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# Electric power

Electric power transmission uses cables and electricity pylons like this near Bartholomä in Germany

Electric power is defined as the power dissipated by an electric circuit. Electric power is a measurement of the rate at which energy is used over a period of time. The SI unit for power is the watt, the unit for energy is the joule, and the unit for time is the second.

For a direct current circuit, electric power equals the electric current multiplied by the voltage.

When electric current flows through a circuit, it is slowed down by the resistance in the circuit. Devices can convert this current to useful forms of work, such as heat radiation, light emission, mechanical motion, or acoustic vibrations.

## References

      . http://books.mcgraw-hill.com/getbook.php?isbn=0071377352. Retrieved 2007-04-09.

      . http://books.mcgraw-hill.com/getbook.php?isbn=0070220050. Retrieved 2007-04-09.


da:Effekt (fysik)#Effekt i elektriske kredsløb