Question

A solenoid with 300 loops of coil and a diameter of 5 cm is hooked up to a light bulb and is set up next to a strong magnet, which produces a field of strength 30 Tesla at the center of the solenoid. The solenoid is then spun. The light bulb has a resistance of 18 ohms. If the bulb requires a minimum current of 2.45 Amperes to light up, what is the maximum amount of time the solenoid can take to oscillate its surface area between 90 and 0 degrees to the magnetic field lines as it spins? Assume your answer is in units of seconds.

Answer 1

The emf generated in a solenoid when it is moved in a magnetic field is given by the formula

Since the resistance of the bulb is 18 Ohms and the minimum current required is 2.45 Amps, the voltage required will be

V = IR

V = 2.45 × 18

V = 44.1 Volts.

Also the area of the solenoid is

Now using the previous eqn and the voltage value,