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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
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.

Science class




Electricity lessons
Electrical components
-Two-terminal electronic components
- Basic electrical components
- Diodes
- What's a resistor ?
- How to determine a resistor value ?
- Resistors effects in circuits
- How to use a resistor ?
- Characteristic curve of a resistor
How to build simple circuits and draw diagrams
- How to build a basic electrical circuit
- How to draw diagrams of electric circuits
The electric current
- Conductors and insulators
- Direction of electric current in a circuit
- The dangers of electricity
- Current intensity - units
how to measure current ?
The Voltage
- The voltage and its units
- How to measure a voltage ?
- Voltage in open and closed circuits
- Rated current and voltage for a lamp
Alternating voltage and current
- Alternating currents effects on led
- What are alternating current and voltage ?
- Periodic alternating voltage and its properties
- Oscilloscope
- Oscillogram
- Frequency
- Measuring RMS voltage with a voltmeter
Serie circuits
- What's a serie circuit ?
- Series circuit properties
- Short circuit in  series circuit
- Current law in series - circuits
- Voltage law in series circuits
Parallel circuits
- What's a parallel circuit ?
- Some parallel circuits properties
- Short circuits in parallel circuits
- Nodes and branches in parallel circuits
- Current laws in parallel circuits
- Voltage laws in parallel circuits
Laws of electricity
- Ohm's law
- Current laws in series circuits
- Voltage laws in series circuits
- Current laws in parallel circuits
- Voltage laws in parallel circuits
Generating electricity
- Voltage for coil wires
What is an alternator ?
- Alternating currents and voltages
- Generating electricity in power plants

Electric power and energy
- Electric power and power rating
- Electric power received by an electrical device
- Electric power consumption by an electrical device
- Relationship between - Electric power and energy


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