Wattage is a measurement of energy over a period of time and is the term of measurement for electrical energy. Devices and all other items that use electricity have an ideal input and output wattage, which indicates how much electrical energy they require to run and how much they emit. Wattage is calculated by multiplying potential electrical energy by electrical current.

Potential electrical energy is voltage; the force exerted on charge to make it move. Electrical current is measured in amperes; one unit of electrical charge (coulombs) per second. Multiplied together, voltage and amperes equal wattage:

If W = V x A

Each electrical device that has a rechargeable battery inside must receive a higher voltage than the current voltage within the depleted battery. When the device is plugged into the wall, the ensuing voltage provides new electrical charge to the battery within it.

Each item (such as a lamp or vacuum cleaner or anything that needs electricity) has an ideal input wattage, which indicates how much electrical energy the item needs to be powered. If that wattage is exceeded, the item could be damaged because the current overpowers the circuits-it can’t handle that level of electrical power. This can damage the item, or it can cause electrical fires and could destroy property. Items also have an ideal electrical output in watts-how much energy the item emits when sufficiently powered. This includes computers, phones, and other electronic devices. Resistors and amplifiers within a circuit regulate the power that the circuit outputs, controlling the voltage and amps so that the circuit maintains the right flow of current.

Wattage is also how electric companies measure and track electricity use.


Jenna Phipps
Jenna Phipps
Jenna Phipps is a writer for Webopedia.com, Enterprise Storage Forum, and CIO Insight. She covers data storage systems and data management, information technology security, and enterprise software solutions.

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