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Physic A Level 9702 w 16 Markscheme 52

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® IGCSE is the registered trademark of Cambridge International Examinations.
This document consists of
5
printed pages.
© UCLES 2016
[Turn over
Cambridge International Examinations
Cambridge International Advanced Subsidiary and Advanced Level
PHYSICS 9702/52
Paper 5 Planning, Analysis and Evaluation
October/November 2016
MARK SCHEME Maximum Mark: 30
Published
This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began, which would have considered the acceptability of alternative answers. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October/November 2016 series for most Cambridge IGCSE
®
, Cambridge International A and AS Level components and some Cambridge O Level components.
Page 2 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016
9702 52
© UCLES 2016
Question Answer Marks 1 Defining the problem
p
is the independent variable and
B
is the dependent variable, or vary
p
and measure
B
.
1
Keep the current/
I
(in the electromagnet) constant.
1 Methods of data collection
Labelled diagram showing Hall probe correctly positioned (along
p
) and ruler correctly positioned and either Hall probe or rule supported.
1
Correct circuit diagram to include d.c. power supply in series with coil and ammeter. Must be a workable circuit diagram to measure current through the coil.
1
Measure
p
with ruler.
1
Method to determine an accurate value of
p
. Examples include: Height of P above bench – height of electromagnet Height of P measured from ruler across the top of the electromagnet
1 Method of analysis
Plot a graph of ln
B
against
p
.
1
α
= – gradient
1
I
N k
y
intercept
e
−
=
1
Page 3 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016
9702 52
© UCLES 2016
Question Answer Marks Additional detail including safety considerations
6
1. Keep the number of turns/
N
constant. 2. Use large number of turns/current (to increase
B
). 3. Avoid overheating the coil/do not touch hot coil. 4. Use of variable resistor to keep ammeter reading constant. 5. Method to ensure that Hall probe is equidistant from the poles, e.g. determine centre of electromagnet and use of plumb line/ruler and spirit level/set square. 6. Adjust Hall probe until maximum reading obtained/perpendicular to field. 7. Repeat each experiment for the same value of
p
and reverse the current/Hall probe and average 8. ln
B
= –
α
p
+ ln
kN
I
9. Relationship is valid if the graph is a straight line. 10. Calibrate Hall probe using a known field.
Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016
9702 52
© UCLES 2016
Question Answer Marks2 (a)
gradient =
q y
-intercept = lg
p
1 (b)
2.80 or 2.799 or 2.7993 0.28 or 0.279 2.79 or 2.792 or 2.7924 0.30 or 0.301 2.77 or 2.771 or 2.7709 0.36 or 0.362 2.72 or 2.716 or 2.7160 0.49 or 0.491 2.69 or 2.690 or 2.6902 0.57 or 0.568 2.67 or 2.672 or 2.6721 0.61 or 0.613 All first column correct – either 2 and 3 decimal places or 3 and 4 decimal places. All second column correct. Allow a mixture of decimal places. Uncertainties in lg (
V
/
V) from
±
0.02 to
±
0.01. Allow more than one significant figure.
1 1 1 (c) (i)
Six points plotted correctly. Must be within half a small square. No “blobs”.
1
All error bars in lg (
V
/
V)
plotted correctly. All error bars to be plotted. Total length of bar must be accurate to less than half a small square and symmetrical.
1 (ii)
Line of best fit drawn. Line must not be drawn from top point to bottom point unless points are balanced. Upper end of line should pass between (2.694, 0.55) and (2.700, 0.55)
and
lower end of line should pass between (2.770, 0.35) and (2.776, 0.35).
1
Worst acceptable line drawn correctly. Steepest or shallowest possible line that passes through all the error bars. Mark scored only if all error bars are plotted.
1 (iii)
Gradient determined with a triangle that is at least half the length of the drawn line. Read-offs must be accurate to half a small square. Gradient must be negative.
1 Method
of determining absolute uncertainty. uncertainty = gradient of line of best fit – gradient of worst acceptable line
or
uncertainty = ½(steepest worst line gradient – shallowest worst line gradient)
1

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