A loop of radius r=25 cm lies in a magnetic field of 0.57 T. The loop is perpendicular to the magnetic field. The loop is pulled by forces at points A and B, producing a loop of zero area in 0.0040 s. What is the average emf induced in the circuit?

Im really unsure how to start this problem, and also confused what it means by perpendicular, does that mean that the angle/theta is 90 degrees?
Any help is greatly appreciated!

Question

A loop of radius r=25 cm lies in a magnetic field of 0.57 T. The loop is perpendicular to the magnetic field. The loop is pulled by forces at points A and B, producing a loop of zero area in 0.0040 s. What is the average emf induced in the circuit?

Im really unsure how to start this problem, and also confused what it means by perpendicular, does that mean that the angle/theta is 90 degrees? 
Any help is greatly appreciated!

anonymous · Answer

The diagram is in the attachment!

anonymous · Answer

" loop is perpendicular to field " implies that plane of loop makes an angle of 90 with the direction of magnetic field.
As for finding the value of induced emf ,you need to know Faraday's law of electromagnetic induction.
It states that " magnitude of emf induced in closed loop is equal to rate of change of magnetic flux "
Now what is flux. It is the product of the area of the coil with perpendicular component of field to the area.

Flux=( Area of coil )  *  ( Component of field perpendicular to the plane of coil )

emf induced = change in flux / time taken
Find initial flux by simply multiplying the area of coil with the field strength.
Final flux is zero since the area of coil has been made zero.
The time taken for entire process is given.
Using all this, use the above relation to find emf.