Page 125 - Physics Form 5 KSSM_Neat

Electromotive force and potential difference have the same S.I. units. However, electromotive CHAPTER 3
force differs from potential difference under different circumstances. Electricity

Activity 3.6

Aim: To compare between e.m.f. and potential difference
KEMENTERIAN PENDIDIKAN MALAYSIA
Apparatus: 1.5 V dry cell, cell holder, switch, bulb, connecting wires and voltmeter
Instructions:
1. Set up the apparatus as shown in Figure 3.23 with the switch S open (open circuit).
V

S

Figure 3.23
2. Observe what happens to the bulb and record the voltmeter reading in Table 3.11.
3. Close the switch S (closed circuit). Observe what happens to the bulb and record the
voltmeter reading.
Results:
Table 3.11

Open circuit Closed circuit

State of the bulb

Voltmeter reading / V

Discussion:
1. What is the change in energy when the bulb lights up?
2. Based on the results of this activity:
(a) which circuit measured the potential difference across the bulb?
(b) what is the quantity of electrical energy released by the bulb for every coulomb of charge
that flows through it?
3. What is the e.m.f. of the dry cell?
4. What is the quantity of electrical energy that is supplied to every coulomb of charge flowing
through the dry cell?
5. What is the difference in voltmeter readings between the open circuit and the closed circuit?
Discuss why this difference occurs.

LS 3.3.1 115