Light Bulbs: Watts & Voltage

Instructor: Catherine Maher

Catherine has taught 4th through 7th grade and has a master's degree in reading education.

In this lesson, you will learn what volts and watts mean, especially when used to describe a type of light bulb. You will also review what is meant by an electrical current.

Lights Out!

You walk into a room and flip a light switch. With a quiet 'pop', the light goes on and then burns out. You need a new light bulb!

If you look at a store display of light bulbs, you'll see dozens of shapes, sizes, and colors. Almost all of them will have a printed description about the voltage and wattage of each particular bulb. But what do 'voltage' and 'wattage' mean?

How do you know what voltage and wattage mean on a bulb?
Image of many light bulbs

Electrical Units

Electricians use several measurements of electrical power: voltage and wattage. Electricity is the flow of electrons in a current through a conductor like a wire. Electrons are very tiny, and we can't see them flow. But the idea of a current is one you might already be familiar with: a current of water flowing through pipes. This comparison can help you understand voltage and wattage.


One way we can measure electricity is with voltage, or volts, which measure the force of electricity moving through a current. Imagine a small pump pushing water through a pipe. If you replace the small pump with a large pump, you'll increase the water force. In the same way, a large battery has more volts, or force, of electricity than a small one.


Electricians also use wattage, or watts, a measurement of the power of an electric current. Think of watts as a measurement of the work that a particular current can do, like lighting a light bulb. Imagine a flow of water turning a water wheel. A powerful flow of water will turn the wheel fast, just like many watts will produce a bright light.

You can compare the current of electricity to the flow of water. The water can turn the wheel, and the electricity can light a bulb.
image of water flowing onto a water wheel

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