Will three bulbs connected in parallel glow brighter than two bulbs in parallel? The question is simple but i have not heard anything like this before. This was asked by my teacher in the viva of my electrical workshop class. And she said the three bulbs will glow brighter and i had to tell the reason for this. Now was this a trick question or is this true? Cause i clearly said ma'am there will be no difference. I want to know the truth before the finals please help. Cause i cannot find a reason for the bulbs to glow brighter the voltage is same and the current will be divided among three bulbs now so why would they glow brighter?
 A: There's a simple way to tell who's right: build the circuit and see what happens. Nature doesn't care about people's opinions, and She, by definition, will give you the right answer!
But you are correct: full marks on this one! If the three bulbs are connected in parallel across a voltage source, the voltage across them theoretically stays the same as when one bulb is connected across the same source.
The difference between the two situations is that, in the three bulb case, the total current drawn from the voltage source is tripled. This is what I think your teacher may be thinking of.
Practically, you will find that the bulbs will be slightly dimmer in the three bulb case as opposed to the one bulb case. This is because all practical voltage sources have a nonzero source impedance (also called "internal impedance" or "output impedance"), which means that they look like a voltage source in series with a resistance (in a DC circuit case). So, as the current increases to cope with the three bulb case, the voltage drop across the source impedance roughly triples, leading to a lower voltage across the parallel light bulbs.
