Question

At a certain place a bar magnet makes 30 oscillations per minute.At another place where the magnetic field is double, time period of its oscillations will be

Answer 1

we know, time period of oscillation of bar magnet in magnetic field is given by , $T=2\pi\sqrt{\frac{I}{MB}}$

where I is moment of inertia, M is magnetic moment and B is magnetic field intensity.

if I and M are constant then, time period of bar magnet is inversely proportional to square root of magnetic field.

i.e., $\frac{T_1}{T_2}=\sqrt{\frac{B_2}{B_1}}$

bar magnet makes 30 oscillations /min

so, bar magnet makes 2 oscillations in a second. e.g., time period , $T_1$= 2 sec

now, $\frac{2}{T_2}=\sqrt{\frac{2B}{B}}$

or, $T_2=\sqrt{2}$ sec