Question

A potentiometer has uniform potential gradient. The specific resistance of the material of the potentiometer wire is 10^-9Ωm and the current passing through it is 0.5A and the cross sectional area of the wire is 10^-8m^2. Calculate the potential gradient along the potentiometer wire.

(a) 0.5 × 10^-9 V/m

(b) 0.5 × 10^-8 V/m

(c) 0.5 × 10^-1 V/m

(d) 0.5 × 10^-15 V/m

I got this question at a job interview.

The query is from Current Electricity in chapter Current Electricity of Physics – Class 12

Answer 1

Correct option is (c) 0.5 × 10^-1 V/m

The explanation: Resistance of a wire = \(\frac {Ꝭl}{A}\), where Ꝭ is the specific resistance of the material of the wire.

Potential gradient = \(\frac {V}{l} \rightarrow \frac {IR}{l}\) → \(\frac {I(\frac {Ꝭl}{A})}{l}\)

= \(\frac {Ꝭl}{A}\)

= 0.5 × \(\frac {10^{-9}}{10^{-8}}\)

= 0.5 × 10^-1 V/m

Therefore, the potential gradient is equal to 0.5 × 10^-1 V/m.