In 1882, the British Science Association decided to start using a new unit of measurement called the watt. What is it used for today, what is it equal to and by what formula can it be calculated? Let's find the answers to all these questions.
Watt is a unit of measure for what?
Since that fateful year when the British introduced the tradition of using the watt, they gradually began to switch to it all over the world, instead of outdated and impractical horsepower. With the advent of the SI system, it was introduced into it and began to be used everywhere.
So, what physical quantity has a unit of measurement "watt"? Remember the lessons of physics: the correct answer to this question is power.
Watt got its name in honor of his "father" - the Scotsman James Watt. In abbreviation, this unit is always written with a capital letter - W (W - according to international standards of the SI system), and in full - with a small "watt" (watt).
Being not a basic, but a derived unit (according to the SI standard), the unit in question depends on the meter, kilogram and second. In practice, this means that one watt is the power at which one joule of work is performed in one second of time. That is, the following dependence is obtained: 1W = 1J / 1s = 1H x m / s = kg x m 2 / s 3 = kg x m 2 x s -3.
In addition to those listed above, watt is associated with non-system units. For example, with a calorie. So 1 W = 859.845227858985 cal / hour. This ratio is important when it comes to calculating the amount of heat generated by an electric heater.
Formula
So, watt is a unit of measure for power. Let's look at what formula it can be calculated.
As mentioned above, the power depends on the work and the time. The following formula is obtained: P = A / t (power is equal to the quotient of the division of work by time).
Knowing that the formula of work is equal to: A = F x S (where F is force, S is distance), you can use this data.
As a result, we get the formula: P = F x S / t. And since S / t is speed (V), then the power can be calculated like this: P = F x V
Interdependence of ampere, watt, volt
The unit of measurement that we are considering is directly related to such quantities as voltage (measured in volts) and current (measured in amperes).
1 watt is constant power electric current at a voltage of 1 V and a force of 1 A.
In the form of a formula, it looks like this: P = I x U.
Watts, kilowatts, megawatts and microwatts
Having learned that a watt is a unit of measurement of power, what quantities it depends on and what formulas it is easier to calculate, it is worth paying attention to concepts such as kilowatts, megawatts and microwatts.
Since W is a very modest value (such is the transmitter power of any mobile phone), in the electric power industry it is more common to use the kilowatt (kW).
Judging by the standard "kilo" prefix for the SI system, we can conclude that 1 kW = 1000 W = 10 3 W. Therefore, to convert watts to kilowatts, you just need to divide their number by a thousand, or vice versa, if kilowatts are converted to watts.
For example, a typical passenger car has a capacity of 60,000 watts. To translate this into kilowatts, you have to divide 60,000 by 1,000 and the result is 60 kW.
Kilowatts are the commonly accepted unit for measuring the power of electricity. In this case, a large multiple of the watt is sometimes used. We are talking about a megawatt - MW. It is equal to 1,000,000 watts (10 6) or 1,000 kilowatts (10 3).
For example, the British Eurostar electric train has a capacity of 12 megawatts. That is, it is 12,000,000 watts. Not surprisingly, it is the fastest in the UK.
Despite its modest size, sometimes this unit turns out to be too large to measure the power of certain objects, therefore, along with multiples in the C system, sub-multiples of a watt are also allocated. The most commonly used of these is microwatt (μW - spelled with lowercase letter not to be confused with a megawatt). It is equal to one millionth of a watt (10 -6). Usually this unit is used when calculating the power of work of electrocardiographs.
In addition to the three above, there are about two dozen other multiples and sub-multiples of watt units. However, they are most often used in theoretical calculations, and not in practice.
Watt hour
Considering the features of the watt (power unit), let's pay attention to the watt-hour (Wh). This term is used to measure a quantity such as energy (sometimes work is measured in watt-hours).
1 watt-hour is equal to the amount of work done in one hour at a power of 1 watt.
Since the unit in question is quite small, the kilowatt-hour (kWh) is often used to measure electricity. It is equal to 1000 watt-hours or 3600 W s.
Please note that the power generated at power plants is measured in kilowatts (sometimes megawatts), but for consumers, its amount is calculated in kilowatt-hours (less often in megawatt-hours, when it comes to megacities or huge enterprises).
