A watt is a physical quantity that everyone has to deal with every day without even knowing it. What is it measured when it arose and by what formula can it be found? Let's find the answers to all these questions.
What is a watt?
First of all, you should find out the definition of this term. So, a watt is a unit of power used in the SI International System.
It can be of three types:
- Mechanical
- Electric.
- Thermal.
It is generally accepted that 1 watt is such a power at which work (A) in 1 joule is performed in 1 second (t).
Appearance story
For the first time, they began to use watts as a value for measuring power in the UK in 1882. Before that, horsepower was in use, and in some countries their understanding was different.
The inventor of this unit of measure (watts) was the "father" of the industrial revolution - James Watt (there is a variant of writing Watt). In honor of him, by the way, she was named. For this reason, just like the joule (named after the name of the British scientist James Prescott Joule), the watt is always abbreviated with a capital letter - W (in English W).
Since 1960, watt has been the power unit used worldwide. After all, it was then that he was recognized by the SI system.
Power formula
Having dealt with the definition and history of the appearance of a watt, it is worth knowing its formula. It looks like this: N = A / t. And it stands for work divided into time.
Sometimes, in order to find out the number of watts, the power formula is used slightly different: N = F x V. In this example, the desired value is calculated not using work and time, but using force and speed data.
In fact, the second formula is a kind of adaptation of the classic. It’s just taken into account that the work is equal to the derivative of the force by the distance (A = F x S), and the speed is the quotient of dividing the distance by time (V = S / t). If you put all this data: you get the following example: N = F x S / t = F x V.
Watts, volts and amperes
In addition to the formula considered in the previous paragraph for the search for the studied physical quantity, there is another. It demonstrates the relationship of power (watts), voltage (volts) and current strength (amperes).
However, before you become familiar with it, it is worth learning a little more about these units.
Volt (V, in English V) is a unit of measurement of electrical voltage. In the formulas is denoted by the Latin letter U.
Ampere (A, in English also A) - a value characterizing the strength of an electric current, indicated by the letter I.
The formula for the relationship between power, voltage and current
Briefly considering the features of all these quantities, we obtain this formula.
It looks like this: P = U x І. In it, P is power (watts), U is voltage (volts), I is current (amperes).
If necessary, this formula can be simulated if the power is already known, but it is necessary to find the current strength (I = P / U) or voltage (U = P / I).
With the modern development of technology, in order to find out how many watts are contained in a certain number of amperes, you can simply find a specialized power calculation program on the Internet and enter the available data into it. It is not difficult to do this, in the line of any search engine you need to look for the phrase "calculator converting watts to amperes", and the system will give out the addresses of the necessary sites.
Fractional units of W
In addition to practical application, the units in question are often used to perform numerous theoretical calculations. However, if the power is extremely small, writing watts using decimal fractions with multiple zeros is pretty impractical. To facilitate this task, scientists introduced fractional units of watts. Usually they are written in the form of degrees with a minus.
To date, there are a dozen of them allocated, but in practice, many of them are not used.
For example, the first two fractional units of a watt: dW (decivatt, equal to 10 -1 W) and sW (centivatt, equal to 10 -2 W) are not recommended for use. But milliwatts (mW, equal to 10 -3 ), microwatts (μW is equal to 10 -6 ) and nanowatts (nW is equal to 10 -9 W) - one of the most used. And not only in the calculations, but also in the manufacture of various measuring instruments.
For example, in medical devices such as an electrocardiograph and an electroencephalograph, units of measure are microwatts (µW).
In addition to the above, there are five more fractional units: picovatt (10 -12 ), femtowatt (10 -15 ), attatt (10 -18 ), zeptowatt (10 -21 ) and ioctowatt (10 -24 ). However, all of them are used in rare cases, and then only in theoretical calculations.
Multiples of W
The unit in question is relatively small. For example, to wash one kilogram of laundry in one hour in an A ++ class automatic washing machine, you need 150 watts of electricity. However, if we take into account that on average about 3.5 kilograms of things are simultaneously erased, it means that 525 watts are spent. And this is just one wash, and how many of them occur in a month or a year? A lot, as well as the amount of watts consumed. To facilitate their recording, ten multiple units are recorded on the basis of W, written in the form of degrees.
As in the case of fractional values, the first two of them (decavatt - 10 1 and hectowatt - 10 2 ) are not accepted to be used, so they only exist “de jure”.
It is worth noting that when writing abbreviations of multiple units, often the first letters are capital letters. This is done so as not to confuse megawatts (MW - 10 6 ) with microwatts (mW) and other similar values.
The most used is the well-known to all - kilowatts (kW). It is equal to a thousand watts (10 3 ). The second most popular is the aforementioned megawatt. This unit is most often used in the field of electricity. Less commonly, such quantities are used in it as gigawatts (GW - 10 9 ) and terawatts (TW - 10 12 ). For example, in one year, on average, humanity consumes about 1.9 TW of electricity.
The remaining four values - petawatts (PW - 10 15 ), exawatts (EW - 10 18 ), zettawatts (ZW - 10 21 ) and iottawatts (IW 10 24 ) - are very rarely used, mainly in theoretical calculations. For example, according to one of them, it is assumed that the total power of the energy radiated by the Sun is 382.8 IW.
Despite the many multiple and fractional units of a watt, it is not difficult to carry out mathematical operations with them. The easiest way to translate everything into watts and then perform actions with degrees.
Another simple way to find out watts (the amount when using large or small quantities associated with them) is to find an online calculator on the Internet. By the way, with its help it is possible to convert W even to horsepower.
Watts and Watts
Having dealt with the fact that the unit of measurement of watts (as well as finding out its multiple and fractional values and formulas for finding), it is worth taking the time to consider such a close concept as a watt-hour (Wh). Although the names for W and Wh are very similar, they mean slightly different concepts.
The second unit is used to measure the energy produced in a given time period (one hour).
To make the difference more understandable, it is worth considering the work of an ordinary electric kettle, with a power of 2200 watts. To prepare compotes for the winter, the hostess almost continuously heated water with it for one hour. During this time, the device used 2200 Wh. If a woman took a weaker kettle of 1100 watts, he would boil the same amount of liquid in two hours and still use the same 2200 Wh.
All electricity supplied to consumers is not measured in watts, namely, in watt hours (more often in kilowatt hours, also a ratio of one in a thousand). To confirm this, you can simply go to any home counter. Regardless of the country and manufacturer, near the numbers (showing the amount of electricity used) will be marked "kilowatt hours" (kWh). It can also be in English: kilowatt-hour (kW⋅h).
Moreover, the power of any power plant synthesizing it is measured in ordinary watts (kilowatts and megawatts).