Electromagnetism – Faraday’s law

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The circuit shown is in a uniform magnetic field that is into the page and is decreasing in magnitude at rate of 150 tesla/second. The ammeter reads

A. 0.15 A
B. 0.35 A
C. 0.50 A
D. 0.65 A
E. 0.80 A

(GR9677 #02)

Solution:

IR − ɛ = 0
= (V − ɛ)/R

ɛ = − dΦ/dt = −AdB/dt

Given:
dB/dt = −150 t/s (minus sign because it’s decreasing)
A = (0.1 m)= 0.01 m2
R = 10 Ω
V = 5 V

ɛ = − (0.01)(−150) = 1.5 V
= (5 − 1.5)/10 = 3.5/10 = 0.35 A

Answer: B

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