Question

In the following circuit a 10 m long potentiometer wire with resistance 1.2 ohm/m, a resistance R₁ and an accumulator of emf 2 V are connected in series. When the emf of thermocouple is 2.4 mV then the deflection in galvanometer is zero. The current supplied by the accumulator will be

• A. 4 × 10^–4A
• B. 8 × 10^–4A
• C. 4 × 10^–3A
• D. 8 × 10^–3A

Answer 1

Answer: (A)

4 × 10^–4A

Answer 2

$E = x l = i \rho l$

∴ $i = \frac { E } { \rho l } = \frac { E } { \rho l } = \frac { 2.4 \times 10 ^ { - 3 } } { 1.2 \times 5 } = 4 \times 10 ^ { - 4 } \mathrm {~A}$.