “or by implication” indicates that the mark is credited when subsequent credit-worthy working demonstrates that this idea/equation has been used.Incorrect or absent units only attract a penalty when ((unit)) appears, otherwise they are there in the mark scheme for completeness. No penalties for excessive significant figures are applied in this paper.

Question1 (a)

(b)

(i)

(ii)

0.5 A (1)

12.0 V (1)

3.0 V (1)

20 C (1) ((unit))

9.0 V 20 C [e.c.f.] (1) [or Vit or equiv., or by implication] = 180 J (1)

[or attempt to treat as 24 (e.c.f.) in parallel with 6 (e.c.f.)]= 4.8 (1)

1

1

1

1

2

2

2

[10]

7

2 (a)

(b)

(c) (i)

(ii)

(iii)

V = IR (1) [or by impl.] = 1.3 V (1) e.c.f.

number of [free] electrons[charge carriers] per unit vol.[m3] (1)accept: [free]electron density or [free] electron concentration

Each atom contributes only some of its electrons to the free electron sea [or equiv.] (1)

3

2

1

3

1[10]

3 (a)

(b)

(c) (i)

(ii)

[Drift] velocity [or current] reduced [for a given p.d.] (1)[because] collisions between free electrons and ions [accept atoms] more [frequent] (1)[because] ions vibrate [randomly] with greater amplitude [or more vigour etc.] (1) [accept: [because] free electrons have greater random velocity]

(I) I = 0.025 A (1) V = 3.0 V (1)

(II) I = 0.021 A (1) [accept 6.0 V / 292 ] e.c.f. on R from (b)V = 3.5 V e.c.f. on I

either: no, because V 0 when = 0or: no, because V and are not linearly related. (1)

3

2

2

2

1

[10]

8

4 (a)

(b)

(c)

(i)(ii)

(i)

(ii)

(i)

(ii)

ultraviolet [accept u-v] (1)gamma (1)

high speed [or accelerated, or high energy] electrons (1)[or electrons from an electron gun or electrons ‘fired’ or electrons decelerating when they] hit a target (1) [accept material]

120 kV e (1) [or by impl.]= 1.9 10-14 J (1)

No change [ to min] (1)[because] min photon energy = energy of incident electron (1)[accept: min depends [only] on incident electron’s energy]

Changes occur [to wavelengths of the spikes] (1)Spikes’ wavelengths determined by [energy levels in] atoms of the target (1).

11

2

2

2

2[10]

5 (a)

(b)

(c)

(i)

(ii)

Any two (1+1)from particular wavelengths are absorbed atoms[‘ electrons] are raised to higher energy levels light re-radiated in all directions

Clear evidence of use of E = hf (1), (1)

Differences in energy levels considered [or by impl.] (1)3.0 10-19 J transition identified [on diagram] (1)4.7 10-19 J transition identified [on diagram] (1)Atoms likely to be calcium [only] (1) [N.B. both transitions must identified for last mark]

2

2

2

4

[10]

9

6 (a)

(b)

(c)

(i)

(i)

(ii)

(iii)

(i)

(ii)

(iii)

Nuclear waste is radioactive (1) and has long half-life [or needs long term storage or can cause named health problem] (1) Coal-burning waste - any two valid points from is largely discharged into atmosphere causes global warming causes acid rain causes respiratory disease (21)

energy = power time (1) [or by impl.]= 7.2 MJ (1) ((unit)) [accept 2.0 kWh]

power = IV (1) [or by impl.]I = 8.7 A (1)

(I) 9 [accept 9.09, 9.1, 10] (1)(II) either: Yes, because readers might not realise they only

get the heat they pay for or: No because the 220 W tells readers that the heater

doesn’t give out much heat – or other well-argued response

[accept valid criticism of quotation in question stem] (1)

(I) 1.5 joules per coulomb (1) of [electrical energy or ability to do work in circuit] is given to the charge passing through cell (1)

(II) Find intercept (1) [or equivalent]

VPQ = 0.9 V (1) [or by implication] (1)[]Vr [or ‘lost volts’] = 0.6 V (1)[] r = 0.3 . (1)[N.B. Give 1 mark if r found without using the I =0.2 A case]

(I) 5.0 A (1)(II) 0 [N.B. no e.c.f. from (I)](III) No pd. in external circuit [or equiv. e.g. R = 0] (1)

4

2

2

1

1

2

1

3

11

2[20]

10

7 (a)

(b)

(c)

(i)

(ii)

(i)

