Power in physics is understood as the ratio of the work done in a certain time to the time interval for which it is performed. Mechanical work refers to the quantitative component of the impact of force on the body, due to which the latter moves in space.
Power can also be expressed as the rate of energy transfer. That is, it shows the performance of the automatic device. Power measurement makes it clear how fast the job is done.
Power units
Power is measured in watts or joules per second. Motorists are familiar with the measurement of horsepower. By the way, before the advent of steam engines, this value was not measured at all.
One day, using a mechanism in a mine, engineer J. White set out to improve it. To prove his improvement in the engine, he compared it with the performance of horses. People have been using them for centuries. Therefore, it was not difficult for anyone to imagine the work of a draft horse for a certain periodtime.
Watching them, White compared models of steam engines depending on the amount of horsepower. He experimentally calculated that the power of one horse is 746 watts. Today, everyone is sure that such a number is obviously overestimated, but they decided not to change the power units.
Through the named physical quantity, they learn about productivity, since when it increases, work increases over the same period of time. This 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 is more understandable to many than other units of power.
How power is understood in household electrical appliances
Power, of course, is also indicated in household electrical mechanisms. In lamps, its specific values \u200b\u200bare used, for example, sixty watts. Light bulbs with a high power rating cannot then be installed, otherwise they will quickly deteriorate. But if you buy not incandescent lamps, but LED or fluorescent ones, then they will be able to shine with greater brightness, while consuming little power.
Energy consumption, of course, is directly proportional to the amount of power. Therefore, there is always room for product improvement for light bulb manufacturers. Nowadays, consumers increasingly prefer options other than incandescent bulbs.
Sport power
Power units are known not only in connection with the use of mechanisms. The concept of power can be applied to both animals and people. For example, you can calculate this value when an athlete throws a ball or other equipment, getting it as a result of establishing the applied force, distance and time of application.
You can even use computer programs, with the help of which the indicator is calculated as a result of a certain number of exercises done and the introduction of parameters.
Measurements
Dynamometers are special devices that measure power. They are also used to determine force and torque. Devices are used in various industries. For example, they will show the power of the engine. To do this, the motor is removed from the car and connected to a dynamometer. But there are devices that are able to calculate what you are looking for even through the wheel.
Dynamometers are also widely used in sports and medicine. The simulators often have sensors that are connected to a computer. With the help of them all measurements are made.
Power in watts
James Watt invented the steam engine, and since 1889 the unit of electric power became the watt, and the value was included in the international system of measurements in 1960.
Watts can be measured not only electrical, but also thermal, mechanical or any otherpower. Multiple and submultiple units are also often formed. They are called with the addition of various prefixes to the original word: "kilo", "mega", "giga", etc.:
- 1 kilowatt equals one thousand watts;
- 1 megawatt equals one million watts and so on.
Kilowatt-hour
In the international SI system there is no such unit of measure as kilowatt-hour. This indicator is off-system, introduced to account for the consumed electrical energy. In Russia, GOST 8.417-2002 is in force with regulation, where the unit of measurement of electric current power is directly indicated and applied.
This unit of measurement is recommended to be used to account for the consumed electrical energy. It is the most convenient form with which acceptable results are obtained. Multiple units here can also be used if necessary. They look similar to watts:
- 1 kilowatt hour equals 1000 watt hour;
- 1 megawatt-hour equals 1000 kilowatt-hours and so on.
The full name is written, as you can already see, with a hyphen, and the short one - with a dot (Wh, kWh).
How power is indicated in electrical appliances
It is generally accepted to indicate the mentioned indicator directly on the body of the electrical appliance. Possible designations are:
- watt and kilowatt;
- watt-hour and kilowatt-hour;
- volt-ampere and kilovolt-ampere.
The most universal designation isusing units such as watts and kilowatts. If they are present on the body of the device, it can be concluded that the specified power develops on this equipment.
Often in watts and kilowatts they measure the mechanical power of electric generators and motors, the thermal power of electric heaters, etc. This is mainly the current power, the unit of measurement in the device of which is primarily focused on the amount of heat received, and calculations are taken into account after it.
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 watts and kilowatts - these are volt-ampere and kilovolt-ampere. This measurement is given for the indication of AC power. They are used in technical calculations when electrical indicators are important.
This designation is most consistent with the requirements of electrical engineering, where devices operating with alternating current have both active and reactive energy. Therefore, the electrical power is determined by the sum of these components. Often in volt-amperes they denote the power of such devices as transformers, chokes, and other converters.
At the same time, the manufacturer independently chooses which units of measurement to indicate to him, especially since in the case of low-power equipment (which are, for example, household electrical appliances), all three designations, asgenerally match.