Note that besides the kilowatt-hour and megawatt-hour, the watt-hour has exactly the same multiples and sub-multiples as the regular watt.
What device is called a wattmeter
Having compared the definition of a watt (a unit of measurement of power) and a watt-hour (a unit of energy or work), pay attention to such a device as a wattmeter (wattmeter). It is used to measure the active power of an electric current.
A classic device of this kind consists of four contacts, two of which are used to connect the wattmeter to an electrical circuit in series with that part of it, the power consumption of which is being measured at the moment. The other two pins are connected in parallel to it.
Wattmeters are usually created on the basis of electrodynamic mechanisms.
Power- a physical quantity equal to the ratio of the work done to a certain period of time.
There is a concept of average power over a certain period of time. Δt... Average power is calculated using this formula: N = ΔA / Δt, instantaneous power according to the following formula: N = dA / dt... These formulas have a rather generalized form, since the concept of power is present in several branches of physics - mechanics and electrophysics. Although the basic principles for calculating power remain approximately the same as in the general formula.
Power is measured in watts. A watt is a unit of measure for power equal to a joule divided by a second. In addition to the watt, there are other units for measuring power: horsepower, erg per second, mass-force meter per second.
- One metric horsepower equal to 735 watts, English - 745 watts.
- Erg- a very small unit of measurement, one erg is equal to ten to the minus seventh power of a watt.
- One mass-force-meter per second is equal to 9.81 watts.
Measuring instruments
Basically, measuring instruments for measuring power are used in electrophysics, since in mechanics, knowing a certain set of parameters (speed and force), you can independently calculate the power. But in the same way in electrophysics, you can calculate the power by parameters, but in fact, in Everyday life we simply do not use measuring instruments to record mechanical power. Since most often these parameters for certain mechanisms are already designated. With regard to electronics, the main device is a wattmeter used in everyday life in the device of an ordinary electric meter.
Wattmeters can be divided into several types by frequency:
- Low frequency
- RF
- Optical
Wattmeters can be both analog and digital. Low-frequency (LF) consists of two inductors, they are both digital and analog, they are used in industry and everyday life as part of ordinary electricity meters. RF wattmeters are divided into two groups: absorbed power and transmitted power. The difference lies in the way the wattmeter is connected to the network, the passing ones are connected in parallel to the network, absorbed at the end of the network as an additional load. Optical wattmeters are used to determine the power of light fluxes and laser beams. They are mainly used in some industries and in laboratories.
Power in mechanics
Power in mechanics is directly related to the strength and work that this power does. Work is a quantity that characterizes the force applied to a body, under the action of which the body travels a certain distance. Power is calculated by the scalar product of the velocity vector by the force vector: P = F * v = F * v * cos a
(force multiplied by the velocity vector and the angle between the force and velocity vector (cosine alpha)).
You can also calculate the power of the rotational movement of the body. P = M * w= π * M * n / 30... Power is equal to (M) moment of force multiplied by (w) angular velocity or pi (n) multiplied by moment of force (M) and (n) speed divided by 30.
Power in electrophysics
In electrophysics, power characterizes the rate at which electricity is transmitted or converted. There are such types of power:
- Instantaneous electrical power. Since power is the work done in a certain time, and the charge moves along a certain section of the conductor, we have the formula: P (a-b) = A / Δt... A-B characterizes the area through which the charge passes. A is the work of the charge or charges, Δt is the time the charge or charges pass through the section (A-B). The same formula is used to calculate other power values for different situations when you need to measure the instantaneous power on a section of the conductor.
- You can also calculate the power of a constant flow: P = I * U = I ^ 2 * R = U ^ 2 / R.
- Power alternating current cannot be calculated using the DC formula. In alternating current, three types of power are distinguished:
- Active power (P), which is P = U * I * cos f ... Where U and I are the effective parameters of the current, and f (phi) is the shift angle between the phases. This formula is given as an example for a single phase sinusoidal current.
- Reactive power (Q) characterizes the loads created in devices by oscillations of the electric single-phase sinusoidal alternating current. Q = U * I * sin f ... The unit of measurement is reactive volt-ampere (var).
- Apparent power (S) is equal to the square root of the active and reactive power. Measured in volt-amperes.