(ii)

(iii)

(iv)

(i)

(ii)

(iii)

[Isotopes are] atoms [or nuclei] of the same element [or with same atomic number / proton number / number of protons] (1) [but] with different number of neutrons / nucleon numbers / mass numbers (1)

55 (1)no. of electrons = no. of protons [or atom is neutral] (1)

Some electrons reach [or are attracted to] collecting electrode (1) because of positive potential [or positive charge on] collecting electrode (1)Electrons are returned to the caesium [via power supply] (1)

I = e number of electrons flowing per second [or by impl.] (1)number = 1.3 1010 s-1 (1)

reverse supply connections

increase pd. until current [just] drops to zero (1)Voltmeter reading gives Ek max in eV [or e voltmeter reading gives Ek max] (1)

correct straight line drawn (1)

4.4[0.1] 1014 Hz (1)

Any 3 from w.f. is [minimum] energy electrons need to escape metal [or

this definition implied] photon energy must be at least as large as this all energy to release an electron comes from one photon photon energy frequency [so below frequency for which

hf = w.f., photon does not have enough energy] (31)

2

2

3

2

1

2

4

1

3

[20]

11


Notes: This marking scheme, whilst reasonably complete does not give all the responses which were credited by the examiners. It is hoped that the scheme is self-explanatory, though it will need to be read alongside the question paper. The following clarifications may be of use:

Statements in brackets [ ] are exemplification, alternatives, indications of acceptable range of numerical answers (with ), or statements which, whilst desirable in an answer were not required on this occasion for full marks.

The numbers in parentheses ( ) are the marks, usually 1, for each response.

By the nature of a practical examination, the data are the candidates own and every attempt is made not to penalise candidates unduly for poor results, especially in the sections involving their analysis. The various sections of the questions are independent. e.c.f. stands for error carried forward, and indicates that the results of previous (incorrect) calculation or poor measurement will be treated as correct for the current section, i.e. the mistake will only be penalised once. This does not extend to errors of principle, for example inappropriately drawing a best-fit line through the origin and subsequently stating that the intercept is zero.

12

TEST 1 – SESSIONS 1 & 2

Question Answers / Explanatory notes Marks available

1 (a)

(b)

(c)

(d)

(i)

(ii)

(i)

(ii)

(iii)

Readings correctly recorded and repeated (1)Uncertainty correctly calculated [allow one more decimal place than instrument resolution](1)

Statement withaverage/mean value quoted (1)uncertainty or % uncertainty quoted (1)

Tabulation: h, d and d2 tabulated and columns labelled (1) units quoted in all headings eg. cm, cm2 [or (d/cm)2] (1)

Readings: sensible intervals (1) 4 readings & range of at least 20 cm (1) mean value of d calculated (1) calculated (1)

Graph axes drawn, correctly oriented, labelled with units (1)

[unit penalty only applied once in (b) and (c)] scales – non-awkward, correct with respect to the data,

graph occupying at least half the paper (1) points – 4 correct – e.c.f. from 2nd bullet point (1) line of best fit (1) e.c.f.

comment that:straight line (1), through the origin (1)or show that if h is doubled, so is d2, or show that k is a constant (2)[attempt to compare two pairs of results (1)]

unit: m or cm (1)using graph: good size triangle (1),

value of gradient correctly calculated (1)

height of bench (1)

2

2

6

4

2

3

1

[20]

13


2 (a)

(b)

(c)

(d)

(i)

(ii)

(i)

(ii)

Table of results with headings: distance & tension [or symbols] and units (1) sensible intervals and at least 60 cm range (1) at least 5 pairs of readings (1) all readings repeated at least once (1) mean to sensible no. of s.f. consistent with repeated

readings (1)

Graph axes fully labelled (with units) (1) non-awkward scales, graph occupying half of paper

(1) 4 correctly plotted points (2) [2 points (1)] line of best fit consistent with results (1)

graph extrapolated to T axis (1)correct reading of intercept (1)

to determine the gradient use of good sized triangle (1) using the correct ratio and values (1) value calculated to 2 or 3 s.f. with unit (N cm-1) (1)

derivation equal moments stated [or implied] (1) correct statement of equation with clockwise and anti-

clockwise moments (1) correct manipulation to derive the required equation (1)

straight line (1)intercept on T (y) axis (1)[or equivalent working by substitution or comparing gradient and intercepts with theoretical values]

5

5

2

3

3

2

[20]

14


3 (a)

(b)

(c)

(i)

(ii)

(i)

(ii)

(iii)

Circuit diagramAll 5 symbols correctly positioned [ignore supply polarity] (2)[-1 for each incorrect symbol or position]

Tabulation headings (1) and units (1) as instructed 7 correct lines (7 1) -1 for inconsistency in raw data [indicate C] -1 for inconsistency in calculated values of R [indicate S]

Graph axes labelled with units [e.g. R/ or R in or R ()] (1) suitable scales (1) all points plotted (2), [4 points plotted (1)] e.c.f. line (curve!) of best fit (1) e.c.f.

