Question

T0 is time period of oscillation of the needle in uniform horizontal magnetic field (B h) of earth. If another magnetic field is applied perpendicular to B, such that the needle deflects by theta for its equilibrium. Now period of oscillation of needle is T. The relation between Tand T0 id​

Answer 1

t=2t0

Let  V be the volume of the bob.

Thus mass of the bob       M=ρbV=34×1000Vkg

Acceleration due to gravity in air is  g.

Effective weight of the bob in water       Mg′=Mg−B       where  buoyant force  B=(Vρwater)g

34×1000Vg′=34×1000Vg−V×1000g                       (as ρ