A 30-turn coil 8 cm in diameter is in a magnetic field of 0.1 T that is parallel to its axis. a) What is the magnetic flux through the coil? b) In how much time should the field drop to zero to induce an average emf of 0.7 V in the coil? Thank you.

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Answer 1 · 2018-03-13T18:50:21

Given diameter of coil =#8 cm# so radius is #8/2 cm = 4/100 m#

So,magnetic flux #phi=BA=0.1*pi*(4/100)^2=5.03*10^-4 Wb#

Now,induced e.m.f #e=-N (delta phi)/(delta t)# where,#N# is the number of turn of a coil

Now, #delta phi =0-phi=-phi#

and, #N=30#

So, #t=(N phi)/e=(30*5.03*10^-4)/0.7=0.02156s#