Question

A dip needle vibrates in the vertical plane perpendicular to the magnetic meridian. The time ** of vibration is found to be 2 sec. The same needle is then allowed to vibrate in the horizontal plane and the time ** is again found to be 2 sec. Then the angle of dip is

(a) 0°

(b) 30°

(c) 45°

(d) 90°

Answer 1

The correct option (c) 45°

Explanation:

In the vertical plane T = 2π √[I/(MBV)] (1)

In the horizontal plane T = 2π √[I/(MBH)] (2)

Given T = 2sec in both cases, hence equation (1) & (2)

∴ √[I/(MBV)] = √[I/(MBH)]

∴ (BV/BH) = 1

but (BV/BH) = tanɸ

hence tanɸ = 1

ɸ = 45°

Hence angle of dip is 45°