A conducting bar of length 0.3 m can move without friction on a pair of conducti

Question

A conducting bar of length 0.3 m 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, initially at rest, has a resistance 9.00 Omega (resistance of all other parts of the circuit is negligible). The whole apparatus is in a uniform magnetic field of magnitude 0.100 T directed into the page. Both the rails and the magnetic field extend far to the left and right. WHAT IS THE SPEED OF THE BAR A LONG TIME AFTER THE SWITCH IS CLOSED? The answer is 100 m/s. Please provide an explanation for this answer.

Explanation / Answer

When switch is closed bar moves right with increasing velocty due the magnetic force on it.

the bar moves so long as the induced emf on the bar equals E . when it reaches E no more current flows throught he circuit and the bar moves with that same velocity.

lenz law gives e= B*L*V =E

V= E/BL = 3/0.3*0.1 = 100 m/s

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