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What is a Milliwatt? Article Details
• Written By: G. Wiesen
• Edited By: Heather Bailey
• Last Modified Date: 09 October 2019
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A milliwatt (mW) is a measurement of power that can be used in a number of different fields for understanding various physical sciences. It is one thousandth of a watt (W), which is a measurement of power that represents the amount of power needed to exert one joule (J) of work per second (s). In electrical calculations done for experiments or research dealing with electromagnetism, it can be expressed in a number of different ways, though a watt often represents current multiplied by voltage. A milliwatt is a very small measurement of power, and is typically used in reference to small electrical devices.

In order to fully understand what a milliwatt represents, it is important to understand what a watt measures. The watt, named after inventor James Watt, is a measurement of power used to express the amount of work that must be done over a certain period of time. An object, for example, that is kept at a steady velocity of 1 meter per second (m/s) against a constant force of 1 newton (N) would have 1 watt of work being applied to it. This means that a milliwatt is one thousandth of the amount of power that would be needed to maintain 1 joule of energy for one second.

A joule is a unit of measurement for energy or work, which represents the amount of energy needed to apply a force of 1 newton over a distance of 1 meter. This is also known as a “newton meter,” and a newton is a unit of measurement used in describing an amount of force. When used in an electrical system, a watt represents the amount of power generated by 1 ampere (amp) of current moving through a system with potential energy of 1 volt. A milliwatt would, therefore, be one thousandth of the amount of power produced in a system of 1 volt that has a 1 amp charge flowing through it.

The milliwatt is a very small measurement with reference to the amount of power often used in major electrical systems. Most homes, for example, consume power that is rated in terms of kilowatts, or thousands of watts. When using the abbreviation for milliwatt, mW, it is important to properly capitalize only the “W,” since “MW” is used to represent megawatts. A megawatt represents 1 million watts, which is many orders of magnitude greater than the milliwatt. Milliwatts are typically used in electronics that are relatively small in scale, such as laser emitters that read compact discs (CDs).

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