Electricity

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Electric power and energy

Electric power and power rating

1) Voltage and current rating

Voltage and current ratings are the voltage and current received by a electric component or device operating under normal conditions.

When an electric device is exposed to its voltage rating then its current correspond to its current rating (and vice versa).

2) The electric power unit

The electrical power is a quantity used in electricity.
It is denoted with letter P and its unit is the watt (W)
We also use derived units:
- Kilowatt (kW):  1 ​​kW = 1000 W
- The megawatt (MW): 1 MW = 1,000,000 W
- The gigawatt (GW): 1 GW = 1 billion W
  etc.
An electric component or an electric device is also characterized by its power rating.

3) Relationship between electrical energy and electric power

Definition: Electrical power is the energy exchanged (received or given) during a second.
The power thus reflects the rate and extent with which energy is transferred or converted.

4) Meaning of power rating
The more power rating is high, the more efficience is high.
for instance, the more power rating is high:
- the brighter a lamp is.
- the more effective is suction of a vacuum cleaner.
- the louder are sounds produced by speakers.

Examples of power ratings: Plasma TV: 200W; iron 1 kW; washing machine 2 kW; an oven: 3 kW.

If the electrical power supplied to a device is less than its power rating then its efficiency is lower than expected.
If the electrical power supplied to a device exceeds its power rating then its efficiency is higher than expected but the deterioration comes faster.

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