Question 1
AIM: To demonstrate Ohm’s law.
- Connect the circuit as shown in figure 1.
- Ask the supervisor to check the circuit connection.
-
Table 1
Copy Table 1 into your answer booklet.
Current (A)Potential diff. (V)
2.00
1.80
1.60
1.20
1.00
- Adjust the power supply unit to 20V and maintain this voltage throughout the experiment.
- Vary the rheostat to indicate a current of 2A on the ammeter.
- Repeat and record the corresponding value of voltage (V)
- Repeat steps (e) and (f) for the other current values on Table 1.
- Plot a graph of potential difference (V) on the vertical axis against current (A) on the horizontal axis
- Determine the slope of the graph.
- Compare the value of the slope in (i) with the value of the fixed resistor.
Observation
The expected answers were:
TABLE 1
Current (A) |
Potential diff. (V) |
2.0 |
20 |
1.8 |
18 |
1.6 |
16.6 |
1.2 |
12 |
1.0 |
10 |
- Correct reading of potential difference (V)
- Correct axes
- Reasonable scale
- Plotting of points
- Line of best fit
- Determination of slope
- Comparison of slope and value of fixed resistor (the two are the same)
The question required candidates to demonstrate Ohm’s law. The procedure for carrying out this experiment was provided. Many of the candidates were able to conduct the experiment, obtained the readings and plotted the graph. It is only in the area of accuracy of their readings that they did not do well.