- Inactive power is a characteristic of the passive power present in AC circuits with sinusoidal currents. Equal square root the sum of the squares of reactive power and harmonic power. In the absence of the power of higher harmonics, it is equal to the reactive power modulus.
- Power alternating current cannot be calculated using the DC formula. In alternating current, three types of power are distinguished:
Car manufacturers from different countries measure the power of their vehicles in various units. What for? You will find out the answer below.
When reading an article about cars, be sure that you will always come across this data. With which? With car power data. Car engine power is one of the most important indicators that is relevant at any time, in any situation. From both practical and theoretical points of view.
Always up to date. According to statistics, one of the most interesting pieces of information about new products for readers lies precisely in the power of car engines. Thus, on a subconscious level, people compare models, their advantages and weak sides relative to each other only one power parameter motor.
Power as a matter of fact is a measure of how quickly and how far an engine can, through physical work, propel a car forward using torque. In mechanical engineering, this phenomenon is summarized by the concept of the amount of "work" that the power unit of a car must perform in order to propel the car forward. As a measure of measurement, such work has received many different units over time. We will take a closer look at some of them today.
Kilowatts (kW)
From a technical point of view, this form of measurement is the most universal method power calculations. It is used by engineers all over the world.
Watt is a SI unit of measurement (International System of Units), which means how much power is required to perform work in 1J per unit of time.
Mostly used by professionals, as more "correct" in terms of basic science power indicator. As a unit of measurement in the automotive industry is used mainly in the Southern Hemisphere, so it has historically developed.
The method of measuring power in kilowatts on cars mainly occurs by finding the amount of torque transmitted from the wheels on a dynamometer, then this equation is used for calculations:
Kilowatts have become a modern measure for fixing the power output of cars and perhaps in the future they will become a generally accepted global measure. At least if you look at any of the official figures offered by automakers, you will definitely see the units of kW of power of internal combustion engines on par with horsepower.
Moreover, as the hype around electric cars begins, the introduction of this form of measurement will become even more justified, because the amount of work produced by an electric motor is measured using kWh (kilowatt-hours), which determine how long an electric motor can produce a certain amount of energy, for example, for driving a car.
Horsepower (hp)
Introduced into everyday life by the "maestro" and part-time the creator of productive steam engines - Mr. James Watt - a unit of power based on horsepower is somehow alive to this day, carrying the calculations of a brilliant engineer through the centuries. It is the main unit for measuring the power of cars in many countries, including Russia, it is used not only as a measurement of the power of an internal combustion engine in official documents for car models, but also for calculating taxation in the automotive sector, for example, calculating transport tax.
So what is horsepower (hp)? How did it come about and how is it calculated? How was her appearance related to horses?
Scotland, inventor James Watt brought to mind his first steam device that could help hundreds of industrialists and artisans in their everyday work. And it seems that the engine was good for everyone, but how to explain this to the townsfolk? The answer suggested itself, it was necessary to compare the work of the most widespread at that time "power device" (horse) with the work of a new machine. No sooner said than done, Watt sat down to count.
COUNTING AND COMPARISON OF UNITS OF MEASUREMENT
In most European countries, horse power is defined as 75 kgf free fall 9.8 m / s.
In the International Metric System, SI is officially measured in watts. 1 h.p. (metric horsepower) is 735 W or 0.73 kW.
In turn, 1 kW is equal to 1.35 hp.
Moreover, in the measurement system in the United Kingdom, as well as in the United States, horsepower (hp) equates to 745 watts, which is why there is a slight discrepancy with European "horses". Thus, 1 hp. in the USA is equal to 1.0138 hp. from Europe.
For example, the power of a 3.8 liter engineNissanGT-R is 570 h.p., in kilowatts it will be equal to 419
, in hp 577
units.
See also:
How James Watt introduced steam engines and horsepower
Now no one knows for sure how strong the horses that participated in Watt's experiments were, whether they were in their prime or they were old nags. However, several legends have survived.
According to one of which, a certain brewer, the first buyer of Watt's steam unit, probably in order to bring down the price of the inventor's car, decided to hold a competition. A horse in a brewery powered a water pump, and a brewer wanted to buy a steam engine instead.
