You are provided with a voltmeter V, a chemical cell/ battery E; two standard resistors R, and R a potentiometer a key K a jockey, and other necessary materials.
- Set up a circuit as shown in the diagram above.
- Close the key K.
- Make contact with the potentiometer wire AB using the jockey at a point C such that AC = x = 20cm
- Read and record the voltmeter reading
- Evaluate x\(^{-1}\) and v\(^{-1}\)
- Repeat the procedure for other values of x= 30, 40, 50, 60 and 80cm.
- Tabulate your readings.
- Plot a graph with V\(^{-1}\) on the vertical axis and x\(^{-1}\) on the horizontal axis, starting both axes from the origin (0, 0).
- Determine the:
(a) slope, s, of the graph;
(b) intercept, c, on the vertical axis. - State two precautions taken to ensure accurate results.
(b)i. State the two devices in which ohm’s law does not apply.
ii. A current of 1 A is supplied to two resistors of resistance 2\(\Omega\) and 3\(\Omega\) connected in parallel. Calculate the current in each resistor.
Explanation
| x/cm | v/volt | x\(^{1}\)/cm\(^{-1}\) | v\(^{1}\)/volts\(^{-1}\) |
| 20 | 0.15 | 0.050 | 6.667 |
| 30 | 0.20 | 0.033 | 5.000 |
| 40 | 0.30 | 0.025 | 3.333 |
| 50 | 0.40 | 0.020 | 2.500 |
| 60 | 0.50 | 0.016 | 2.000 |
| 80 | 0.60 | 0.013 | 1.667 |
Slope = \(\frac{6.667-1.667}{0.050-0.013} = \frac{5}{0.037}\)
= 135.135cm/volt
intercept = 0
Precautions;
- Tight connections /clean terminals was ensured
- Key removed when readings are not being taken.
- Parallex error avoided in reading voltmeter/ rule.
- Zero error noted and corrected for in the voltmeter/rule
- Dragging jockey along the wire avoided
