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Q6.4   A rectangular wire loop of sides 8 cm and 2cm  with a small cut is moving out of a region of uniform magnetic field of magnitude 0.3T directed normal to the loop. What is the emf developed across the cut if the velocity of the loop is 1 cm s^{-1} in a direction normal to the (a) longer side, (b) shorter side of the loop? For how long does the induced voltage last in each case?

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Given:

Length of rectangular loop :

l=8cm=0.08m

Width of the rectangular loop:

b=2cm=0.02m

Area of the rectangular loop:

A=l*b=(0.08)(0.02)m^2=16*10^{-4}m^2

Strength of the magnetic field

B=0.3T

The velocity of the loop :

v=1cm/s=0.01m/s

NOW,

a) Induced emf in long side wire of rectangle:

e=Blv=0.3*0.08*0.01=2.4*10^{-4}V

this emf will be induced till the loop gets out of the magnetic field, so 

time for which emf will induce :

t=\frac{distnce }{velocity}=\frac{b}{v}=\frac{2*10^{-2}}{0.01}=2s

Hence a 2.4*10^{-4}V emf will be induced for 2 seconds.

b) Induced emf when we move along the width of the rectangle:

e=Bbv=0.3*0.02*0.01=6*10^{-5}V

time for which emf will induce :

t=\frac{distnce }{velocity}=\frac{l}{v}=\frac{8*10^{-2}}{0.01}=8s

Hence a 6*10^{-5}V emf will induce for 8 seconds.

Posted by

Pankaj Sanodiya

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