Question

A magnetic needle free to rotate in a vertical plane parallel to the magnetic meridian has its North tip pointing down at ${22}^0$ with the horizontal. the horizontal component of the earth's magnetic field at the place is known to be 0.35 G.The magnitude of the earth's magnetic field at the place will be:-

• A. 0.68 G
• B. 0.36 G
• C. 0.83 G
• D. 0.86 G

Answer 1

The correct option is B 0.36 G

$\begin{array}{c}H=0.35G,\theta ={22}^{\circ }\\ H=0.35G=0.35\times {10}^{-4}\\ H=B_e\cos \theta \\ B_e=\frac{0.35\times {10}^{-4}}{0.99}=0.36\times {10}^{-4}\\ =0.36G\end{array}$