Question

Consider two identical galvanometers and two identical resistors with resistance $R$. If the internal resistance of the galvanometers $R_C<R/2$, which of the following statement(s) about any one of the galvanometers is(are) true?

• A. The maximum voltage range is obtained when all the components are connected in series
• B. The maximum voltage range is obtained when the two resistors and one galvanometer are connected in series, and the second galvanometer is connected in parallel to the first galvanometer
• C. The maximum current range is obtained when all the components are connected in parallel
• D. The maximum current range is obtained when the two galvanometers are connected in series and the combination in parallel with both the resistors

Answer 1

Answer: (A), (C)

The maximum current range is obtained when all the components are connected in parallel

For maximum voltage,
let the current through the galvanometer is $I_g$

$V_{max}=I_g(2R+{2R}_C)$

This would happen when all components are in series, and in option B the equivalent resistance will be less than the series arrangement and so maximum voltage cannot be obtained

For maximum current,

when all the resistance is connected in parallel, those resistance will act as a shunt for that galvanometer

Answer is A and C options.