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.
(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.
More ICSE Easy level questions
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When a current I flows through a wire of resistance R for time t then the electrical energy produced is given by: (a) I2Rt (b) IR2t (c) IRt (d) IRt2
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In a closed circuit containing a bulb and a cell, the electromotive force (ε) and the terminal voltage (V) is related as. (Given I is current and r is internal resistance.) (a) V = ε + Ir (b) V = ε – Ir (c) V = ε ÷ Ir (d) V = ε × Ir
Choose the correct relation for e.m.f. (ε) and terminal voltage V: (a) ε = V [always] (b) V > ε [always] (c) V < ε [when the cell is in use] (d) None of these
A resistance R is connected across a cell with a switch and a rheostat in series. A voltmeter is connected parallel across the cell. Current in the circuit is increased using the rheostat. (a) How will the voltmeter reading change? (increase / decrease / remain the same) (b) Justify your answer stated in (a) above.
A current flows through a metallic conductor for a long period of time. State the change you would expect in its: (a) Resistance (b) Resistivity
