# The flexible loop in the figure below has a radius of 10.0 cm and is in a magnetic field of magnitude 0.160 T. The loop is grasped at points A and B and stretched until its area is nearly zero. If it takes 0.210 s to close the loop, what is the magnitude of the average induced emf in it during this time interval?

The flexible loop in the figure below has a radius of 10.0 cm and is in a magnetic field of magnitude 0.160 T. The loop is grasped at points A and B and stretched until its area is nearly zero. If it takes 0.210 s to close the loop, what is the magnitude of the average induced emf in it during this time interval?
mV

asked Feb 28, 2012 in Physics

According to Faraday's law of induction, emf induced in a loop is directly proportional to the time rate of change of magnetic flux through the loop:

so Emf = - change in magnetic flux / change in time

Magnetic Flux = integral of (magnetic field times change in Area)

So the change in magnetic flux is simply:

change in magnetic flux = Magnetic field * change in Area

Area = pi*r^2

r = 10 cm = 0.1 m

Area = pi*(0.1 m)^2

Magnetic field = 0.16 T

t = 0.21 s

substituting into the formula for Emf we get:

Emf = (0.16 T) *(pi*(0.1 m)^2) / (0.21 s)  = 0.0239 V  = 23.9 mV

answered Mar 3, 2012 by ~Expert~ (3,020 points)
selected Mar 3, 2012 by Joey33