A coil is placed perpendicular to a magnetic field of 5000 T. When the field is changed to 3000 T in 2 s, an induced emf of 22 V is produced in the coil. If the diameter of the coil is 0.02 m, then the number of turns in the coil is:
(2) 70
Faraday's law: | |=N t=N ( B)A t
A= r2= (0.01)2= 10-4 m2, B=2000 T
22=N 2000 10-42=N 0.1
N= 220.1 227=70
Answer: (2)
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