Question

why is resistance useful in lightbulbs? it allows the filament to heat up and glow. it allows the filament to cool off and glow. it allows the filament to heat up and get dim. it allows the filament to cool off and get dim.

Explanation:

When current passes through a lightbulb's filament, due to the filament's resistance, electrical energy is converted into heat energy (based on the principle \(P = I^{2}R\), where \(P\) is power, \(I\) is current, and \(R\) is resistance). As the filament heats up (not cools off), it reaches a high temperature and starts to glow (emitting light). A dim filament would not be a useful outcome for a lightbulb's purpose of providing illumination.

Answer:

It allows the filament to heat up and glow.