Question 1
AIM: To determine the resistance of a resistor using Voltage-current relationship.
- Connect the circuit as shown in figure 1.
- Ask the supervisor to check the circuit connection.
-
Table 1
You are provided with Table 1.
- Switch on the power supply unit.
- Set the power supply unit to 0 V and close the switch(s).
- Read and record the corresponding ammeter and voltmeter readings in Table 1.
- Repeat steps (e) and (f) for the other values in Table 1.
- Open switch(s) and switch off the power supply unit.
- Plot a graph of current (I) on the vertical axis against voltage (VR1) on the horizontal axis
- Calculate the slope of the graph.
- Determine the resistance of the 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.