MHT CET · Physics · Current Electricity

The scale of a galvanometer is divided into 160 equal divisions. The galvanometer shows full scale deflection of 16 mA and maximum voltage is 80 mV . Now the range is changed so that galvanometer reads 160 V . The required resistance to be connected is

A \(9995 \Omega\) in series.
B \(4995 \Omega\) in series.
C \(9.5 \times 10^{-3} \Omega\) in parallel.
D \(4.95 \times 10^{-3} \Omega\) in parallel.

Verified Solution

Answer & Solution

Correct Answer

(A) \(9995 \Omega\) in series.

Step-by-step Solution

Detailed explanation

\(R_g = \frac{V_g}{I_g} = \frac{80 \times 10^{-3} \text{ V}}{16 \times 10^{-3} \text{ A}} = 5 \, \Omega\) \(R_s = \frac{V}{I_g} - R_g = \frac{160 \text{ V}}{16 \times 10^{-3} \text{ A}} - 5 \, \Omega = 10000 - 5 = 9995 \, \Omega\)

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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