Given,Number of turns, N = 20 Radius of the coil, r = 10 cm = 10 x 10–2 mMagnetic field, B = 0.10 TCurrent carried, I = 5.0 Aθ = 0° (angle between field and normal to the coil)Area of the coil, A = πr2                           = π x (10 x 10–2)2                          = π x 10–2 m2(a) Torque, τ = NIBA sin θ                   = 20 x 5.0 x 0.10 x π x 10–2 sin 0°                   = 20 x 5.0 x 0.10 x π x 10–2 x 0 = 0(b) Net force on a planer current loop in a magnetic field is always zero, as net force due to couple of force is zero. (c) If vd is the drift velocity of electron                       F = qv x B                         = evd. B sin 90°Force on one electron = Be  vd = BeIneA = BInAHere,                       n = 1029 m-3,   A  =10-5m2∴ Force on one electron = 0.10 × 5.01029 × 10-5 = 5 × 10-25N.