Page 33 - Spotlight A+ Physics Form 4.5

Physics SPM Model Paper

Paper 3
[15 marks]
Instruction: Answer all questions.

1. You are required to carry out an experiment to investigate how resistance of a bulb changes with the potential
difference across it.
d.c. power supply
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©PAN ASIA PUBLICATIONS

Slide wire
Mark 0.0 cm

Meter rule
Crocodile clip
A
Bulb

V
Figure 1.1
SPM MODEL PAPER (i) Turn on the switch.
(a) The circuit has been set up for you. Carry out the following steps below:

(ii) Adjust the position of the crocodile clip on the slide wire until the potential difference across the
bulb is 0.2 V.
(iii) Record the current reading I, indicated by the ammeter.
(iv) Adjust the crocodile clip and record the corresponding value of I for V = 0.8 V, 1.4 V, 2.0 V and
2.6 V.
(v) Turn off the switch.
(vi) Calculate and record the resistance of bulb, R for each value of V in Table 1. Use the equation
V
R = —–.
I
Table 1
V / V I / A R / Ω
0.2
0.8

1.4
2.0
2.6
[6 marks]

(b) Plot the graph of R (Ω) against V (V). [3 marks]
(c) State what the shape of the graph tells you about the relationship of resistance of the bulb filament with
the potential difference across it. [2 marks]
(d) In a similar type of experiment, changes in current and potential difference for the bulb can be achieve
by using a variable resistor instead of a slide wire. Draw the new electrical circuit. [2 marks]
(e) What will happen to the shape of the graph if the bulb is replaced by a semiconductor diode in forward
biased configuration? [2 marks]
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