The current I em units, flowing in a coil of a tangent galvanometer is given by the expression where
r = Mean radius of the galvanometer coil.
N = Numberof turns of the galvanometercoil.
H = Horizontal componentof earth magneticfield.
$$\phi$$ = Deflection of galvanometer magnetic needle.

A

$$I = \left(\frac{Hr}{2 \pi N}\right)^* \cos \phi$$

B

$$I = \left(\frac{2 \pi Nr}{H}\right)^* \tan \phi$$

C

$$I = \left(\frac{Hr}{2 \pi N}\right)^* \tan \phi$$

D

$$I = \left(\frac{2 \pi Nr}{H}\right)^* \cos \phi$$