Page 58 - Physics_Form_2

Physics for Secondary Schools

1 (A ) 2. Set R at 10 Ω, close switch S and read
−1
I the ammeter and record current, I.
3. Repeat step 2 for R = 8 Ω, 6 Ω, 4 Ω
r
E and 2 Ω.
4. Using a spreadsheet or otherwise,
FOR ONLINE READING ONLY
record results as shown in Table 2.6.
-r (Ω) R (Ω)
Table 2.6

Resistance, Current, 1
R (Ω) I (A) I (A  1 )

10
Figure 2.21: The graph of the reciprocal of 8

current, 1 against resistance, R
I 6
4
The following activity 2.3 will aid on 2
practical understanding in measurement
of e.m.f and internal resistance.
Questions
Activity 2.3 (a) Use ICT software or otherwise to
1
Aim: To determine the plot a graph of R against .
I
electromotive force, E, and (b) Determine the vertical intercept.
internal resistance, r, of a (c) What is the value of r?
cell (d) Determine the slope of the graph.

Materials: A cell, a set of standard (e) What is the value of E?
resistors (2-10 Ω), an
ammeter, a switch Example 2.6
Procedure
An electric cell with minimal voltage,
1. Connect the circuit as shown in Figure E , has a resistance of 3 Ω connected
m
2.22. across it. If the voltage falls to 0.6 E,
E calculate the internal resistance of this
cell.

Solution
Given:
R S
E  , ER  0.6E
3 , V 
m
Figure 2.22
52
Student’s Book Form One

Physics Form 2 Final.indd 52 25/10/2025 10:26