AP EAPCET 08-Jul-2022 Shift 1 Paper

Average power loss in a rotating coil in 1 rotation is
Pavg=

emax.Imax

2

=

emax2

2R

=

(NBAω)2

2R

......(i)
Here, number of turns, N=40
Intensity of magnetic field, B=0.05T
Area of coil, A=0.01m2
Angular speed, ω=50rad∕s
Resistance of closed loop of coil,
Average power loss, Pavg=25mW
=25×10−3W
So, fromeq. (i) we have
25×10−3=

(40×0.05×0.01×50)2

2R

⇒ Resistance of coil,
R=

(40×0.0×0.01×50)2

2×25×10−3

=20Ω