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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 = V
_{RMS}× I_{RMS}where V_{RMS}and I_{RMS}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.

- 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.

An electrical device has a **rated voltage** and **rated current**. These are the values of voltage and current to ensure normal operation of the device. The **rated power** is the product of the two…