P2.2 Exam Question and Markscheme – 10 marks, 10 minutes
Q1.
Using electric current
(a) The photograph shows a device used to measure the amount of light.
The circuit diagram shows how the components inside this device are connected.
(i) Complete the sentence by putting a cross (
The meter used in this circuit is
) in the box next to your answer.
(1)
A a voltmeter connected in series with the LDR
B a voltmeter connected in parallel with the LDR
C an ammeter connected in series with the LDR
D an ammeter connected in parallel with the LDR
(ii) The amount of light entering the light-dependent resistor (LDR) increases.
Which row of the table correctly describes the change in the resistance of the LDR
and the change in the current in the circuit?
Put a cross ( ) in the box next to your answer.
(1)
%%%
resistance of the LDR
current in circuit
A
increases
decreases
B
increases
increases
C
decreases
decreases
D
decreases
increases
(iii) The device is used as a light meter.
It has a 9 V battery.
Calculate the current when the resistance of the LDR is 600 Ω.
(3)
current = ........................................ A
P2.2 Exam Question and Markscheme – 10 marks, 10 minutes
(iv) When the light meter has been used for a long time, the meter reading becomes
incorrect.
Suggest what has happened.
(2)
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(b) A different light meter has a diode in its circuit.
(i) Explain what happens when the battery is reversed.
(2)
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(ii) Suggest why the manufacturer of the light meter has included a diode.
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Q1.
Answer
Question Number
(a)(i)
C
Question Number
(a)(iii)
Mark
(1)
Answer
Question Number
(a)(ii)
Acceptable
answers
Acceptable
answers
D
Mark
(1)
Answer
substitution (1) 9
= I × 600
transposition (1) I
Acceptable
answers
allow substitution
and transposition
in either order
Mark
(3)
(1)
P2.2 Exam Question and Markscheme – 10 marks, 10 minutes
= 9/600
evaluation (1) =
0.015 (A) OR=15
mA
Question Number
(a)(iv)
Question Number
(b)(i)
Question Number
(b)(ii)
Answer
give full marks for
correct answer,
no working
Acceptable
answers
An explanation
linking the
following
• battery
voltage has
decreased (1)
• (so) less
current (than
expected) (1)
Answer
(2)
Acceptable
answers
An explanation
linking the
following points
• stops working
(1) • (because)
diode will only
conduct in one
direction (1)
Answer
so that the meter
connections are
the correct way
round / eq
Mark
Mark
(2)
Acceptable
answers
will prevent
damage if battery
is (accidentally)
connected the
wrong way round
Mark
(1)