A conducting bar is moved along a conducting U-Shaped track as shown in figure 1

Question

A conducting bar is moved along a conducting U-Shaped track as shown in figure 1. A uniform magnetic field exists and is directed into the page. The bar is moved along the track to the left at a constant speed. Calculate the direction of the induced current in circuit.

A conducting bar (1.2 meters) is moved along a conducting U-shaped track as shown in figure 1. A uniform magnetic field (3 telsa) exists and is directed into the page. Assume the resistance of the circuit is 15 ohms. Calculate the force required to move the bar along the track at a constant speed of 20 meters per second.

Explanation / Answer

1. The bar is moving to left
The flux into the page in the enclosed area is increasing
the induced current would resuce the flux into the page, i.e. increase flux out of the page
Hence direction of current = anticlockwise [ top to bottom in the rod]
2. Let current in the circuit be I
V = IR = emf induced = flux rate = d(BA)/dt = Blv
I = Blv/R
Force on a current carrying conductor = BIL = B(Blv)l/R = B^2l^2v/R = 9*1.2^2*20/15 = 17.28 N

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