To verify Ohm's law,a student is provided with a test resistor $R_T$,a high resistance $R_1$,a small resistance $R_2$,two identical galvanometers $G_1$ and $G_2$,and a variable voltage source $V$. The correct circuit to carry out the experiment is

The coil of a moving coil galvanometer has an effective area of $4 \times 10^{-2} \, m^2$. It is suspended in a magnetic field of $5 \times 10^{-2} \, Wb \, m^{-2}$. If the deflection in the galvanometer coil is $0.2 \, rad$, when a current of $5 \, mA$ is passed through it, then

The current sensitivity of a moving coil galvanometer is increased by $25 \%$. This increase is achieved only by changing the number of turns of the coils and the area of the cross-section of the wire while keeping the resistance of the galvanometer coil constant. The percentage change in the voltage sensitivity will be $...........\%$

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,having a resistance of $50 \Omega$,gives a full scale deflection for a current of $0.05 \text{ A}$. The length in metre of a resistance wire of area of cross-section $2.97 \times 10^{-2} \text{ cm}^2$ that can be used to convert the galvanometer into an ammeter which can read a maximum of $5 \text{ A}$ current is: (Specific resistance of the wire $= 5 \times 10^{-7} \Omega\text{-m}$)

An ideal ammeter and an ideal voltmeter have resistances of . . . . . . $\Omega$ and . . . . . . $\Omega$ respectively.