Page 74 - Physics_Form_2

Physics for Secondary Schools

Table 2.9 4. Change the resistance of the wire by
Time, varying its length, then, repeat steps
t (minutes) 2 and 3.
Temperature 5. Repeat step 4 and obtain at least
change, θ(°C) 2 more readings of change of
FOR ONLINE READING ONLY
temperature with the corresponding
Questions resistance of wire.
6. Determine the resistance of each
(a) Use ICT tools or otherwise, to plot
the graph of temperature, θ, against length of the wire and record the
time, t. results as shown in Table 2.10.
(b) Explain the nature of a graph.
Table 2.10
Heat absorbed by water is proportional to Length of
the increase of heating time. The graph of the wire, l
θ against t shows that, θ ∝ t, and H ∝ t.
Resistance of
the wire, ()R 

Temperature
Activity 2.12
change, θ(°C)
Aim: To observe the effect of
resistance on the heating Questions
effect of an electric current (a) Using ICT tools, plot a graph of

Materials: Battery, calorimeter with change in temperature, θ, against
jacket, thermometer, resistance, R.
resistive wire, ammeter, (b) Comment on the nature of the graph.
voltmeter, rheostat, The heat absorbed by water is
stopwatch, water, switch, proportional to the increase in
stirrer, connecting wires temperature. From the plot of change

Procedure in temperature against resistance, it

1. Set up an arrangement as shown in is observed that, θ, is proportional
Figure 2.37. to the resistance of the wire, thus,
2. Close switch S and adjust a rheostat θ ∝ R. Hence, H ∝ R. Therefore,
to obtain suitable values of I and from Activities 2.10 - 2.12, it can
V. Record the initial temperature of be concluded that,
water. H ∝ I Rt
2
3. Leave the current ON for a known
time and record the change in Hence,
2
temperature. H = kI Rt

68
Student’s Book Form One

Physics Form 2 Final.indd 68 25/10/2025 10:26