A hand-held generator produces an EMF across the two leads when the handle is tu

Question

A hand-held generator produces an EMF across the two leads when the handle is turned, which causes a solenoid to rotate within a magnetic field produced by a small magnet. Consider the two scenarios shown in figures "a" and "d" below where the resistors represent light bulbs. In order to get the light bulbs in configuration "d" (two bulbs in parallel) to be the same brightness as that of configuration "a" in which the handle is being rotated at 20 cycles/minute, at what rate should the handle be rotated?

a

d

14 cycles/minute

40 cycles/minute

5 cycles/minute

20 cycles/minute

14 cycles/minute

40 cycles/minute

5 cycles/minute

20 cycles/minute

Explanation / Answer

As the resistances in the figure 'd' are parellel, the potential across the each resistor will be same and is equal to the potential across the single resistor in figure 'a' As there is same potential across each resistor (bulb), the brightness will be same. Therefore for the two bulbs to have the same brightness as that of the single bulb, same potential should be generated. So the lever should be turned as same in case of the single resistor Therefore the handle should be rotated at a rate of 20 cycles/minute OPtion 'd' is right choice

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