$A$ galvanometer has a resistance of $50 \ \Omega$ and it allows a maximum current of $5 \ mA$. It can be converted into a voltmeter to measure up to $100 \ V$ by connecting in series a resistor of resistance: (in $\Omega$)

The resistance of an ideal ammeter is

With a resistance '$X$' connected in series with a galvanometer of resistance $100 \Omega$, it acts as a voltmeter of range $0 - 15 \text{ V}$. To double the range, a resistance of $1500 \Omega$ is to be connected in series with '$X$'. The value of '$X$' in $\Omega$ is

Two moving coil meters,$M_{1}$ and $M_{2}$ have the following particulars:
$R_{1}=10 \,\Omega, \quad N_{1}=30$
$A_{1}=3.6 \times 10^{-3} \,m^{2}, \quad B_{1}=0.25 \,T$
$R_{2}=14 \,\Omega, \quad N_{2}=42$
$A_{2}=1.8 \times 10^{-3} \,m^{2}, \quad B_{2}=0.50 \,T$
(The spring constants are identical for the two meters). Determine the ratio of
$(a)$ current sensitivity and
$(b)$ voltage sensitivity of $M_{2}$ and $M_{1}$.

The resistance of an ammeter is $13\, \Omega$ and its scale is graduated for a current up to $100\, A$. After an additional shunt has been connected to this ammeter,it becomes possible to measure currents up to $750\, A$ by this meter. The value of the shunt resistance is:

$A$ moving coil sensitive galvanometer shows a large deflection. To control its speed of deflection (damping),which of the following is used?