A rigid rectangular loop, with sides PQ = RS = a = 20 cm and QR = SP = b = 10 cm, has a mass per unit of length = 5-10-2g/cm and is crossed by a current i. It can rotate without friction around PQ which is parallel to the horizontal x axis. When a uniform and vertical magnetic field acts on the loop B = Bu₂ with B = 2-10-2T, it rotates by an angle 0 = 30° Calculate the value of the current i and the work W done by the field on the loop during the rotation. R B

A rigid rectangular loop, with sides PQ = RS = a = 20 cm and QR = SP = b = 10 cm, has a mass per unit of length = 5-10-2g/cm and is crossed by a current i. It can rotate without friction around PQ which is parallel to the horizontal x axis. When a uniform and vertical magnetic field acts on the loop B = Bu₂ with B = 2-10-2T, it rotates by an angle 0 = 30° Calculate the value of the current i and the work W done by the field on the loop during the rotation. R B