A moving iron instrument has L(θ) = 0.01 + 0.005θ2 H. Find the deflecting torque at θ = 2 rad when I = 3 A.

A D'Arsonval galvanometer has flux density = 8 × 10-3 Wb/m2, number of turns = 300, length of coil = 15 mm, width of coil = 30 mm, spring constant = 2.5 × 10-9 Nm/rad, moment of inertia = 10 × 10-9 kg-m2, damping constant = 2 × 10-9 Nm/rad-s-1, and resistance of coil = 80 Ω. What is the deflection of the galvanometer for a current of 1 μA?

A 5 A ammeter has an internal resistance of 0.1 Ω. What value of shunt resistance is required to extend its range to 25 A?