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 is connected in parallel with both the resistors

Answer 1

Answer: (A), (C)

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

$\text{Solution}:$

The range of voltmeter V is given by the experession

$V=I_g[R_c+(R_c+R+R\left)\right]$

V is max in this case as RHS is maximum.

Thus (a) is correct.

The range of ammeter I is given by the expression

$I=\frac{I_g{R}_c}{R_{eq}}+I_g$

Where $\frac{1}{R_{eq}}=\frac{1}{R_c}+\frac{1}{R}$

Here $R_{eq}$ is minimum and therefore I is maximum.

Thus(c) is the correct option.

$\text{Hence A and C are the correct option}$