• if the circuit is on series and you increase the voltage then you add two or more bulb, the brightness decreases.
• but if it's on parallel, even if you add two or more bulb as you increase the voltage, the brightness of the bulb remains the same or became brighter, because they were all independent in gaining current.
Answers & Comments
The bulb will become more brighter than usual
– ohm's law
higher the voltage the higher the amperes.
• if the circuit is on series and you increase the voltage then you add two or more bulb, the brightness decreases.
• but if it's on parallel, even if you add two or more bulb as you increase the voltage, the brightness of the bulb remains the same or became brighter, because they were all independent in gaining current.