How is the brightness of a light bulb related to resistance?

To run at the same voltage, a higher wattage incandescent light bulb has a lower resistance than other bulbs having a lower wattage.

Ohm's Law (A = V / R) states that, at a given voltage, the lower the resistance of the bulb's filament is made, then the higher its current flow will be. Higher current means more energy, more heat, and more light.

A higher resistance filament restricts the current flow more, resulting in less current, less heat, and less light.

Because of the Power Law (W = V x A) bulbs designed to take the same wattage when running on different voltages must have higher or lower resistances than one another, dependent on the voltage, so as to get the right amount of current to produce the wattage required.

The symbols shown in the equations above are defined as follows:

V = Voltage (the electrical potential difference, measured in volts)

A = Amperes (the electrical current or charge flow rate, measured in amps which are defined as coulombs per second)

R = Resistance (the electrical resistance to current flow, measured in ohms)

W = Wattage (the electrical power consumed, measured in watts)