Emf Problem (1 Viewer)

[mathsfreak1010]

A two-turn circular wire loop of radius 0.5 m lies in a plane perpendicular to a uniform magnetic field of magnitude 0.4 T . Now the wire is reshaped from a two-turn circle to a one-turn circle in 0.1 s (while remaining in the
same plane). What is the magnitude of the average induced emf in the wire during this time?? ?


Help please, im seriously stuck on this question

THANKS IN ADVANCE

 

[mysterymarkplz]

I'm not quite sure but I think the emf induced is 0. using your e.m.f = -n(change in flux/ change in time), youve changed time and n but there is no change in radius of the loop or a change in magnetic field, flux = BA, since no change, then change in flux = 0, hence e.m.f should = 0 too. Could someone else check on this question? Haven't done phys in a while

 

[mathsfreak1010]

well thats what i initially thought as well however, my textbook says the answer is 6.28 V

 

[mysterymarkplz]

I know how they got the answer.
Since the radius is 0.5m, the area of the circle is TT x (0.5)^2
Fi = BA,
Fi = 0.4 x TT x (0.5)^2 = 0.314
If you put that into your lenz's law equation using n as 2 and change in t as 0.1 you should get 6.28 as the answer.
I guess any change in the loop whether it may be magnetic field, area or no. of turns should technically cause a change in flux since no. of turns and magnetic flux are proportional in some way.

 

[mathsfreak1010]

thank you so much