You are provided with a constantan wire, a 2\(\Omega\) standard resistor, an accumulator E, an ammeter A, a key K, and other necessary apparatus.
- Measure and record the e.m.f.of the accumulator provided.
- Connect a circuit as shown in the diagram above.
- Close the key, read and record the ammeter reading l\(_{o}\) when the crocodile clip is not in contact with the constantan wire.
- Open the key. With the clip making contact with the wire, when I = 90cm, close the key. Read and record the ammeter reading /. Evaluate l\(^{-1}\).
- Repeat the procedure for l= 80, 70, 60 and 50cm.
- In each case, read and record the ammeter reading and evaluate l\(^{-1}\). Tabulate your readings.
- Plot a graph of l on the vertical axis against l\(^{-1}\) on the horizontal axis.
- Determine the slope, s, of the graph and its intercept, c on the vertical axis.
- Evaluate k = \(\frac{c}{s}\).
- Using your graph, determine the Current i when / = 55cm.
- State two precautions taken to ensure accurate results.
(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 resistance wire depends.
Explanation
Table of values (Observation)
| l\(_{o}\) (amps) | l(cm) | l\(^{-1}\) | l(amps) |
| 0.65 | 90 | 0.011 | 0.70 |
| 0.70 | 80 | 0.013 | 0.75 |
| 0.75 | 70 | 0.014 | 0.80 |
| 0.80 | 60 | 0.017 | 0.85 |
| 0.85 | 50 | 0.020 | 0.90 |
7.
(8). Slope (s) = \(\frac{\bigtriangleup {I}}{\bigtriangleup {/}^{-1}} = \frac{0.65}{0.024}\) = 27.1
(9). Intercept (c) on the vertical axis = 0.43 amps
(10). Evaluate, K = \(\frac{c}{s} = \frac{0.43}{27.1}\) = 0.016
(11) The value of the current l when l = 55cm, l\(^{-1}\) = 0.018cm,
Therefore; l on the graph = 0.875 amps
Precautions:
- The key was removed when the reading were not being teken.
- I ensured that terminals were clean.
- I ensured that the connetions were tight.
- Zero error was noted and corrected in the ammeter/ metre rule
- Parallax error was avoided in anmmeter/metre rüle.
(b)i. The potential differenoe between two points in an electric ciroult the work done in Joules when one coulomb of electric charge moves from one point to the other
ii. Factors on which the resistance of a resistance wire depends are:
- resistivity of the wire/ nature of the wire
- length of the wire.
- cross sectional area of the wire /thickness of the wire.
- temperature