*8.  Multiple-Concept Example 2 discusses the concepts that are used in this problem. Suppose that the magnetic field in Figure 22.5 has a magnitude of 1.2 T, the rod has a length of 0.90 m, and the hand keeps the rod moving to the right at a constant speed of 3.5 m/s. If the current in the circuit is 0.040 A, what is the average power being delivered to the circuit by the hand?

 

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Power delivered by the hand is equal to the power expended by the light, which is found from

 

We know the current, and we get the voltage because the voltage is equal to the emf induced across the rod.

 

 

 

 

Note one could calculate the work done by the hand using the mechanical relationship that

 

 

The force of the hand must be equal the magnetic force acting on the bar due to the movement of the conductor in the magnetic field.

 

Magnitude of this is

 

Angle is 90° as L is in the direction of the current which is perpendicular to B in the is case.

 

And

 

As we found before!

 

 

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This page last updated on June 23, 2018