A conducting circular loop is rotated about its diameter at a constant angular speed of 100 rad/s in a magnetic field of 0.5 T perpendicular to the axis of rotation. When the loop is rotated by 30 from the horizontal position, the induced EMF is 15.4 mV. The radius of the loop is mm. (Take = 227)
Answer
14
Solution
In the horizontal position the field is along the normal to the loop (maximum flux, zero EMF). After turning through = t:
= BA t e = - d dt = BA t
At t = 30 : e = B( r2) 30
15.4 10-3 = 0.5 227r2 100 12
r2 = 15.4 10-3 725 22 = 1.96 10-4 m2
r = 1.4 10-2 m
r = 14 mm
Answer: 14