Page 97 - Physics_Form_2

Current electricity

3. Calculate the resistivity of a wire of
length 2 m and cross-sectional area A
0.004 cm if its resistance is Bulb A(R =2Ω)
2
A
3.0 ohms. 12 V I B
4. When a 6 V battery is connected Bulb A(R =4Ω)
B
FOR ONLINE READING ONLY
to a lamp, a current in the circuit is
measured to be 0.4 A. What is the Figure 2.69
resistance of the lamp?
5. The e.m.f of a cell is 9 V. How Determine the voltage across:
much work is required to move one (i) bulb A.
electron from the negative terminal (ii) bulb B.
to the positive terminal? Ignore the (c) How much current will flow in
internal resistance of the cell. the circuit?
6. A bulb with a resistance of 5 Ω is 8. A 12 V battery is connected to two
connected to an 8 V battery. If the bulbs as shown in Figure 2.70.
internal resistance of the battery is X
neglected: I I I B
(a) How much current will flow A
through the bulb? Bulb A Bulb B
R =2Ω
(b) How much light and heat energy 12 V A R =4Ω
B
does the lamp produce in one I A
hour? I I B
Y
7. (a) Look at the following photo of a Figure 2.70 S
light bulb in Figure 2.68. Label (a) What is the voltage across:
the filament and explain why it
glows. (i) bulb A?
(ii) bulb B?
(b) What is the current flowing
through:

(i) bulb A?
(ii) bulb B?

(c) What is the total current, I?
9. (a) What is the benefit of using a
Figure 2.68 circuit breaker rather than a
fuse?
(b) A 12 V battery is connected (b) An electrician wants to replace a
to two bulbs as shown in faulty fuse with a normal piece
Figure 2.69.

91

Physics Form 2 Final.indd 91 25/10/2025 10:26