In the figure above the coil is fixed in place and the magnet moves right to lef

Question

In the figure above the coil is fixed in place and the magnet moves right to left at a constant velocity v with the north and south poles labeled as shown.

i) What is the direction of the induced magnetic field in the coil? Explain your answer.

ii) What is the direction of the induced current in the resistor R as the magnet moves from right to left?

iii) The coil above has 7 turns. Each coil has a radius of 45 cm, and the resistor has a value of 5.0 ?. When the magnet moved the magnetic field changed from 0.300 ?T to 0.500 ?T in 2.80 s. How much current was produced in the coil?

Explanation / Answer

(i) from fardays law induced emf V = L(vxB)

From lenz law induced emf direction is oppose to magnetic filed direction

(ii) current is from left to right

(iii) N =7 , r =45 cm , R = 5ohm , B1 = 0.3 mT, B2 =0.5 mT , t =2.8 s

From faradays law induced emf V = -d(phi)/dt = NA(B1-B2)/t

V = (7*3.14*0.45*0.45*(0.3-0.5)*10^-3)/2.8

V = -0.318 mV

from ohms lae V = iR

i = 0.318/5 = -0.0636 mA

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