NOTE: I DO NOT WANT YAHOO ANSWERS OR PHYSICS FORUMS ANSWERS The drawing below sh

Question

NOTE: I DO NOT WANT YAHOO ANSWERS OR PHYSICS FORUMS ANSWERS

The drawing below shows a circular loop of wire (radius 0.15 m) connected to a power supply. The top loop is directly over the bottom loop, which is not connected to anything.

A. When the switch is first turned on, in which direction will the current first flow in the

bottom loop?

B. The bottom coil receives a constant magnetic field of 0.8 T from the top coil and

starts spinning perpendicular to its original plane at a speed of two revolutions per

second. Find the average emf induced in that coil as it rotates through one

Explanation / Answer

A)

If we observed from the top of the top loop, when whitch is turned on, current flows in clockwise direction. This produces magnetic field in the loop directed downwards(given by Right Hand thunb rule). This downward directed field induces current in the bottom loop such that it opposes the magnetic field from the top loop(Lenz's Law). Thus induced magnetic field in the bottom loop must be directed upwards.So, induced current in the lower loop must be in counter-clockwise direction(given by Right hand thumb rule).

B)

average induced emf is given by:

E = NBAW

where N = number of turns = 1

B = magnetic field = 0.8 T

A =area of the loop = pi*r^2 = 3.14*0.15^2

W = angular speed of rotation = 2 rev/s = 2*2*pi rad/s = 2*2*3.14 rad/s

So, E = 1*0.8*3.14*0.15^2*2*2*3.14 = 0.71 V <-------------answer

C)

By the above reasoning the current must be counter-clockwise

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