$A$ voltmeter of resistance $R$ is to be used to measure the potential difference across a resistance $r$. In which case will the reading be nearest to the actual potential difference in the absence of the voltmeter?

The sensitivity of a galvanometer that measures current is decreased by $\frac{1}{40}$ times by using a shunt resistance of $10 \Omega$. Then,the value of the resistance of the galvanometer is (in $\Omega$)

Consider the two following statements $A$ and $B$, and identify the correct choice given in the answers: $(A)$ Duddell's thermo galvanometer is suitable to measure direct current only. $(B)$ Thermopile can measure temperature differences of the order of $10^{-3} {}^{\circ}C$.

$A$ galvanometer of resistance $G$ is shunted by a resistance $S$. To keep the main current in the circuit unchanged,the resistance to be put in series with the galvanometer is

$A$ galvanometer of $10 \,\Omega$ resistance gives full scale deflection with $0.01 \, A$ of current. It is to be converted into an ammeter for measuring $10 \, A$ current. The value of shunt resistance required will be

The ratios of the voltage sensitivities,resistances and areas of the coils of two moving coil galvanometers $A$ and $B$ are $4:3$,$3:4$ and $1:2$ respectively. If the number of turns of the coil of galvanometer $A$ is $200$,then the number of turns of the coil of galvanometer $B$ is (All other quantities remain same in both the cases)