# Electric Power and EnergyHTML5

## Summary

The electric power P "consumed" by an electrical device is the product between the voltage V at the terminals (in Volts) and current I passing through it (in amps):
P = V × I

The unit of power is the Watt (W).

• For direct current, P = V × I
• For alternating current used with resistance type components (lamps, heaters), P = VRMS× IRMS where  VRMS and IRMS are the RMS values of voltage and current.

The electrical energie consummed by an electrical appliance is the product of electrical power (P) and the duration of time used (t)

E = P × t

The unit of energy is the Joule (J). Another frequently used unit is the Watt-hour (Wh). Look at your home electricity bill.

1 WH = 3600 J

In the power animation, click and slide the voltage icon to adjust the voltage supplied to the circuit.

In the DC and AC Energy animations, click and slide the meter(s) to see changes in energy consumption.

## Learning goals

• To learn how to measure power of an electrical device.
• To learn how to measure the electrical energy consumed by an electrical device for a period of time.
• To understand the function of an electric meter and how electrical energy consumed is indicated on the electric bill.