- A 9-Volt battery
- A light-emitting diode (LED)
- Two wires
- A piece of cardboard
Instructions:
1. Cut the piece of cardboard into a rectangle about 2 inches by 4 inches.
2. Make a small hole in the center of the cardboard.
3. Connect one end of each of the wires to the terminals of the battery.
4. Connect the other end of one of the wires to the positive terminal of the LED.
5. Connect the other end of the second wire to the negative terminal of the LED.
6. Push the LED through the hole in the cardboard so that the light is on the side of the cardboard.
How it works:
When the battery is connected to the LED, the current flows through the wire, then through the LED, and then back to the battery. This causes the LED to light up. The brighter the LED, the higher the voltage of the battery.
You can use this improvised voltmeter to measure the voltage of any DC power source.