Question

A well-made circular coil of wire consisting of 50 turns whose radius is 0.08 m, is made to spin about a diameter at a rate of 3 times every second. If the coil is placed a uniform magnetic field of field strength 0.21 T whose direction is perpendicular to the diameter, what is the peak emf induced in the coil?

A wire has a cross-sectional area of 1.8x10^-4 m² and a resistivity of 3.2x10^-8 ohm-meters. How long of a piece of this wire is needed to achieve a resistance of 6.0 ohms?

Answer 1

Solution :

Given :

N = 50

r = 0.08 m

f = 3 Hz

B = 0.21 T

Since: E_max = N B A = N B (r²) (2f) = (50)(0.21 T) ()(0.08 m)² (2)(3 Hz) = 3.979 V

.

.

Given :

A = 1.8 x 10^-4 m²

=3.2 x 10^-8 ohm-meters

R = 6.0 ohms

Since : R = L / A

Thus : L = R A / = (6.0 ohms)(1.8 x 10^-4 m²) / (3.2 x 10^-8 ohm-meters) = 33750 m