Two tangent galvanometers having coils of the same radius are connected in series. A current flowing in them produces deflections of $60° $ and $45°$  respectively. The ratio of the number of turns in the coils is

A tangent galvanometer shows a deflection $45^o $ when $10\, mA$ current pass through it. If the horizontal component of the earth’s field is $3.6 \times {10^{ - 5}}\,T$ and radius of the coil is $10\, cm$. The number of turns in the coil is......$turns$

Keeping dissimilar poles of two magnets of equal pole strength and length same side, their time period will be

In a vibration magnetometer, the time period of a bar magnet oscillating in horizontal component of earth's magnetic field is $2$ $sec$. When a magnet is brought near and parallel to it, the time period reduces to $1 $ $sec$. The ratio $H/F $ of the horizontal component $H$  and the field $F$ due to magnet will be

Two different magnets are tied together and allowed to vibrate in a horizontal plane. When their like poles are joined, time period of oscillation is $5 \,s$ and with unlike poles joined, time period of oscillation is $15 \,s$. The ratio of their magnetic moments is

The time period of a vibration magnetometer is $T_0$. Its magnet is replaced by another magnet whose moment of inertia is $3$ $times$ and magnetic moment is $1/3$ of the initial magnet. The time period now will be