A square loop of side l being moved towards right at a constant speed v as shown in figure. The front edge enters the magnetic field B at t = 0. The width of field is 4l. Sketch induced emf versus time graph.

Explanation

From, t = 0 to `t=(l)/(v)`
Induced emf,
e = Bvl and `I=(e)/(R)=(Bvl)/(R)`, which is anti-clockwise in direction.
Again from `t=(l)/(v)` to `t=(4l)/(v)`, emf e = 0
`t=(4l)/(v)` to `t=(5l)/(v)"emf e"=Bvl`
So, induced current `I=(e)/(R)=(Bvl)/(R)`, which is clockwise in direction now.
So, the plot of induced emf versus time is given as