QQuestion
The voltage-current readings of a certain material are shown in the table given below:
| Voltage (V) | Current (I) |
|---|---|
| 10 V | 2 A |
| 20 V | 3 A |
| 30 V | 4 A |
Study the table.
(a) State whether the conductor used is ohmic or non-ohmic.
(b) Justify your answer.
(c) State Ohm’s law.
✓Answer
(a) The conductor is non-ohmic.
(b) As, from Ohm’s Law
For V = 10 V and I = 2 A
R = \frac{\mathrm{V}}{\mathrm{I}} = \frac{10}{2} = 5 Ω ……. Equation 1
For V = 20 V and I = 3 A
R = \frac{\mathrm{V}}{\mathrm{I}} = \frac{20}{3} = 6.67 Ω ……. Equation 2
For V = 30 V and I = 4 A
R = \frac{\mathrm{V}}{\mathrm{I}} = \frac{30}{4} = 7.5 Ω ……. Equation 3
From equations 1, 2 and 3
Here, the ratio V/I is not constant and plot of V vs I graph will not be linear but if a conductor is an ohmic conductor then V/I should be constant to follow Ohm’s law and V vs I graph should be linear which is not the case here.
Hence, the conductor does not follow Ohm’s law and is a non-ohmic conductor.
(c) Ohm’s law states that the current flowing through the conductor is directly proportional to the potential difference across its ends provided that the physical conditions and the temperature of the conductor remain constant.
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