I performed an experiment to compare the power dropped on a combination of a motor (small fan) and a lamp. I got the motor and a lamp from a lab, they are very old and all labels on the elements are gone. I connect them to a 3 V battery in both serial and parallel circuit as follows:
In the top circuit, when the fan is spinning in full speed, I see that the lamp is very dim until I slow down the fan. In the bottom circuit, the brightness of the lamp will not be affected by the fan. I am trying to analyze this two situation in the following statements.
In the serial circuit, the voltage drop on motor and lamp add up to 3 V, but the current on both elements are the same. I am guessing the resistance of the lamp is much smaller than that of the motor so the voltage drop on the motor dominate. Most power is drop on the motor; I think that's the reason why the lamp is so dim. But what I don't understand is why the lamp becomes so bright if I hold the motor to stop the fan. Will stopping the fan cause the voltage drop on the motor?
In the parallel case, the voltage drop on lamp and motor are same. I know the current are different on elements. But in the case of using a battery as the power supplier, how is the current output determined?
I am thinking the total current output from the battery depends on the lamp and motor, in each path, the current is provided so to satisfy the power of the element. So it will try to output enough total current for each element to make the lamp bright and the fan spin fast. Is this correct?