A lightbulb glows brightly when it is connected across a certain battery. The battery will maintain a constant potential difference even as its output current increases. Four more identical bulbs are then connected across the same battery, so that all five bulbs are in parallel. How does the brightness of each of the five bulbs in parallel compare to the original bulb?

The brightness will remain the same .

Explanation:

Th current through each bulb will remain the same in both the cases because the voltage that each bulb is getting in both the cases will be same .

If V be the emf of the battery . In the first case current through one bulb

= V / r where r is resistance of the bulb .

In the second case , as the bulbs are in parallel , each of them will get full potential of the battery so in this case current through each bulb

= V / r .

So brightness of each bulb will remain same as current will remain the same.