Iw recorded, with unit, in range 0.15 – 0.20 A (1)

Rw recorded, with unit, from graph. (1)N.B. Maximum unit penalty for (i) and (ii) = 1

Resistivity determinationcorrect substitution into equation (1)correct order of magnitude answer with unit (1)

2

9

5

1

2

2

[20]

15

TEST 2 – SESSIONS 3 & 4 – as test 1 except:


2 (a)

(b)

(c)

(d)

(i)

(ii)

(i)

(ii)

Table of results with headings: distance & tension [or symbols] and units (1) sensible intervals and at least 70 cm range (1) at least 5 pairs of readings (1) all readings repeated at least once (1) mean to sensible no. of s.f. consistent with repeated

readings (1)

Graph axes fully labelled (with units) (1) non-awkward scales, graph occupying half of paper

(1) 4 correctly plotted points (2) [2 points (1)] line of best fit consistent with results (1)

graph extrapolated to T axis (1)correct reading of intercept (1)

to determine the gradient use of good sized triangle (1) using the correct ratio and values (1) value calculated to 2 or 3 s.f. with unit (N cm-1) (1)

analysisvalue of A, from (c)(ii), correctly substituted into the equation

(1)value of B, from (c)(i), correctly substituted into the equation

(1)

derivation equal moments stated [or implied] (1) correct statement of equation with clockwise and anti-

clockwise moments (1) correct manipulation to derive the required equation (1)

5

5

2

3

2

3

[20]

16

PH4 Mark Scheme – June 2002



1 (a)

(b) (i)

(ii)

(iii)

2

4

2

2

[10]

17

2 (a)

(b)

(c)

heat from wire = power time [or by impl.] (1)

= 50 MJ (1)

escaped heat = 12 or 13 MJ (1) e.c.f.

[e.c.f. if slip]

3

3

4

[10]

3 (a)

(b) (i)

(ii)

(iii)

On the upswings KE is converted to PE (1)on the downswings [gravitational] PE is converted to KE (1)Total energy remains constant [or statement of Princ.] (1)[Full credit for correct answers including ‘losses’]

damped (1)

Pendulum bob (or paper) hits air molecules [or correct reference to air resistance] (1)Air molecules’ speeds / KE increase [slightly on average] (1)+ any one of: energy lost from system to surroundings internal/random/thermal energy of molecules

[in bob/paper as well as air] increases temperature [of air and bob] increases (1)

3

1

3

3

[10]

18

4 (a)

(b)

(c)

(d)

(e)

graph slope constant [or acceleration displacement](1)graph slope negative [or acceleration in opposite direction from displacement] (1)[Definition of s.h.m. alone scores first mark only]

0.050 m (1)

F = ma correctly used (1)k = 8 N m-1 ((unit)) (1)

2 = 40 s-2 [or by impl.] (1) e.c.f. from (c)T = 0.99 s (1)

Either

or

2

1

2

2

3[10]

5 (a)

(b)

(c)

(i)

(ii)

[body’s] mass [body’s] velocity (1)

A body’s rate of change of momentum is proportional [accept equal] to the [net] force applied [accept F=(mv-mu)/t] (1) and is in the direction of the force (1)

attempt to draw tangent at 5.0 s (1)attempt to find tangent slope (1)answer in range 800 N – 1200 N (1)[one mark for calculating average force over first 5 seconds – accept between 1600 N and 1800 N]

Principle of conservation of momentum referred to, or a recognisable attempt made to apply it. (1)12000 [+ 0] = 4000 + 600v [or equiv. or by impl.] (1)B’s speed after collision = 13 m s-1 (1)Assume negligible external forces [or A and B move in a straight line] (1)

1

2

3

4

[10]

19

6 (a)

(b)

(c)

(i)

(ii)

(i)

(ii)

(iii)

(iv)

(v)

Any two from collisions occur collisions elastic [on average] molecules move in straight lines between collisions no favoured direction range of molecular speeds motion random

