Q. When a circular coil of radius 1 m and 100 turns is rotated in a horizontal uniform magnetic field, the peak value of emf induced is 100 V. the coil is unwound and then rewound into a circular coil of radius 2 m. If it is rotated now, with the same speed, under similar conditions, the new peak value of emf developed is
A) 50 V
B) 25 V
C) 100 V
D) 200 V
Explanation
(d) Induced EMF=$\frac{N\mathrm{\Delta}\phi}{\Delta t}$
Peak value =$NBA\omega = 100V$ …(i)
Here $\ \ 2\pi r_{1} \times 100 = 2\pi r_{2} \times N_{2}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ N_{2} = \frac{r_{1} \times 100}{r_{2}} = \frac{1 \times 100}{2} = 50$
Now $\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ e_{0} = \frac{N}{2} \times B \times 4A \times \omega = 200V.$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.