Page 15 - 1202 Question Bank Physics Form 5

Reinforcement and Assessment of Science Process Skills
for Paper 3 (Practical Test)

1. In this experiment, you will investigate the relationship between the base current, I with the collector
B
current, I for npn transistor.
C
(a) Set up the apparatus as shown in Diagram 1.

R = 1 kΩ
1
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R = 1 kΩ A
3
2
I
R = 50 kΩ C
2
A 6 V
1
I
B
R = 0 – 1 kΩ
4

Diagram 1
(i) Close the switch and adjust the rheostat until the reading on ammeter A is 10 mA.
1
(ii) Record the reading on ammeter A in the table.
2
(iii) Repeat the above procedure by adjusting the rheostat until the readings on ammeter A are
2
20 mA, 30 mA 40 mA and 50 mA. [6 marks]

I / mA I / mA
B C

(b) State the variables for this experiment;
(i) Manipulated variables [1 mark]
(ii) Responding variable [1 mark]

(c) (i) Plot a graph of collector current, I (y-axis) against base current, I (x-axis).
C B
(ii) Calculate the gradient of the graph. [3 marks]
(d) (i) The equation relating the collector current, I to the base current, I is
C B
I = kI
C B
where k is a constant
Using answer from (c)(ii), calculate the value of the constant k.
(ii) Calculate the magnitude of the collector current, I when the base current, I is 85 mA.
C B
[3 marks]
100 Question 1:
SOS TIP (d) Linearise the equation and establish a relationship with y = mx + c.

Chp 5_1202 QB Physics F5.indd 100 07/01/2022 2:10 PM