A loop of wire of radius a = 50. mm has an electrical resistance R = 0.031 ? . T

Question

A loop of wire of radius a = 50. mm has an electrical resistance R = 0.031 ? . The loop is initially inside a uniform magnetic field of magnitude B0 = 1.3 T parallel to the loop's axis. The magnetic field is then reduced slowly at a constant rate, which induces a current I = 0.20 A in the loop. How long does it take for the magnitude of the uniform magnetic field to drop from 1.3 T to zero?

Part B: What is the direction of the induced current in the wire shown in the picture?

A. Clockwise

B. Counterclockwise

* I AM MOST CONCERNED FOR THE ANSWER FOR PART B. IS IT CLOCKWISE OR COUNTERCLOCKWISE?*

Explanation / Answer

The induced current I = induced emf/R = /R where = / t = A*B/t
So I = A*B/t/R

therefore B/t = A*/(R*I) = *r^2/(R*I) = *(50x10^-3m)^2/(0.031*0.20A) = 1.266T/s
to reduce B from 1.3 to 0 would take (1.3-0)/1.266=1.3/1.266 = 1.027 s

B The direction of current opposes the decrease of B into the page, and thus must act to increase B into the page. From the right-hand rule, this corresponds to a clockwise current

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