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What will happen when we connect two voltage sources in parallel combination? What if the voltage ratings of both sources are different?


If you connect two voltage sources in parallel, the little bit of resistance within each voltage source and the tiny resistances of the wires will serve as a very small resistance. Each voltage source would be more like a voltage source in series with a tiny resistor. If the voltage sources do not match, at least one will have a huge current. In most cases, both voltage sources will have huge currents in opposite directions. The voltages across the tiny resistances will balance out the two unequal parallel voltages.

Doing this will produce extreme currents within the sources, causing the sources to overheat. It is this sort of thing that can destroy a battery. A very simple example is a series circuit composed of two unequal voltage sources in opposite directions and a very small resistance. Consider 9 volt, 1.5 volt, and 0.2 ohms. You would end up with more than 35 amperes, for a short time. The heat would destroy the batteries.

Dr. Ken Mellendorf

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