### Education, The science

# Units of power. Power: unit of measurement

Power in physics is understood as the ratio of the work done for a certain time to the period of time for which it is performed. By mechanical work is meant the quantitative component of the effect of force on the body, because of what the latter moves in space.

One can express the power and the speed of energy transfer. That is, it shows the operability of the automatic device. By measuring the power, it becomes clear how quickly the work is done.

## Units of power

The power is measured in watts or joules per second. Motorists know the measurement of power in horsepower. By the way, before the advent of steam engines, this value was not measured at all.

Once, using the mechanism in the mine, engineer J. White took up his improvement. To prove his improvement of the engine, he compared it with the performance of horses. People have used them for centuries. Therefore, it was not difficult for anyone to imagine the work of a draft horse for a certain period of time.

Watching them, White compared the models of steam engines depending on the amount of horsepower. He experimentally calculated that the horsepower of one horse is 746 watts. Today, everyone is sure that such a number is clearly overstated, but the units of measurement of power have decided not to change.

By means of the named physical quantity learn about productivity, as at its increase the work for the same time interval increases. Such a standardized unit of measurement has become very common. It began to be used in a variety of mechanisms. Therefore, although watts have been used for a long time, horsepower for many people is more understandable than other power units.

## How to understand the power in household electrical appliances

Power, of course, indicates in domestic electrical mechanisms. Luminaires use certain values, for example sixty watts. Lamps with a large power rating can not be set, because otherwise they will quickly deteriorate. But if you buy not incandescent lamps, but LED or luminescent, they can shine with greater brightness, while consuming a small power.

Energy consumption, of course, is directly proportional to the amount of power. Therefore, for manufacturers of light bulbs there is always a field for product improvement. Currently, consumers increasingly prefer other options, except for incandescent lamps.

## Sports Power

Units of power are known not only in connection with the use of mechanisms. The concept of power can be attributed to animals and to humans. For example, you can calculate this value when an athlete throws a ball or other inventory, getting it as a result of setting the applied force, the distance and the time of its application.

You can use even computer programs, through which the indicator is calculated as a result of a certain number of exercises and the introduction of parameters.

## Measuring instruments

Dynamometers are special devices that measure power. They are also used to determine the force and torque. Appliances are used in a wide range of industries. For example, they will show the power of the engine. For this, the motor is extracted from the vehicle and connected to a dynamometer. But there are devices that are able to calculate the desired even through the wheel.

In sports and medicine, dynamometers also find widespread use. The simulators often have sensors that are connected to the computer. With their help, all measurements are made.

## Power in Watts

James Watt invented a steam engine, and since 1889 the unit for measuring the power of electric current has become a watt, and in the international measurement system the value was included in 1960.

In watts, not only electrical, but also thermal, mechanical or any other power can be measured. Multiple and fractional units are also often formed. They are called with the addition to the source word of various prefixes: "kilo", "mega", "giga" and others:

- 1 kilowatt is equal to a thousand watts;
- 1 megawatt is equal to one million watts and so on.

## Kilowatt hour

In the international SI system, there is no such unit of measurement as kilowatt-hour. This indicator is extra-systemic, introduced to account for the expended electrical energy. In Russia there is GOST 8.417-2002 with regulation, where the unit for measuring the power of electric current is directly designated and applied.

This unit of measurement is recommended to be used to account for the expended electrical energy. It is the most convenient form by which to obtain acceptable results. Multiple units here can also be used if necessary. They look similar to watts:

- 1 kilowatt-hour is equal to 1000 watts-hour;
- 1 megawatt-hour is equal to 1000 kilowatt-hours and so on.

The full name is written, as already seen, through the hyphen, and a short one is written through the point (W · h, kW · h).

## How is power in electrical appliances

It is generally accepted to indicate this indicator directly on the body of an electrical appliance. Possible designations are:

- Watt and kilowatt;
- Watt-hour and kilowatt-hour;
- Volt-ampere and kilovolt-ampere.

The most universal designation is the use of units such as watts and kilowatts. If they are available on the body of the device, it can be concluded that this equipment develops the indicated power.

Often in watts and kilowatts, the mechanical power of electric generators and motors, the thermal power of electric heating devices, etc. are measured. This is basically the current power, the unit of measurement in the instrument of which is primarily oriented toward the amount of heat received, and the calculations are already taken into account Following him.

Watt-hour and kilowatt-hour show the power consumption for a given unit of time. Often these symbols can be seen on household electrical appliances.

In the international SI system, there are units of electrical power that are equivalent to a watt and a kilowatt - these are the volt-ampere and kilovolt-ampere. This measurement is given to indicate the AC power. They are used in technical calculations when electrical indicators are important.

This designation most closely corresponds to the requirements of electrical engineering, where devices working with alternating current have both active and reactive energy. Therefore, the electrical power is determined by the sum of these components. Often in volt-ampere designate the power of such devices as transformers, chokes, and other converters.

At the same time, the manufacturer chooses which units of measurement to specify, especially in the case of low-power equipment (which are, for example, household electrical appliances), all three designations, as a rule, coincide.

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