A metal bar is pulled to the right perpendicular to a uniform magnetic field. Th

Question

A metal bar is pulled to the right perpendicular to a uniform magnetic field. The bar rides on parallel metal rails connected through a resistor, as shown in the figure , so the apparatus makes a complete circuit.

1.Find the direction of the current induced in the circuit by looking at the magnetic force on the charges in the moving bar . [The current induced in the circuit is clockwise, counterclockwise, or 0.]

2. Explain your reasonings in part 1.

3.Find the direction of the current induced in the circuit by using Lenz's law. [The current induced in the circuit is clockwise, counterclockwise, or 0.]

4. Explain your reasonings in part 3.

Explanation / Answer

1. current is induced counter-clockwise. 2. we know, due to motion of the rod to the right, the electrons are accelerated towards down (ie from a to b). so,electrons move clockwise. as current is defined to the rate of change of +ve charge, current is in anti clockwise direction 3. anti clockwise direction 4. as the rod moves towards right , we observe the area formed by the loop comprising of the resistance R and the rod a-b, is increasing, so, as per Lenz's law, current is induced in such a direction, so as to oppose the change of flux, therefore current must be induced in such a direction so as to decrease the flux, so current must flow in counter clockwise direction(given by right hand thumb rule)

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