The National MagLab is funded by the National Science Foundation and the State of Florida.

# Electricity Meter

The newest electric meters rely on different techniques to measure usage. But power to many homes and businesses is still monitored by traditional meters like the one explained in this tutorial. It also shows how usage of various appliances impacts power consumption.

The standard electric meter seen here works by electromechanical induction. Three magnetic fields are in play.

## Instructions

1. Take a close look at the mechanics of the meter.
2. Note the oval shaped permanent magnet at the lower left. See how its poles are positioned around the metal disc that rotates in relation to power usage.
3. Unseen inside the meter are two induction coils. One is connected to produce magnetic flux in proportion to the voltage moving through the meter. The other produces magnetic flux in proportion to the current moving through the meter.
4. The magnetic flux from the two coils produces eddy currents, creating a force on the metal disc. The permanent magnet exerts an opposing force, so the disc rotates at a speed proportional to energy usage in kilowatt hours.
5. Experiment by selecting which household appliances you want to turn on, and see how it impacts electricity consumption.
6. Use the dropdown menus to change the hours per day that the appliances are used and the unit price of electricity to calculate monthly utility costs.