Physics – 4.2.2 Electric current | e-Consult

The light bulb connected to the a.c. power supply appears brighter because the electrons in the light bulb are being repeatedly pushed and pulled by the changing direction of the current. This repeated movement causes the filament in the light bulb to heat up more rapidly and to a higher temperature.

In a d.c. circuit, the electrons flow in a constant direction, resulting in a more steady heating of the filament. While the voltage is the same, the alternating nature of the current in the a.c. circuit means the filament is being heated more frequently, leading to a higher overall brightness. Essentially, the a.c. current is delivering energy to the filament more effectively due to the repeated changes in direction.