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. $0^{\circ }$
• B. ${30}^{\circ }$
• C. ${45}^{\circ }$
• D. ${90}^{\circ }$

Answer 1

The correct option is C ${45}^{\circ }$

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 $tan\varphi =\frac{B_V}{B_H}\Rightarrow tan\varphi =1\Rightarrow \varphi ={45}^{\circ }$