Question

A TG has $50$ turns each of diameter $15cm$. When a certain current is passed through its coil, the deflection of the needle is ${45}^o$ . If $B_H=4\pi \mu T,$ the value of current is

• A. $77.44mA$
• B. $44.77mA$
• C. $74.74mA$
• D. $30mA$

Answer 1

The correct option is A $77.44mA$

$B_4\tan \theta =\frac{n{\mu }_{0}i}{2r}$
$4\pi \times \tan {45}^o=\frac{50\times \mu \times i}{2\times \frac{15}{2}\times {10}^{-2}}$
$I=77\cdot 44mA$