Question

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

• A. 0⁰
• B. 30⁰
• C. 45⁰
• D. 90⁰

Answer 1

Answer: (C)

45⁰

Answer 2

In vertical plane perpendicular to magnetic meridian.

$T = 2 \pi \sqrt { \frac { I } { M B _ { V } } }$ ......(i)

In horizontal plane $T = 2 \pi \sqrt { \frac { I } { M B _ { H } } }$ .....(ii)

Equation (i) and (ii) gives $B _ { V } = B _ { H }$

Hence by using $\tan \phi = \frac { B _ { V } } { B _ { H } } \Rightarrow \tan \phi = 1 \Rightarrow \phi = 45 ^ { \circ }$