1. **Set up the circuit:** Connect the power supply in series with the switch, the ammeter, and the resistance wire. Connect the voltmeter in parallel across the section of the wire being measured.
2. **Initial measurement:** Attach one crocodile clip to the wire at the 0 cm mark. Attach the second crocodile clip at a specific length, e.g., 10 cm, using the ruler to measure the length accurately.
3. **Take readings:** Close the switch and record the reading on the ammeter (current, I) and the voltmeter (potential difference, V).
4. **Calculate resistance:** Calculate the resistance using the formula R = V / I.
5. **Repeat for different lengths:** Open the switch, move the second crocodile clip to a new length (e.g., 20 cm, 30 cm, 40 cm, etc.) and repeat steps 3 and 4 for a range of different lengths.
6. **Control variables:** To ensure the temperature remains constant, the switch should be opened between readings to prevent the wire from heating up. Use a low potential difference.
7. **Record data:** Record the length, potential difference, current, and calculated resistance in a suitable table.
To investigate the relationship between the length of a wire and its resistance, a circuit is needed to measure the potential difference (V) across the wire and the current (I) flowing through it.
- **Circuit:** The ammeter must be connected in series with the wire to measure the current flowing through it. The voltmeter must be connected in parallel across the specific length of wire being tested to measure the potential difference across it.
- **Procedure:**
1. Connect the circuit as described.
2. Attach crocodile clips to the wire to select a specific length (L), measured with a ruler.
3. Close the switch, record V and I.
4. Calculate resistance R = V/I.
5. Repeat for at least 5 different lengths, e.g., 20cm, 40cm, 60cm, 80cm, 100cm.
- **Control Variable:** The temperature of the wire must be kept constant, as resistance changes with temperature. This can be achieved by using a low current and turning off the power between readings to prevent the wire from heating up.
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