A voltmeter measures the difference in electrical potential between two points in a circuit. Commercial voltmeters are highly accurate and available from electronics stores. You can also construct a simple analogue voltmeter at home from available materials. This type of voltmeter is a common school project, and you can use it to make relative measurements of small voltages. You can also calibrate your voltmeter to make absolute measurements by recording its response to known voltages.
- Skill level:
Things you need
- Spool of thread
- Fine copper wire
- Glue gun
- 1 flat piece of wood
- 2 small pieces of wood
- 2 flat pieces of plastic
- Sewing needle
- Small magnet
- Small battery
Make a magnetic coil by wrapping fine copper wire around a nonmagnetic core such as a spool of thread. Glue the coils of wire to hold them in place.
Place a flat piece of wood on a solid surface to serve as the base for the voltmeter.
Place two small pieces of wood vertically about 1 inch apart on the voltmeter's base. Glue the pieces in place to serve as bearing supports for the voltmeter.
Cut small grooves into two small pieces of plastic to accommodate a sewing needle. Glue the plastic pieces to the bearing supports for the voltmeter. These pieces of plastic will serve as bearings for the voltmeter.
Pierce a straw with a sewing needle near one of its ends. Glue the sides of the straw to the needle. The straw will serve as the needle for the voltmeter.
Position the magnetic coil from Step 1 between the bearing supports for the voltmeter. The free ends of the wire on the coil must be facing away from the bearing supports. Glue the coil to the base of the voltmeter.
Glue a small magnet to the end of the straw closest to the sewing needle. Place the sewing needle into the grooves of the bearings that you made in Step 4.
Place a small piece of metal at each end of the sewing needle, and glue them in place. These metal supports should keep the needle in the grooves but still allow it to rotate freely.
Connect the ends of the wire on the coil to a source of electricity, such as a small battery. The electrical current will allow the coil to generate an electromagnetic field. This will attract the magnet on the bottom of the straw, causing it to move. A higher voltage will generate a stronger electromagnetic field and cause a greater movement of the straw.
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