Gas is largely empty space or separations between molecules large [or reduced] or molecules occupy neg. fraction of vol. (1)

Pressure is caused by molecules hitting walls [or by impl.] (1)Any given area (1) of wall is hit more frequently (1) [accept: at an increased rate]

attempt to apply pV = nRT to a point (1)yielding T = 290 K (1)application of pV = nRT to another point yielding T = 290 K (1)[or pV product, 120 J, checked at 2 or more points]

(I) Work done = area under graph (1) [or by impl.]= trapezium area [or triangle + rectangle] (1)= 225[5] J (1)

(II) too high, because curve lied below straight line (1)

First law of thermodynamics stated [or implied] (1)No change in internal energy [N.B.explicit statement needed] (1)Heat must flow in to supply work done by gas (1)

2

1

3

3

2

2

3

1

3

[20]

20

7 (a)

(b)

(i)

(ii)

(i)

(ii)

(iii)

(iv)

approx. sinusoidal graph drawn (1)at least one and at most five cycles, occupying at least ¼ of vertical space and half-cycles of equal time (1)

(I) relevant vertical distance marked or described (1)multiply by V cm-1 or V div-1 from calibration (1)

(II) horizontal distance for 1 cycle or stated number of cycles shown or described (1)multiplication by ms cm-1 or ms div-1 etc. (1) [N.B. no second point penalty if 2nd mark lost in (I) for loose formulation]

application of or (1)

[Vr.m.s. = 65.97 V is indicative of correct procedure]

900 or (1)the p.d. (1)

[for VL accept 66 V or 66 V] VL (1) [for VR accept 88 V or 88 V]

VR [accept other orientation / reflection]

VR = 88 V (1) [accept 88 V] (1)

[If appears wrongly in final answer, only last mark is lost]

(I)

(II) P = 0 (1)

2

2

3

3

2

2

4

1

2

1

[20]

21

PH5 Mark Scheme – June 2002



1 (a)

(b)

(c)

(d)

(i)

(ii)

8 (1)

8 (1)

Mass of nucleons [= 8(1.007 + 1.009)] = 16.128 u [or by impl] (1)mass defect = 16.128 – 15.995 = 0.133 u [or by impl] (1)

binding energy per nucleon =

Energy released = 3.77 1025 16 7.76 106 1.6 10-

19 = 7.49 1014 J (1)

[or equivalent alternative solution e.g. based upon fractional mass loss (2)]

1

1

3

3

2

[10]

22

2 (a)

(b)

(c)

gravitational force on a mass at Earth’s surface is its weight mg [or equiv.] (1)

Either

or

[or equiv.]

2

2

4

2

[10]

23

3 (a)

(b)

(i)

(ii)

(iii)

(i)

(ii)

[or r = 105/0.222 = 4.5105 moles (1) N0= rNA= 2.711019(1)]

[or equivalent working using 2-n ,n = no. of half lives]

% change =

2

2

2

3

1

[10]

4 (a)

(b)

(i)

(ii)

magnetic flux [through the ring] increases (1)[so] e.m.f. induced [by Faraday’s Law] (1) and hence current.

Current indicated anti-clockwise viewed from magnet (1)Induced current opposes the change [or “Lenz’s law”, or r.h. rule] (1)[N.B. For (i) and (ii) together, credit answers in terms of the Lorentz force on moving charges in the loop as follows:

velocity of a charge at top of loop is to the left (1)direction of B is [roughly] N.E. [or equivalent] (1)FB [on +q] is into the paper [by Fleming l.h. rule] (1)Moving charges constitute a current. (1)Current a.c.w. viewed from left (1) Max mark 4]

p.d. axis labelled with unit (1)p.d. axis scale (1)

For 0<t<4 s : or on graph (1)

For 4<t<8 s V = 0: [or on graph] (1)

For 8<t<10 s V = : or on graph (1)

2

2

6

24

[10]5 (a)

(b)

(c)

(i)

(ii)

Direction is that of the resultant field [or by impl.] (1), which is horizontal to the right. (1)

[or implied] (1)

E1

E2 E

[mark is for clear

evidence of attempt to compound the intensities]

2

2

2

4

[10]

25

6 (a)

(b)

(c)

(d)

(e)

(f)

(g)

(i)

(ii) VPQ = [RI = 2.35 103 0.03 =] 70.5 V (1) e.c.f.

P = I2R (1) = [2.35 103 0.032 =] 2.12 W (1) e.c.f.

