Question

A circular coil with a radius of 0.29 meters is wrapped 752 times and is spun in a magnetic field of 0.22 milli-tesla. It is then connected to the primary side of a transformer with 68 windings on the primary side. The secondary side has 25 windings. If the resistance of the secondary side of the transformer is 7 Ohms. At what frequency, in Hertz, does the coil need to be spun in the field if the maximum current on the secondary side of the transformer is 8 amps?

Answer 1

no of turns, N=752

radius, r=0.29 m

B=0.22 mT

no of coils in primary side, Np=68

no of coils in secondary side, Ns=25

resistance of the secondary coil, Rs=7 ohms

current on the secondary side of the transformer, Is=8A

use,

voltage on secondary side, vs=Is*Rs

vs=8*7

vs=56 v

and

vp/vs=Np/Ns

vp/56 = 68/25

vp=152.32 v

voltage in primary coil is, Vp=152.32 v

use,

emf=N*B*A*w

vp=N*B*(pi*r^2)*w

152.32=752*0.22*10^-3*(pi*0.29^2)*(2pi*f)

===> f=554.614 Hz

frequency f=554.614 Hz