Page 129 - Physics Form 5 KSSM_Neat

When a graph of V against I is plotted, a straight-line graph CHAPTER 3
SCAN ME
with a negative gradient is obtained as shown in Figure 3.28. SCAN ME
A comparison of
shapes of graphs Electricity
V / V
The equation for the linear of V against I in
graph is: the experiment
Ɛ to determine
the e.m.f. of a
KEMENTERIAN PENDIDIKAN MALAYSIA
Gradient = –r y = m x + c
dry cell and the
V = –r I + Ԑ experiment to
verify Ohm's Law
Intercept at vertical axis, c = Ԑ https://bit.ly/3loBfMY
0 I / A Gradient, m = –r
Figure 3.28 Graph of V against I

Activity 3.8

Aim: To study the effects of connecting dry cell in series and parallel arrangements on:
• e.m.f., Ԑ
• potential difference, V
• internal resistance, r
• current flows in the circuit
Apparatus: Six 1.5 V dry cells, cell holder, switch, connecting wires, ammeter, voltmeter and
10 W resistor
Instructions:
1. Set up the apparatus as shown in Figure 3.29 for dry cells in series and Figure 3.30 for dry cells
in parallel.

V V
3 V
3 V

A A

10 Ω 10 Ω

Figure 3.29 Figure 3.30

2. Record the voltmeter reading (total e.m.f. of dry cells), Ԑ in Table 3.14.
3. Close the switch. Record the ammeter and voltmeter readings (values of potential difference
across 10 W resistor).
4. Using the voltage drop, Ir = Ԑ – V, calculate the effective internal resistance, r for dry cells in
e
the series and the parallel arrangements. Complete the table.

LS 3.3.3 119