A potentiometer wire has length 4 m and resistance 8Ω.

Home » Electricity and Magnetism » Current Electricity » Question

A potentiometer wire has length 4 m and resistance 8Ω. The resistance that must be connected in series with the wire and an accumulator of e.m.f. 2V, so as to get a potential gradient 1 mV per cm on the wire is

1. 40 Ω
2. 44 Ω
3. 48 Ω
4. 32 Ω

Correct Option: D

Total potential difference across potentiometer wire
= 10^–3 × 400 volt = 0.4 volt
potential gradient = 1mv/cm
= 10^–3 v/cm = 10^–1(v/3)
Let resistance of RΩ connected in series.

⇒R + 8 = 40 or,R = 32 Ω