Question

A tangent galvanometer has a coil with 50 turns and radius equal to 4 cm. A current of 0.1 A is passing through it. The plane of the coil is set parallel to the earth's magnetic meridian. If the value of the earth's horizontal component of the magnetic field is $7 \times 10 ^ { - 5 }$ tesla and

, then the deflection in the galvanometer needle will be

• A. 45^o
• B. 48.2^o
• C. 50.7^o
• D. 52.7^o

Answer 1

Answer: (B)

48.2^o

Answer 2

For tangent galvanometer

$I = \frac { 2 r B } { \mu _ { 0 } n } \tan \theta$

$\therefore \tan \theta = \frac { I \mu _ { 0 } n } { 2 r B } = \frac { 0.1 \times 4 \pi \times 10 ^ { - 7 } \times 50 } { 0.04 \times 7 \times 10 ^ { - 5 } \times 2 } = 1.12$

or $\theta = \tan ^ { - 1 } ( 1.12 ) = 48.2 ^ { \circ }$