Power and Light
Ever been curious about how power flows through a light bulb? In this experiment we will explore the basic concepts of how power creates light. Connect it yourself and find out!
- 3 Alkaline AA Batteries
- 1 Three Battery Holder
- 2 Single Battery Holders
- 2 Miniature 5-volt Light Bulbs
- 2 Red Alligator Wires
- 2 Black Alligator Wires
- 3 Green Alligator Wires
Experiment 1: Power and Light
Install a battery in the holder with the negative end against the spring. The two pins at the back connect with positive and negative ends of the battery.
Connect the battery to the light bulb using two alligator wires. The bulb glows very dimly.
The light bulb glows more brightly when you add a second battery.
The battery and the light bulb are components. When you connect them, you create a circuit. Imagine electricity flowing from the positive end of the battery, through the red wire, through the bulb, and back through the black wire to the negative end of the battery.
Those Tiny Pins
What Is Electricity?
Electricity consists of tiny particles in the wires, known as electrons. They have a negative charge, but when Benjamin Franklin was experimenting with electricity (before he got his picture on the $100 bill) he decided that electricity flows from positive to negative, and we still think of it that way.
The flow of electrons during a period of time is called current.
Your three-battery holder has positive and negative pins at the back.
Adding a third battery gives you a total of 4.5 volts. Now the light bulb glows even more brightly.
The electrical pressure created by a battery is called voltage and is measured in volts, abbreviated with letter V. A single AA battery is rated at 1.5V. When you connect its positive output to the negative end of a second battery, they are in series, and their voltages add up.
NOTE: If you added a fourth battery to get a total of 6V, the light would be brighter still — but might burn out after a short time, because it is designed for a maximum of 5V. All projects in this workshop can be powered with 4.5V.
The batteries in the holder don’t look as if they are in series, but they are, because the holder contains a hidden wire. Electricity doesn’t care if it follows a zig-zag path.
What happens if you make a circuit where two or three batteries are beside each other? Now the batteries are in parallel, and their voltages don’t add up anymore. You can connect any number of them in parallel, and you’ll still get just 1.5V.
Two batteries in parallel should last twice as long as a single battery, because they are sharing the work.
Try adding another light bulb beside the first. Now the bulbs are in parallel.
Each of the two bulbs in parallel will be as bright as when you had just one.
When two identical components are in parallel, electricity now has a choice of two paths from positive to negative, so the current doubles, and the batteries will only last half as long.
Move the light bulbs so that one follows the other. Hold them together with your finger and thumb. The bulbs are now in series.
Each of the bulbs in series will be less bright than before. The first will take half the voltage, and the second will take the other half.
When two identical components are in series, they create twice as much resistance for the current. Consequently, there will be half as much current, and the batteries will last twice as long.
Current is measured in amperes, abbreviated as amps. It is represented with letter A. Small currents are measured in milliamperes, abbreviated as milliamps, represented with mA. There are 1,000 milliamps in 1 amp (that is, 1,000mA = 1A).
You can think of volts as measuring the pressure that forces electrons into a wire, while the flow of electrons per second through the wire is measured in amps.
A diagram that shows how components are connected is called a schematic. Above are the schematic symbols for an incandescent bulb and two batteries.
Can you draw schematics of all the circuits that you have built so far?
Save Your Batteries
THINK ON THIS
How Did It Work?
When you connected power to the light bulb, it took just a moment to react. It was warming up. This kind of light contains a thin piece of wire, called a filament, which is heated by electricity flowing through it. The heat makes it glow.
Any object that gives off light as a result of heat can be described as incandescent. So, you have been playing with an incandescent light bulb.
Incandescent lights are not used so often in houses and offices anymore. We use fluorescent lamps or LEDs. I’ll get to LEDs later.