A square loop of side 10 cm and resistance 0.70 ohm is placed vertically in the east -west plane. A uniform magnetic field of 0.10 T is set up across the plane in north-east direction. The magnetic field is decreased to zero in 0.7 sec. at a steady rate. Determine the magnitudes of induced e.m.f. and current during this time interval.

Explanation

Here,
`A = (10 cm)^(2) = 100 cm^(2) = 10^(-2) m^(2)`
`R = 0.70 ohm, B_(1) = 0.10 T, theta = 40^(@)`
`B_(2) = 0, dt = 0.7 s, e = ?, I = ?`
Initial flux, `phi_(1) = B_(1) A cos theta`
`= 0.10 xx 10^(-2) cos 45^(@) = (10^(-3))/(sqrt2)Wb`
Final flux, `phi_(2) = 0` `( :' B_(2) = 0)`
`e = (|d phi|)/(dt) = (|phi_(2) - phi_(1)|)/(dt) = (10)/(sqrt2 xx 0.7) = 10^(-3) V`
`I = (e)/(R ) = (10^(-3))/(0.7) = 1.4 xx 10^(-3) A`