For full scale deflection of total 50 divisions, 50 mV voltage is required in galvanometer. The resistance of galvanometer if its current sensitivity is 2 div/mA will be :

Solution

Physics sir · 3 steps

First get the full-scale current from the sensitivity, then Ohm's law gives the resistance at once.

1. Full-scale current. Current sensitivity is 2 divisions per mA, so 1 mA moves the needle 2 divisions. For all 50 divisions the current must be 50/2 = 25 mA.
2. Use Ohm's law. The same full-scale deflection needs 50 mV across the galvanometer. Voltage and current both belong to the full-scale state, so divide one by the other.

   G = V/I_g = (50 × 10⁻³ V)/(25 × 10⁻³ A) = 2 Ω

3. So. The galvanometer resistance is 2 Ω, which is option (d).

The idea to keep. Sensitivity is divisions per unit current (or voltage). Divide the total divisions by it to get the full-scale value, then G = V/I_g links the two.

Answer from the NTA final answer key. Solution by PrepWiser.