Power in physics is understood as the ratio of the work done in 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 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 apparatus. Thanks to the power measurement, it becomes clear how quickly the work is done.
Power Units
Power is measured in watts or joules per second. Motorists know the measurement of horsepower. By the way, before the advent of steam engines, this value was not measured at all.
Once, using a mechanism in a mine, engineer J. White set about improving it. To prove his improvement in the engine, he compared it to 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 power of one horse is 746 watts. Today, everyone is sure that this number is clearly overstated, but the power units have decided not to change.
By means of the aforementioned physical quantity, they learn about productivity, since when it increases, work increases over the same period of time. 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 is more understandable than other units of power.
How to understand the power in household electrical appliances
Power, of course, is indicated in household electrical mechanisms. Lamps use its specific values, for example sixty watts. Bulbs with a high power indicator can not be installed then, because 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 low power.
Energy consumption, of course, is directly proportional to the amount of power. Therefore, for manufacturers of bulbs there is always a field for improving the product. Currently, consumers increasingly prefer options other than incandescent lamps.
Sports power
Power units are not only known 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 its application.
You can even use computer programs with 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 with which power is measured. They are also used to determine force and torque. Devices are used in various industries. For example, they will show engine power. To do this, the motor is removed from the car 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 are also widely used. On the simulators there are often sensors that are connected to the 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 measurement of electric current power became a watt, and the value was included in the international measurement system 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 of various prefixes to the source word: "kilo", "mega", "gig", etc.:
- 1 kilowatt is equal to a thousand watts;
- 1 megawatt is equal to a 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 an off-system indicator introduced to account for consumed electrical energy. GOST 8.417-2002 with regulation is in force in Russia, where the unit of measurement of electric current power is directly indicated and applied.
This unit of measure is recommended to be used to account for consumed electrical energy. It is the most convenient form by which acceptable results are obtained. 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 a hyphen, and a short one through a period (W · h, kW · h).
How power is indicated in electrical appliances
It is customary to indicate the said indicator directly on the body of the electrical appliance. Possible notations are:
- watts and kilowatts;
- watt hour and kilowatt hour;
- volt-amperes and kilovolt-amperes.
The most universal designation is the use of units such as watts and kilowatts. If available on the device’s case, we can conclude that the indicated 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 basically the name of the current power, the unit of measurement in the device of which is primarily focused on the amount of heat received, and calculations are already taken into account following him.
Watt-hour and kilowatt-hour show power consumption for a given unit of time. Often these designations 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 volt-amperes and kilovolt-amperes. Such a measurement is provided to indicate AC power. They are used in technical calculations when electrical indicators are important.
This designation most closely meets 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 indicate the power of such devices as transformers, chokes, and other converters.
In this case, the manufacturer independently chooses which units of measurement to indicate to him, especially since in the case of low-power equipment (such as, for example, household electrical appliances), all three designations, as a rule, coincide.