An electromagnet produces a uniform magnetic field of |B| = 1.70T over a cross-s

Question

An electromagnet produces a uniform magnetic field of |B| = 1.70T over a cross-sectional area of A = 0.230m2. A coil with N = 210 turns and a total resistance of R = 20.00 ohm is placed around the electromagnet. The current in the electromagnet is then smoothly reduced until it reaches zero. What is the magnitude of the induced current when the time it takes to completely reduce the magnetic field is (a) t = 22.0ms. (b) What is the magnitude of the induced current, if instead, it takes t = 14.0ms?

Explanation / Answer

flux = B*A = 1.7*0.23 = 0.391

d(flux)/dt = EMF

EMF = 0.391/0.022 = 17.77 V

I = 17.77/20 = 0.889A

b) EMF = 0.391/0.014 = 27.93 V

I = 1.4A

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