In a galvanometer,the deflection becomes one half when the galvanometer is shunted by a $20\,\Omega$ resistor. The galvanometer resistance is ............... $\Omega$.

By connecting a resistance of $980 \Omega$ in series with a galvanometer, it is converted into a voltmeter of a certain range. When the resistance of $470 \Omega$ is connected in series, the range is halved. 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 $50 \ \Omega$ giving full scale deflection for a current of $10 \ mA$ is to be changed into a voltmeter of range $100 \ V$. $A$ resistance of . . . . . . $\Omega$ has to be connected in series with the galvanometer.

$A$ galvanometer coil has a resistance of $50 \Omega$ and the meter shows full scale deflection for a current of $5 \text{ mA}$. This galvanometer is converted into a voltmeter of range $0-20 \text{ V}$ by connecting:

$A$ current of $10^{-3} \ A$ is flowing through a resistance of $1000 \ \Omega$. To measure the correct potential difference across this resistance,a voltmeter must be used whose resistance should be: