As shown in the figure below, a coil that is square, has 30 turns, is 0.82 , and

Question

As shown in the figure below, a coil that is square, has 30 turns, is 0.82 , and is 10.0 cm on a side is between the poles of a large electromagnet that produces a constant, uniform magnetic field of 0.7 T directed into the page. As suggested by the figure, the field drops sharply to zero at the edges of the magnet. The coil moves to the right at a constant velocity of 3.00 cm/s. What is the current through the coil wire in the following instances?

(a) before the coil reaches the edge of the field
A

(b) while the coil is leaving the field
A

(c) after the coil leaves the field
A

(d) What is the total charge that flows past a given point in the coil as it leaves the field?
C

Explanation / Answer

flux = N*B*A

A = l^2

induced emf = E = rate of change in flux

current i = E/R

(a) before the coil reaches the edge of the field

change in flux = 0

E = 0
I = 0

(b) while the coil is leaving the field

change in flux = N*(B2-B1)*A

emf = E = -rate of chage in flux

E = N*(B2-B1)*l*l/t = N*(B2-B1)*l*v

i = E/R

i = (30*0.7*0.1*0.03)/0.82

i = 0.077 A <<<<<---------------answer

(c) after the coil leaves the field

out side B = 0

i = 0

(d) What is the total charge that flows past a given point in the coil as it leaves the field?

Q = i*t = i*l/v = 0.26 C    

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