I = nAev (1)correct area calculation (10-3 10 10-3) (1)

FB = Bev (1) [or by implication] [= 2.5 1.6 10-19 7.5 10-4 ] = 3.0 10-22 N (1) e.c.f.vertically upwards (1)

[or VH= BI/tnq (1) = 18.8 V (1)]

force on electrons is towards Y (1) top face (Y) is negatively charged [e.c.f.] (1)X is at higher potential [e.c.f.] (1)

[positive] carriers now moving to right FB is [still] upwards (1) e.c.f.top face (Y) is at higher potential (1) e.c.f.

3

1

2

4

3

2

3

2

[20]

26

7 (a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

(i)

(ii)

alternating p.d. applied between them [or equiv.] (1)for accelerating the particles (1)

(I) field indicated into the diagram e.g. (1)(II) anti-clockwise spiral indicated on diagram (1)

Cyclotron: B is constant and r varies (1)Synchrotron: B varies and r is constant (1)

Energy transfer required = [20 – 5 =] 15 MeV [or by impl.] (1)Energy transfer with each traverse of gap = 10 keV (1)[because 2 traverses per circuit] number of circuits required

Mass defect [= 8.023 – 8.004] = 0.019 u [or by impl.] (1) Energy equivalent [= 0.019 934 106] = 17.7 MeV (1)[Total energy available = 17.7 + 20.0 = 37.7 MeV]Energy per particle = 18.9 MeV (1)

most s undeviated [or or equivalent][showing that] the nucleus is small [or equivalent] (21)

2

11

2

2

2

3

2

3

2

[20]

27

PH6 – Synoptic Paper – Mark Scheme – June 2002

Notes: This marking scheme, whilst reasonably complete does not give all the answers which were credited by the examiners. It is hoped that the scheme is self-explanatory, though it will need to be read alongside the question paper. The following clarifications may be of use:Statements in brackets [ ] are exemplification, alternatives, indications of acceptable range of numerical answers (with ), or statements which, whilst desirable in an answer were not required on this occasion for full marks. The numbers in parentheses ( ) are the marks, usually 1, for each response.e.c.f. stands for error carried forward, and indicates that the results of a previous (incorrect) calculation will be treated as correct for the current section. i.e. the mistake will only be penalised once.The expression “or by implication” indicates that the mark is credited when subsequent credit-worthy working demonstrates that this idea/equation has been used.Incorrect or absent units only attract a penalty when ((unit)) appears, otherwise they are there in the mark scheme for completeness. Significant figures may be examined in questions requiring data analysis.


1 (a)

(b)

(c)

(i)

(ii)

(iii)

(i)

(ii)

(iii)

(iv)

reference to etc. (1)implying shape consistent (1)[or two valid points from graph same capacitance (2)][“reactance decreases with frequency” (1)]

use of sensible point e.g. 4 and 20 Hz (1)

use of to give 2000 F (1)

0.024 C (1)

0.144 J (1)

0.00024 s ((unit)) (1)

Reference to internal resistance limiting current / dissipating power/energy or having a p.d. across it (1)

2

1

2

1

1

1

1

1[10]

28

2 (a)

(b)

(c)

[accept illogical working eg. 210/220 = 4.5%]

leading to d = 220 m (no more than 3 s.f.) (1)

[working leading to] 0.2% [accept 0.18%] (1)[accept working combining the uncertainties is m and l.]

Use of

leading to A = 3.8 10-8 m2 [or by implication] (1)d ~ 220 m (no more than 3 s.f.) (1)

leading to 1% [accept more s.f.] (1)

method 2 (1) e.c.f.

1

3

1

3

1

1

2

1

2

[15]

29

3 (a)

(b)

(i)

(ii)

(iii)

(iv)

(i)

(ii)

(iii)

(iv)

(v)

(vi)

Force is downwards on the scales [since positive reading] (1)by Newton’s 3rd law [upwards on wire] (1)

right-hand pole labelled N

[Fleming’s] left hand rule (1)

the forces are horizontal or the forces cancel (1)

F = BIl[sin] (1)

F l (1)

On the graph axes labelled with units (1) all points correctly plotted (2) [4 points correct (1)] line of best fit (1)

Best fit line is straight (1) and through the origin (1) [or graph is of the type y = mx].[straight] line is close to all 4 points (1)“close” is specified i.e. within error limits (1)

gradient = BI [or implied] (1)sensible attempt to determine gradient [= 2.875 10-1 N m-1]B = 1.44 [0.06] T ((unit)) (1) [accept N m-1 A-1, Wb m-2]

wire outside central region of magnetic field (1)magnetic field not constant (1)[outside strong region of field implies both marks]

