When two 60W light bulb branch circuits are wired in parallel, what happens when another parallel circuit is added?

When two 60W light bulbs are wired in parallel, each bulb operates independently and receives the full voltage supply from the source. This means that each bulb will have the same brightness when connected to the same voltage.

When an additional parallel circuit is added, it does not change the voltage across each existing bulb. The voltage remains constant for each branch in a parallel circuit, so the brightness of each bulb, including any new bulbs added in parallel, stays the same.

This is a fundamental characteristic of parallel circuits: voltage across each component is identical, which means that each component— in this case, each bulb—will exhibit the same brightness as others, assuming they are identical and connected to the same power source. Therefore, each bulb will maintain its brightness regardless of how many additional bulbs are added in parallel.