Q: The area of the coil in a moving coil galvanometer is 16 cm^{2} and has 20 turns. The magnetic induction is 0.2 T and the couple per unit twist of the suspended wire is 10^{-6} Nm per degree. If the deflection is 45° calculate the current passing through it

Sol: Given, A = 16 cm^{2} = 16 × 10^{-4} m^{2}

B = 0.2 T ; N = 20 , K = 10^{-6} Nm/degree

θ = 45°

From, K θ = N i A B

$\large i = \frac{K \theta}{N B A} $

$\large i = \frac{10^{-6} \times 45}{20 \times 0.2 \times 16 \times 10^{-4} } $