Question

A tangent galvanometer carrying a current of $0.8A$ gave a deflection of ${30}^o$. If the earths horizontal component of magnetic induction were to suddenly become one third of the usual value, the deflection for the same current will be

• A. ${60}^o$
• B. ${45}^o$
• C. ${90}^o$
• D. ${30}^o$

Answer 1

Answer: (A)

${60}^o$

$B_4\tan \theta =\frac{{\mu }_{0}i}{2r}$
$\frac{\tan {\theta }_1}{\tan {\theta }_2}=\frac{B_{4_2}}{B_{4_1}}$
$\frac{\tan {30}^o}{\tan {\theta }_2}=\frac{\left(\frac{1}{3}\right)}{1}$
$\tan {\theta }_2=\sqrt{3}$
${\theta }_2={60}^o$