You are provided with cells, a potentiometer, an ammeter, a voltmeter, a bulb, a key, a jockey, and other necessary materials.
i. Measure and record the e.m.f E of the battery.
ii. Set up a circuit as shown in the diagram above.
iii. Close the key K and use the jockey to make a firm.
iii. Contact at J on the potentiometer wire such that PJ = x= 10cm.
iv. Take and record the voltmeter reading V and the () Corresponding ammeter reading.
v. Evalute log V and log I.
vi. Repeat the procedure for five other values of x = 20 cm, 30 cm, 40 cm, 50 cm, and 60 cm.
vii. Tabulate your readings.
viii. Plot a graph with log I on the vertical axis and log V on the horizontal axis.
ix. Determine the slope s, of the graph.
x. Determine the intercept, c, on the vertical axis.
xi. State two precautions taken to ensure accurate results.
(b)i. How is the brightness of the bulb affected as x increases?
ii. List two electrical devices whose actions do not obey Ohm’s law.
Explanation
| S/N | I/A | V/V | LogV/V | LogI/A |
| 1.0 | 0.10 | 0.30 | -0.552 | -1.000 |
| 2.0 | 0.15 | 0.50 | -0.301 | -0.823 |
| 3.0 | 0.20 | 0.70 | -0.154 | -0.698 |
| 4.0 | 0.25 | 0.80 | -0.096 | 0.602 |
| 5.0 | 0.30 | 0.90 | -0.045 | 0.522[ |
Slopes S = \(\frac{\bigtriangleup \text{logI}}{\bigtriangleup \text{logV}}\) = \(\frac{\text{logl}_{2}} {\text{logV}_{2}}\) - \(\frac{\text{logl}_{1}}{\text{logV}_{2}}\)
S = \(\frac{-1.00 - (-0.70)}{-0.15 - (0.50)}\) = \(\frac{0.30}{0.10}\)
S= 3
PRECUATIONS
1. avoided parallax error when reading ammeter and voltmeter
2. opened the key when readings are not being taken to ensure that the cells do not run down.
3. ensured that the jockey is not dragged along the potentiometer wire.
(b)i. As x increases, the brightness of the bulb increases. As x increases, voltage and current through the bulb also increases, hence brightness increases
ii. Electrical devices whose action does not obey ohm's law. They are: Diode, Capacitor, Transistor, Thermistor and Thyristor.