2

1

1

1

1

1

4

4

3

2

[20]

30

4 (a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

(i)

(j)

the desired equations werekinetic + nuclear heat/thermal + lightkinetic + chemical heat/thermal + lightl-h sides all 3 energies (2), 1 or 2 correct (1)r-h sides “heat/thermal + other” (2)

mass of 1 mole = 238 g / 0.238 kg (1)

number of moles =

number of atoms = 2.5 1024 (1)

use of A = N (1) [leading to 12.3 MBq]

power = energy of -particle number per second [or by implication] (1)

= 4.19 10 6 1.6 10 -19 12.3 106 (1)[mark is for 106 and 1.6 10-19 conversions]

Colonel Daxon because 8 W of nuclear power/energy too low (1)

people in [struck] vehicles and who entered [struck] vehicles encountered a higher concentration / dosage [of DU] (1)[For people with close contact] -particles will not be absorbed by the air / will reach the skin. (1)

any two good points relating to a comparison (2 1)eg. particles absorbed by to mm of soil DU dust on surface can be blown into the atmosphere DU half as radioactive as natural uranium cultivation (etc.) will turn up the top layers of soil

concentration per cm2 = [or equivalent] (1)

activity = 0.6 Bq (1)[N.B. Use of 105 rather than squaring allowed for 1 mark]

similar to background [accept slightly more/less, same as](1) e.c.f. from (i)

4

3

3

1

2

1

2

2

2

1

31

(k)

(l)

(m)

(n)

time taken for half [the uranium] (1) to be eliminated [or equiv.] from the body (1)[accept for 1 mark – half uranium disintegrated]

exponential (1) decrease / decay (1)[or every twelve hours (1) the uranium halves (1)]

[insoluble UO2] stays in the body longer (1)the body receives a higher dose or it has more chance to injure the body etc. (1)

a ratio > 137.8 means that U235 has been removed (1)U235 is removed to produce DU (1)higher ratio cannot come from natural sources (1)

[or equivalent statements]

2

2

2

3

[30]

N.B. The PH6 Investigatory Task component is marked according to the scheme in the subject specification. For comments about interpretation, please refer to the examiner’s report.

32

Mark scheme for the assessment of the Investigatory Task (PH6 02)

Assessments will be made by the Board under the five assessment headings listed below. Each of the ability/skill areas 1-15 will carry a range of marks 0-3. These marks will be allocated within mark schemes using the following broad scale:

0 - will only be awarded if a candidate fails to demonstrate any achievement in that ability/skill being tested.

1 - some attempt has been made to satisfy the required parameters.2 - there is clear evidence that the candidate has demonstrated the particular ability/skill.

3 - the candidate has demonstrated a high level of ability/skill and has communicated this effectively within the coursework.

A. Planning the investigation (9 marks)Candidates should have:

(1) considered methods appropriate to an investigation at a full A level standard.(2) correctly identified the variables likely to feature within the investigation.(3) planned an effective strategy for answering the problem.

B. Implementing the experimental work (9 marks)Candidates should have:(4) adopted effective techniques and safe working procedures.(5) selected appropriate instruments and procedures to give the accuracy

required.(6) demonstrated that they have followed their outline plan and built in

modifications in the light of results, if appropriate.

C. Recording and collecting data (9 marks)Candidates should have:(7) made and recorded, in table format, sufficient relevant observations and

measurements to the appropriate degree of precision.(8) displayed the units, instrument resolutions and zero errors.(9) evidenced ability to present graphs accurately in terms of labelling, scales,

units and error bars.

D. Analysis and evaluation (9 marks)Candidates should have:(10) used data appropriately to analyse the identified problem(s).(11) expressed an awareness of the limitations of experimental measurements by

quoting any result to an appropriate number of significant figures.(12) critically analysed the experimental procedure and the reliability of the data

collected; evaluated the techniques used, and suggested improvements where appropriate.

E. Communication (9 marks)Candidates should have:(13) presented a valid conclusion which provides an appropriate response to the

identified problem(s).(14) presented a well-structured and concise report employing a range of

vocabulary and modes of presentation.(15) demonstrated reasonable IT skills.

N.B.Skill areas A2, B4, B6 and E15 are assessed internally and moderated by the board.

33

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34

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