You are provided with a constantan wire, a2 \(\Omega\)standard resistor, an accumulator E, an ammeter A, a key K, and other necessary apparatus.
(b)i. Explain what is meant by the potential difference between two points in an electric circuit.
ii. State two factors on which the resistance of a wire depends.
| d/cm | I/A | d\(^{-1}\)/cm\(^{-1}\) |
| 80.0 | 0.23 | 0.0125 |
| 70.0 | 0.25 | 0.0143 |
| 60.0 | 0.31 | 0.0167 |
| 50.0 | 0.34 | 0.0200 |
| 40.0 | 40.0 | 0.0250 |
Slope, SI = \(\frac{\bigtriangleup {I}}{\bigtriangleup {d}^{-1}}\) = \(\frac{0.40-0.13}{0.024-0.006}\)
= \(\frac{(0.27)A}{(0.018)cm^{-1}}\)
= 15A/cm\(^{-1}\)
Intercept C on the vertical axis = 0.04A
k = c/s = \(\frac{0.04}{15}\) = 0.00267 = 2.67 x 10\(^{-3}\)
From the graph, when d = 55cm, I = 0.31A
Precautions; I
- ensured that the keys was open after each reading so that the battery did not run down quickly.
- ensured there was zero error when taking the ammeter reading.
- Key was removed when readings were not being taken
- ensured terminals are clean/tight
- Noted and corrected/avoided zero error on ammeter metre rule
(b)i. The potential difference between two points in an electric circuit is the work done (in joules) when one coulomb of electric charge moves from one point to the other
ii. - Nature of wire/resistivity
- Length of wire
- Cross-sectional area of wire/thickness of wire
- Temperature
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