Small batteries, such as AAs, are rated in milliamp-hours.
Amps and milliamps measure current, or the number of electrons that pass through a point over a period of time. Electricians and electrical engineers use amps when discussing generators, cables and outlets. They use milliamps, which represent one-thousandth of an amp, to describe devices that use or generate a small amount of current, such as low-wattage light bulbs and household batteries. Ampere-hours and milliamp-hours are similar units, which measure how long a given amount of current can be transferred. Amps and ampere-hours can be converted to milliamp units by multiplying by 1,000.
Amps
Amp is short for ampere, the metric base unit of current. It was named after Andr -Marie Ampere, a French physicist and mathematician who discovered that a magnetic field could generate an electric current in a nearby conductor. As of June 2011, the official definition of the ampere is a current that creates 2 x 10^-7 newtons of force per meter of length in two parallel conductors one meter apart. The Consultive Committee for Units (CCU), however, has proposed a new definition that it plans to propose to the General Committee on Weights and Measures in October 2011. According to this definition, an ampere would be the current equal to the flow of 1/1.60217X x 10^-19 electrons per second.
Milliamps
A milliamp (mA) is one-thousandth of an amp. This is called a metric derived unit because it is created by combining a metric prefix, which stands for a power of 10, with a base unit. In this case, the prefix "milli-" (10^-3), or one-thousandth, combines with the amp unit to symbolize a quantity that is equal to 1/10^3 amps.
Conversion Factor
To convert amps to milliamps, you must multiply the number of amps by 1,000. A simple way to perform this conversion is to move the decimal point three places to the right. For instance, 9.289 amps equals 9,289 milliamps. To convert a whole number, add three zeroes. For example, 25 amps equals 25,000 milliamps.
Ampere-hours to Milliamp-hours
The amount of charge transferred by one amp in one hour is called an ampere-hour (Ah). Battery capacity is measured using this unit. It is cumbersome, however, to describe the output of a small battery, such as a 9-volt or an AA, in terms of fractions of an ampere-hour. Instead, the units are converted to milliamp-hours (mAh). To perform this conversion, multiply the number of ampere-hours by 1,000. For instance, a battery with a rating of 0.75 ampere-hours has an equivalent rating of 750 milliamp-hours.
Tags: amount current, amps equals, amps equals milliamps, base unit, definition ampere
