In a moving coil galvanometer, two moving coils M1 and M2 have the following particulars: R1 = 5 Ω, N1 = 15, A1 = 3.6 × 10-3 m2, B1 = 0.25 T R2 = 7 Ω, N2 = 21, A2 = 1.8 × 10-3 m2, B2 = 0.50 T Assuming that the torsional constant of the springs is the same for both coils, what will be the ratio of the voltage sensitivity of M1 and M2?

A solenoid of length 0.4 m having 500 turns of wire carries a current of 3 A. A thin coil having 10 turns of wire and radius 0.1 m carries a current of 0.4 A. The torque required to hold the coil in the middle of the solenoid with its axis perpendicular to the axis of the solenoid is (Take μ0 = 4π × 10-7 SI units, π2 = 10, sin(90°) = 1):

An electron makes one full rotation in a circular path of radius 0.8 m in one second. The magnetic field at the centre of the circle is: (μ0 = 4π × 10-7 T·m/A)