In: Physics
A circular wire loop of radius 1.4 cm is placed in a magnetic field of magnitude 2.3 T. If the magnetic field goes to zero in a time of 5 s, what is the magnitude of the current induced in the loop? The wire has a diameter of 2 mm, and the resistivity of copper is 1.7 x 10-8 Ohm-m.
According to Lenz's law, the voltage induced in the loop, V =
d/dt
is the flux
passing through the coil, = B x Area
of the loop
B = 2.3 T
A1 = R2 =
x (0.014)2 = 6.157 x 10-4
m2.
= BA1 =
1.416 x 10-3.
B becomes zero in 5 seconds, dt = 5 s
V = d/dt = 2.832 x
10-4 V
According to Ohm's law, V = IR
R = L/A
= 1.7 x
10-8 Ohm-m.
L = 2R = 0.028 m.
A2 = r2 =
x (1 x 10-3)2 = x 10-6
m2.
R = 4.76 x 10-4 Ohm
I = V/R = 2.832 x 10-4 V / 4.76 x 10-4 Ohm = 0.595 A