Tutorial 1
25) A rectangular coil, measuring \( 30 \mathrm{~cm} \) by \( 20 \mathrm{~cm} \) and having 40 turns, is rotated about an axis coinciding with one of its longer sides at a speed of \( 1500 \mathrm{r} / \mathrm{min} \) in a uniform magnetic field of flux density \( 0.075 \mathrm{~T} \). Find, from the first principles, an expression for the instantaneous emf induced in the coil, if the flux is at right angle to the axis of rotation. Evaluate this emf at an instant \( 0.002 \mathrm{~s} \) after the plane of the coil has been perpendicular to the field. (Ans: \( 28.27 \sin 157 \mathrm{t}, 8.74 \mathrm{~V}) \)