4. A rectangular coil of N turns has width W and length L. It moves withvelocity

Question

4. A rectangular coil of N turns has width W and length L. It moves withvelocity v as it enters a region of uniform magnetic field Bstatic (see figureat below). The coil has resistance R and mass M. (a) In what direction doesthe induced current circulate in the coil when it enters the magnetic field?(b) What is the magnitude of the induced EMF and current in the coil? (c)While there is an induced current in the coil, what is the direction of theforce exerted by Bstatic on the bottom side of the coil? (d) While there is aninduced current in the coil, what is the magnitude of the force exerted byBstatic on the bottom side of the coil? (e) What would be your answer topart 3(c) (direction of the force) if Bstatic was reversed, i.e., into the pagerather than out of it? Explain.

Explanation / Answer

(a) According to lenz law current induce in CLOCKWISE direction.

As coil enters in the Bstatic an outward field lines are increasing in coil so according to lenz law it resist it and induce a current in clockwise direction which produce inwards field lines.

(b) as 1st wire is enters e = B L v

I = e / R = B L v / R

(c) By left hand rule on bottom side an UPWARD force is exerted on wire.

(d) F = I L B = (B L v / R) L B = B^2 L^2 v / R

(e) DIrection of force remains same (UPWARD) because the direction of induce current also reversed.

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