A square loop of wire with resistance `R` is moved at constant speed `v` across a uniform magnet field confined to a square region whose sides are twice the lengths of those of the square loop

(a) Sketch a graph of the external forces `F` needed to move the loop at constant speed, as a function of to sketch a graph of the external force `F` need tho coordinate `x`, from`x=-2L` to `x=+2L`. (The coordinate `x` is measured from the centre of the oignetic field region to the centre of the loop. It is negative when the centre of the loop is to the left, of the centre of the magnetic field region. Take positive force to be to the right). (b) Sketch a graph of the induced current in the loop as a function of `x`. Take counterclockwise currents to be positive.

Answer

A

Explanation

Induced emf `(e=BvL)` and therefore induced curent is developed only during entering and during existing from the magnetic field.
`i=e/R=(BvL)/R`
`F=iLB=(B^2L^2v)/R`
Further magnetic force always opposes the change. Hence, external force is always positive. During entering into the field, `ox` magnetic field increases. Hence,induced current should produce `o.` magnetic field. Or it should be anti clockwise. During existing from the magnetic field case is just opposite.