Page 62 - Physics_Form_2

Physics for Secondary Schools

Procedure Questions
1. Connect an electric circuit as shown (a) Use an ICT tool or otherwise to
in Figure 2.26. plot the graph of p.d, V against the

current, I.
(b) What does the nature of the graph
FOR ONLINE READING ONLY
imply?
(c) Deduce the value of the unknown
resistor, R.
R

Example 2.7

A cell develops a potential difference
Figure 2.26 of 2 V across a resistor of 4 ohms.
Calculate the current flowing through
2. Close switch S and adjust the the resistor and the conductance of the
rheostat, Rh, so that a current of resistor.
0.1 A passes through the unknown
resistor, R. Solution
3. Use a spreadsheet or otherwise to Using Ohm’s law,
record the current, I and p.d, V.
4. Adjust the Rh to get a current of 0.2 V = IR , I = V
A passing through R. Record I and 2V R
V as in step 3. I   0.5 A
5. Repeat step 4 to obtain at least five 4 
more readings. Conductance G is the reciprocal of
6. Record the results in a table similar resistance
to Table 2.2. 1 1
G    0.25  1
Table 2.2 R 4
Therefore, the current flowing in the
Currently, p.d. V (volt)
I (ampere) resistor is 0.5A and the conductance of

the resistor is 0.25 .
1
0.1
0.2
0.3 Factors that determine the resistance
0.4 of a conductor
0.5 The resistance of a conductor is
0.6 determined by its temperature, length,

0.7 cross-sectional area and type of material.

56
Student’s Book Form One

Physics Form 2 Final.indd 56 25/10/2025 10:26