A square loop of side 10 cm and resistance `0.5Omega` is placed vertically in the east-west plane. A uniform magnetic field of 0.10T is set up across the plane in the north-east direction. The magnetic field is decreased to zero' in 0.70 s at a steady rate. Determine the magnitudes of induced emf and current during this time interval.

Explanation

The angle `del` made by the area vector of the loop with the magnetic field is `45^(@)`. From eq. `phi_B=B.A.= BA cos theta` the initial magnetic flux is `phi=BA cos theta`
`=(0.1 xx 10^(-2))/(sqrt2)Wb`
Final flux, `phi_("min")=0`
The change is flux is brought about in 0.70s. From Eq. `epsi=(dphiB)/(dt)`, the magnittude of hte induced emf is given by
`epsi=(|DeltaphiB|)/(Deltat)=(|(phi-0)|)/(Deltat)=(10^(-3))/(sqrt2xx0.7)=1.0mV`
And the magnitude of the current is `I=epsi/R=(10^(-3)V)/(0.5Omega)=2mA`
Note that hte earth's magnetic field also produces a flux through the loop.