2) A 0.3 kg bar slides vertically down a set of rails at a terminal speed v whil

Question

2) A 0.3 kg bar slides vertically down a set of rails at a terminal speed v while a 1.24 m section of the bar is immersed in a uniform magnetic field of magnitude 0.4 T directed horizontally ( out of the page). The resistance of the bar is 0.2 2. The rails have negligible resistance. 1.24 m a) Determine v b) In which direction does the induced current flow? Be specific and explain how you know c) Compare, through calculation, the amount of work done on the bar by gravity to the thermal (internal) energy generated in the bar and the rails as the bar falls 0.5 m.

Explanation / Answer

in case of terminal speed net force on bar = 0

BIL = mg ( magnetic force = gravitational force)

B*(vBL/R)*L = mg ( I = vBL/R)

vB^2*L^2/R = mg

=> v*(0.4)^2*(1.24)^2 = 0.3*9.8*0.2

=> v = 2.39 m/s

induced force will act in opposite direction to mg

=> it must be in anticlock wise direction

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