Another Q:
What is the difference between a voltage vs time graph and a Current vs time graph? Assume initial position to be parallel to the field and an AC gen.
Rate of change of the radius
r is
.
=0.2-\frac{1}{2}t,$ $0\leq t\leq0.2)
(
r in metres)
So the area of the ring as a function of time is
=\pi r^2 (t)=\pi \left (0.2-\frac{1}{2}t\right ) ^2)
 = BA=2\pi \left (0.2-\frac{1}{2}t\right ) ^2)
(as magnetic field is a constant 2 T; units of the flux is T m
2)
 =-\frac{\mathrm{d\Phi} }{\mathrm{d} t})
(Lenz's Law)
 =2\pi\left ( 0.2 - \frac{1}{2}t \right )=\frac{2\pi}{5}-\pi t)
. So you sketch this straight line for
t from 0 to 0.2 s. (Units of the EMF is V (volts)). After 0.2 s, since the radius won't be changing then, the EMF will be 0.
