The figure below shows a conducting bar of length 20.0 cm that can move without

Question

The figure below shows a conducting bar of length 20.0 cm that can move without friction on a pair of conducting rails. The rails are joined at the left by a battery of emf 3.00 V, and a switch that is initially open. The bar, which is initially at rest, has a resistance 7.00 , and we will assume the resistance of all other parts of the circuit is negligible. The whole apparatus is in a uniform magnetic field, directed into the page, of magnitude 0.200 T. Both the rails and the magnetic field extend far to the left and right.

Determine the magnitude and direction of the following.

(a) the current in the circuit immediately after the switch is closed (Take counterclockwise to be the positive direction. Indicate the direction with the sign of your answer.)
____A

(b) the net force on the bar immediately after the switch is closed (Take the positive direction to be to the right. Indicate the direction with the sign of your answer.)
____ N

(c) the current in the circuit a long time after the switch is closed (By "a long time," we mean that enough time has passed for the bar to reach a terminal [constant] velocity. Take counterclockwise to be the positive direction. Indicate the direction with the sign of your answer.)
____ A

(d) the net force on the bar a long time after the switch is closed (Take the positive direction to be to the right. Indicate the direction with the sign of your answer.)
____ N

(e) the velocity of the bar a long time after the switch is closed (Take the positive direction to be to the right. Indicate the direction with the sign of your answer.)
____ m/s

Explanation / Answer

a.) - ve direction

I = V/R = 3/7 = 0.428 A

current is in clockwise direction as positive terminal of battery is in the direction of clockwise.

b.) Magnetic force = BiL

F = 0.2* 0.428* 0.2 = 0.01712 N ( + ve direction Right }

c.)0 A

d.)zero N

e.)induce emf = Blv

3 = 0.2*0.2 V

Velocity = 75 m/s (+ ve direction)

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