A voltmeter is a device that measures the difference in electrical potential between two points of an electrical circuit. Voltmeters come in a variety of styles. They may be permanently mounted in an electrical panel to monitor the voltage in a particular circuit or they may be more portable so they can measure the voltage of different circuits. Commercial voltmeters generally use complex electronic circuits, but you may also build a simple voltmeter from commonly available parts.
Things You'll Need
- 1 piece of cardboard, 6 inches x 12 inches
- 2 flat pieces of plastic
- 2 small pieces of metal
- 4 small pieces of wood
- Glue gun
- Sewing needle
Find or make a coil. The coil should be made of very fine copper wire wrapped around a nonmagnetic core. You can commonly find a usable coil from an old electrical device and remove all the magnetic parts from it. You could also wind a coil yourself with enough time and patience.
Make the frame for the voltmeter. Use one piece of wood as the base of the voltmeter and glue two other pieces of wood to this base which will support the bearings for the voltmeter. These bearing supports should be of equal height and about a half inch apart. Cut small narrow grooves in the pieces of plastic to serve as the bearings for the voltmeter and glue them to the bearing supports.
Glue a fourth piece of wood to the side of the bearing supports. Glue the coil on top of this piece so that the coil terminals are facing away from the bearing supports.
Attach a very small magnet to the bottom of the straw and push the sewing needle all the way through the straw near the end that has the magnet. Place the sewing needle in the bearing grooves that you made in Step 2 so that the coil will repel the magnet when a current goes through it.
Glue the two pieces of metal at the ends of the needle to stabilize it and keep in the grooves. Now tilt the base of the platform so that the magnet comes to rest very close to the coil. When a current is applied to the coil, it will produce an electromagnetic current in the coil that will repel the magnet and make the top end of the straw swing to the side. When the current flow stops, gravity will pull the straw back to its zero point.