Acoil with circular cross section and 18 turns is rotating at a rate of 370 rpm (revolutions per minute) between the poles of a magnet. if the magnetic field strength is 0.7 t and peak voltage is 0.7 v, what is the radius of the coil (in cm)?

r= 2.1 cm

Explanation:

Given that

N= 18 turns

N= 370 rpm

B= 0.7 T

V= 0.7 V

The flux given as

Φ = B N A cosωt

B=Magnetic filed

N==Number of turns

A=Area

ω=Speed

t= time

The voltage V give as

Φ = B N A cosωt

V= BNA ω sinωt

The maximum value of voltage

V(max)= BNA ω

We know that ω=2 πf

ω = 38.74 rad/s

A=π r²

V(max)= BNA ω

0.7 = 0.7 x 18 x π r² x 38.74

r²=4.56 x 10⁻⁴ m²

r=0.021 m

r= 2.1 cm

the answer is b ) square root of 5