The light bulb in the circuit shown here has a resistance of

The light bulb in the circuit shown here has a resistance of 12 Ohm and consumes 5.0 W of power; the rod is 125 m long and moves to the left with a constant speed of 3.1 m/s. What is the strength of the magnetic field? What external force is required to maintain the rod\'s constant speed?

Solution

Here ,

R = 12 Ohm

P = 5 W

L = 1.25 m

v = 3.1 m/s

a) let the magnetic field is B

P = V^2/R

5 = (B * 3.1 * 1.25)^2/12

solving for B

B = 2 T

the magnitude of magnetic field is 2 T

b)

let the force is F

Power = F * v

5 = F * 3.1

F = 1.62 N

the force needed is 1.62 N