Question 2
AIM: To demonstrate the relationship between current, voltage and power in a d.c. circuit.
- Connect the circuit as shown in figure 2.
- Ask the supervisor to check the circuit connection.
- Copy Table 2 into your answer booklet
Table 2
Voltage (Vs) |
Voltage drop across R2 (VR2) |
Current (A) |
Power (W) |
12 |
|
|
|
10 |
|
|
|
8 |
|
|
|
6 |
|
|
|
4 |
|
|
|
2 |
|
|
|
- Adjust the power supply to 12V.
- Read and record the current (A) and voltage drop across the resistor R2.
- Repeat steps (d) and (e) for other values of voltage in Table 2.
- Complete Table 2.
- Compare the voltage drop across R2 and the power calculated.
Observation
The expected answers were:
- Correct circuit connection
TABLE 2
Voltage (Vs) |
Voltage drop across R2 (VR2) |
Current (A) |
Power (IVR2) |
12 |
6 |
0.6 |
3.6 |
10 |
5 |
0.5 |
2.5 |
8 |
4 |
0.4 |
1.6 |
6 |
3 |
0.3 |
0.9 |
4 |
2 |
0.2 |
0.4 |
2 |
1 |
0.1 |
0.1 |
Correct entries under
- Voltage drop (VR2)
- Current (A)
- Power (W)
- Voltage drop across R2 and power calculated: As VR2 decreases, power decreases.
This question sought to demonstrate the relationship between current, voltage and power in a d.c circuit. The strengths and weaknesses exhibited by candidates in question1are similar to the ones here as well in relation to understanding what is expected of them and taking accurate readings. Candidates were able to make reasonable comments on the relationship between voltage drop across R2 and power calculated.