A Light Bulb and Resistance: How Does Resistance Affect Brightness?

A light bulb and resistance

A light bulb is basically a resistor that gets so hot that it glows, emitting light. For this tutorial, we will assume the resistor in the light bulb is ohmic (that means Ohm's law applies to the resistor). The rate of energy emitted by the light bulb is its output power, commonly referred to as luminosity (brighter means more luminous). Hook up a light bulb to a 5-V battery. Right-click (or control-click) on the light bulb, and change its resistance.

How does brightness depend on resistance?

A. The brightness of the light bulb is independent of its resistance. It only depends on the voltage of the battery.
B. The light bulb gets brighter as the resistance is increased.
C. The light bulb gets dimmer as the resistance is increased.

Final answer:

The brightness of a light bulb decreases as its resistance increases when connected to a constant voltage source, due to less current flowing through the bulb, leading to less power dissipation. So the correct option is C.

Explanation:

The brightness of a light bulb, often referred to as its luminosity, depends on the power it dissipates, which is related to the resistance in the bulb. According to Ohm's law, increasing the resistance while keeping the voltage constant results in a lower current through the bulb. This can be seen in the equation P = I^2 * R, where P is the power, I is the current, and R is the resistance. If the voltage (V) is kept constant and resistance (R) is increased, the current (I) will decrease since I = V/R. Consequently, the power dissipated by the bulb which determines its brightness will decrease as less current flows through it. Therefore, the light bulb gets dimmer as the resistance is increased.