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Q.
A magnetic flux of 500 $ \mu $ Wb passing through a 200 turns coil. is reversed in $ 20\times {{10}^{-3}} $ seconds. The average emf induced in the coil in volts, is:
EAMCETEAMCET 2004
Solution:
The induced emf in the coil is $ e=-N\left( \frac{d\text{o }\!\!|\!\!\text{ }}{dt} \right) $ Given $ d\text{o }\!\!|\!\!\text{ =}\,\text{o}{{\text{ }\!\!|\!\!\text{ }}_{2}}-\text{o}{{\text{ }\!\!|\!\!\text{ }}_{1}}=2\times 500\mu \,\,Wb $ $ dt=20\times {{10}^{-3}}\sec $ $ N=200 $ $ e=-N\left( \frac{\text{o}{{\text{ }\!\!|\!\!\text{ }}_{2}}-\text{o}{{\text{ }\!\!|\!\!\text{ }}_{1}}}{dt} \right) $ Putting the given values in Eq. (i) $ e=-\frac{200\times 2\times 500\times {{10}^{-6}}}{20\times {{10}^{-3}}} $ $ =-10\,\text{volt } $ $ \Rightarrow $ $ |e|=10\,\text{volt} $