Question

21. A lab tech is wearing a metal bracelet on her wrist, and she accidently brushes her wrist through an experimental set-up that has a 3.50T field with her arm pointing in the direction of the field. a. Find the average emf induced in the bracelet, given the bracelet's average diameter is 8.00 cm and assuming it takes 0.20 s to move it into the field. b. What current is induced in the ring if its resistance is 0.0150 12? c. What average power is dissipated? d. What amount of magnetic field is induced at the center of the bracelet? e. What is the direction of the induced magnetic field relative to the original field? f. Assuming the lab tech removes the bracelet back out of the field by completing the sweeping motion of her arm, what should occur as she brings her wrist and bracelet back out of the field?

Answer 1

a)

e = A B / t = pi/4 * 0.08^2* 3.5 / 0.2

e = 0.08792 V

b)

i = e/R = 0.08792 / 0.015 = 5.861 A

c)

P = ei = 0.5153 W

d)

B = (uo/4pi) 2 pi * i / r

B = 10^-7* 2* 3.14* 5.861 / 0.04

B = 9.2* 10^-5 T

e)

opposite to applied magnetic field

f)

net induced emf again goes off so current induced again goes to zero. also, as some value of energy dissipated through bracelet's resistance, a slight warmth can be observed in bracelet.

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