Question

The voltage - current readings of a certain material are shown in the table given below:

Voltage (V)	10 V	20 V	30 V
Current (I)	2 A	3 A	4 A

Study the table.

1. State whether the conductor used is ohmic or non-ohmic.
2. Justify your answer.
3. State Ohm's law.

Answer 1

a. Here, the ratio of `V/1` for different readings is:

(i) `(10 V)/(2 A) = 5 Ω`

(ii) `(20 V)/(3 A) = 6.66 Ω`

(iii) `(30 V)/(4 A) = 7.5 Ω`

Here, the ratio is not constant, so the conductor is non-ohmic.

b. The ratio of `V/I` remains constant for all values of V and I in an ohmic conductor. Plotting current I against potential difference V results in a straight line that passes through the origin on a graph. Thus, the conductor in question is not ohmic.

c. Ohm's law states that, under constant physical conditions and conductor temperature, the current flowing in a conductor is directly proportional to the potential difference applied across its ends.