Question

A flashlight can be made that is powered by the induced current from a magnet moving through a coil of wire. The coil and magnet are inside a plastic tube that can be shaken causing the magnet to move back and forth through the coil. Assume the magnet has a maximum field strength of 0.05 T. Assume that the radius of the coil is 1.5 cm and the magnet is shaken with a frequency of about two shakes per second. Specify the the number of turns necessary to light a standard 1-watt, 3-V flashlight bulb.

Answer 1

n = 4.25 x 10⁴ .

Step-by-step explanation:

EMF required to be produced = 3 V .

Let n be the required no of turns .

rate of change of flux = n x B x A x f where n is no of turns of coil , B is magnetic field , A is area of coil and f is frequency of change .

B = .05 T , A = π x (.015)² = 7.065 x 10⁻⁴ m² , f = 2

emf induced = rate of change of flux

= n x .05 T x 7.065 x 10⁻⁴ m² x 2

= .7065 x 10⁴ x n

Given

.7065 x 10⁻⁴ x n = 3

n = 4.25 x 10⁴ .