A technician wearing a brass bracelet enclosing area 0.00500 m2 places her hand in a solenoid whose magnetic field is 4.50 T directed perpendicular to the plane of the bracelet. The electrical resistance around the circumference of the bracelet is 0.0200 . An unexpected power failure causes the field to drop to 1.35 T in a time of 20.0 ms. (a) Find the current induced in the bracelet.

39.375 A

Explanation:

To find the induced current, we use the relation

e = -ΔΦ/Δt, where

ΔΦ = change in magnetic flux of the bracelet

Δt = change in time, = 20 ms

Also, Φ = A.ΔB, such that

A = area of the bracelet, 0.005m²

ΔB = magnetic field strength of the bracelet = 1.35 - 4.5 = -3.15 T

ΔΦ = A.ΔB

ΔΦ = 0.005 * -3.15

ΔΦ = -.01575 wb

e = -ΔΦ/Δt

e = -0.01575 / 20*10^-3

e = 0.7875 V

From the question, the resistance of the bracelet is 0.02 ohm, so

From Ohms Law, I = V/R

I = 0.7875 / 0.02

I = 39.375 A

the working equation for the angular size is the product of the physical size and 360 degrees divided by the product of two pi and distance from earth. the minimum size would be 0.559 degrees while the maximum size would be 0.49 degrees.