Question 2
AIM: To determine the resistance of a resistor using power-current relationship.
Figure 2
- Connect the circuit as shown in figure 2.
- Ask the supervisor to check the circuit connection.
- You are provided with Table 2.
Table 2
Switch on the power supply unit.
- Set the power supply unit to 0V and close the switch (s)
- Read and record the corresponding ammeter and voltmeter readings.
- Repeat steps (e) and (f) for the other values in Table 2.
- Open switch (s) and switch off the power supply unit
- Complete Table 2.
- Plot a graph of power (W) on the vertical axis against I2 on the horizontal axis.
- Calculate the slope of the graph.
- Determine the resistance of the resistor.
Observation
The expected answers were:
VOLTAGE (VS) |
0.0 |
1.0 |
2.0 |
3.0 |
4.0 |
5.0 |
6.0 |
7.0 |
8.0 |
CURRENT (mA) |
0.0 |
213 (0.213) |
426 |
638 |
871 |
106.4 |
1272 |
1489 |
1702 |
VOLTAGE (VR2) |
0.0 |
1.0 |
2.0 |
3.0 |
4.0 |
5.0 |
6.0 |
7.0 |
8.0 |
POWER (IVR2) |
0.0 |
0.2 |
0.9 |
1.9 |
3.5 |
5.3 |
7.6 |
10.4 |
10.6 |
I2 |
0.0 |
45369 |
181476 |
407044 |
758641 |
1132096 |
1617984 |
2217121 |
2896804 |
TABLE 2
- Correct circuit connection
- Correct current readings
- Correct voltage readings
- Calculation of Power (W)(IVR2)
- Calculation of I2
- Correct Axis
- Reasonable scale
- Correct points
- Line of best fit
- Determination of slope
- Value of resistor
This question is to determine the value of an unknown resistor using the power-current relationship. Candidates were expected to take voltage and current readings in other to determine power. The strengths and weaknesses exhibited by candidates in question 1are similar to the ones here as well in relation to understanding what is expected of them and inability to take accurate readings