PHY Electromagnetic Induction

2012-01-25 5:01 am

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I have attempted to tackle this question before and I calculated v = 3.72m/s, which is the square root of the answer provided by my teacher, that is 13.86m/s. Could you please teach me how to calculate the answer?

回答 (1)

天同

2012-01-25 8:01 am

✔ 最佳答案

Consider a time interval of 1 s after the bas has attained terminal velocity v.
Magnetic flux change = (v.L).B.cos(45)
Induced emf = (v.L).B.cos(45)
Hence, current through the bar I = induced emf/resistance = (v.L).B.cos(45)/R
Magnetic force acting on the bar = (B.cos(45)).L.I
= [B.cos(45)]^2.L^2.v/R

Since at terminal velocity, the magnetic force equals to the weight component down the inclined plane.
i.e. [B.cos(45)]^2.L^2.v/R = mg.sin(45)
v = [mg.tan(45).R]/[B^2.L^2.cos(45)] = (1 x 9.8 x tan(45))/(1^2 x 1^2 x cos(45)) m/s
= 13.86 m/s

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