1.

A circular loop of radius R is placed in the uniform magnetic field. The value of magnetic field changes is given by equation B=B_0 e^(-t/tau) . Where B_0 and tau are constants. The emf induced in the coil is ____

Answer»

`pi^2B_0 E^(-t/tau) xx 10^(-2)` V
`(piR^2B_0)/tau e^(-t/tau)`
`pi^2B_0 tau e^(-t/tau)`
None of these

Solution :`phi=AB=pir^2B_0 e^(-t/tau)`
`THEREFORE epsilon=-(dphi)/(DT)`
`=-d/(dt)[pir^2B_0 e^(-t/tau)]`
`therefore epsilon=-piR^2B_0 d/(dt)(e^(-t/tau))`
`=-piR^2B_0 (-1/tau.e^(-t/tau))`
`therefore epsilon=(piR^2B_0)/tau e^(-t/tau)`


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