Question 2
AIM: To investigate the effect of resistance on voltage in a d.c. circuit.
- Connect the circuit as shown in Fig.1.
- Ask the supervisor to check the circuit connection.
- You are provided with Table 1
- Set the variable power supply to 6 V.
- Set the resistance box to 0 Ω.
- Close switch S.
- Read and record in Table 2 the ammeter and voltmeter readings.
- Set the resistance box to 2 Ω and repeat step (g).
- Repeat step (h) for the other resistance values in Table 2.
- Complete Table 2.
- Plot the graph of power (W) on the vertical axis against current squared (I2) on the horizontal axis.
- Determine the slope of the graph
Resistance |
Current |
Current Square |
Voltage |
Power = VI |
0.0 |
||||
2.0 |
||||
4.0 |
||||
6.0 |
||||
8.0 |
||||
10.0 |
Observation
The expected responses were:
TABLE 3
Resistance |
Current |
Current Square |
Voltage |
Power = VI |
0.0 |
0.19 |
0.036 |
6.0 |
1.1 |
2.0 |
0.18 |
0.032 |
5.6 |
1.0 |
4.0 |
0.17 |
0.029 |
5.3 |
0.9 |
6.0 |
0.16 |
0.026 |
5.0 |
0.8 |
8.0 |
0.15 |
0.023 |
4.8 |
0.7 |
10.0 |
0.14 |
0.019 |
4.5 |
0.6 |
- Correct circuit connection
- Correct reading of current I
- Correct reading of voltage V
- Completing current I2
- Graph sheet
- Axes
- Scale
- Points
- Line of best fit
-
The question required candidates to use the provided apparatus to set up a circuit. As in question 1, candidates were expected to read and record current and voltage readings in the table provided. The observations made for this question is similar to that of question one. Many candidates could not plot the graph nor determine the slope due to inaccurate values derived from the measuring instruments.