Voltage  across parallel resistances

Imagine now the set of ornamental light bulbs connected in parallel shown in the figure. This is the method used for outdoor holiday lighting, or for bright indoor lighting. It is easy to fix a parallel-wired string of holiday lights if one bulb should burn out than it is to fix a series-wired string. And failure of one bulb doesn't cause catastrophic system failure. Actually, it might be awhile before you notice that bulb is dark, as all the other ones will stay lit, and the brightness of them will not change.

Figure--   Light bulbs in parallel.

In a parallel circuit, the voltage across each component is always same and it is always equal to the supply or battery voltage. The current drawn by each component depends on the resistance of that particular device. In this sense, the components in a parallel-wired circuit work independently, as opposed to the series-wired circuit in which they all interact.

If any branch of a parallel circuit is taken away, the conditions in other branches will remain unchanged. If new branches are added, assuming the power supply can handle the load, conditions in earlier existing branches will not be affected.