Acircular loop 40 cm in diameter is made froma flexible conductor and lies at right angles to a uniform 12-t magnetic field. at time t = 0 the loop starts to expand, its radius increasing at the rate of 5.0 mm/s find the induced emf in the loop: a) at t 1.0 s and b) at t 10 s.

Explanation:

As we know that magnetic flux is given by

now from Faraday's law

now we have

B = 12 T

Part a)

now at t = 1 s

r = 20 + 0.5 = 20.5 cm

Part b)

now at t = 10 s

r = 20 + 0.5(10) = 25 cm

one "light year" is the distance that light travels, through vacuum, in one julian year.   that's 365.25 days, of 24 hours each.