In order to win for sure, an industrialist who was not clean on hand chose the strongest horse for competition and, by manipulating the whip and other tools to increase labor productivity, squeezed out of the poor beast maximum efficiency... In response to the challenge, James Watt, using his car, exceeded the work performed by the horse by 1.5 times according to some sources, which was taken as a model. metal device working on steam.
The second legend, on the contrary, tells us that Watt himself slightly "twisted" the calculations in his favor. It took him to convince the recalcitrant coal mine owners to switch from draft horses to steam engines... In the 18th century, the coal from their mines was lifted by horses with a rope through a system of blocks. After calculating the performance of an average horse, Watt applied a factor of 1.5 multiplying that number, making his machine easily outperforming any horse doing the same job.
Since horsepower has spread significantly throughout The globe due to the simplicity of calculations and clarity for users, there were different kinds(definitions) horsepower: metric horsepower, mechanical horsepower, boiler hp, electric hp and water horsepower.
Perhaps in some articles and news, both foreign and domestic, you have repeatedly come across incomprehensible abbreviations, for example: nhp,rhp, bhp, shp, ihp, whp... What do they mean?
Nhp orrhp,Nominalhorsepower,ratedhorsepower- net power, used to estimate the power of steam engines.
Bhp,Brakehorsepower- effective power in hp, the power “removed” from the crankshaft of the internal combustion engine, does not take into account the power loss from the gearbox and transmission of the vehicle.
Shp,Shafthorsepower- the power of the engine on the shaft, this is the power supplied to the propeller shaft, to the turbine shaft or to the output shaft of an automobile gearbox. Gross
Ihp,Indicatedhorsepower- Indicated power in hp, this is the theoretical power of a piston engine, determined by the sum of power from the crankshaft, effective power, and energy consumed for friction.
The concept of power (M) is associated with the productivity of a particular mechanism, machine or engine. M can be defined as the amount of work done per unit of time. That is, M is equal to the ratio of work to the time spent on its implementation. In the generally accepted international system of units (SI), the single unit of measurement for M is the watt. Along with this so far alternative indicator M is still horsepower (hp). In many countries of the world it is customary to measure M of internal combustion engines in hp, and M of electric motors in watts.
Varieties of EIM
With the development of scientific and technological progress, a large number of different power measurement units (UIM) appeared. Among them today, such as W, kgcm / s, erg / s and hp are in demand. In order not to introduce confusion when switching from one measurement system to another, the following EIM table was compiled, in which the real power is measured.
Tables of relationships between EIM
| EIM | W | kgcm / s | erg / s | h.p. |
|---|---|---|---|---|
| 1 Watt | 1 | 0,102 | 10^7 | 1.36 x 10 ^ -3 |
| 1 kilowatt | 10^3 | 102 | 10^10 | 1,36 |
| 1 megawatt | 10^6 | 102 x 10 ^ 3 | 10^13 | 1.36 x 10 ^ 3 |
| 1 kgcm per second | 9,81 | 1 | 9.81 x 10 ^ 7 | 1.36 x 10 ^ -2 |
| 1 erg per second | 10^-7 | 1.02 x 10 ^ -8 | 1 | 1.36 x 10 ^ -10 |
| 1 h.p. | 735,5 | 75 | 7.355 x 10 ^ 9 | 1 |
Measuring M in mechanics
All bodies in real world are set in motion by the force applied to them. The impact on the body of one or more vectors is called mechanical work (P). For example, the traction force of a car drives it. This is how mechanical R. is accomplished.
From a scientific point of view, P is the physical quantity "A", determined by the product of the magnitude of the force "F", the distance of movement of the body "S" and the cosine of the angle between the vectors of these two quantities.
The formula for work looks like this:
A = F x S x cos (F, S).
M "N" in this case will be determined by the ratio of the amount of work to the period of time "t" during which the forces acted on the body. Therefore, the formula defining M will be as follows:
Mechanical M motor
The physical quantity M in mechanics characterizes the capabilities of various engines. In M cars, the engine is determined by the volume of the liquid fuel combustion chambers. M of a motor is work (the amount of energy generated) per unit of time. The engine, during its operation, converts one type of energy into another potential. In this case, the motor translates thermal energy from the combustion of fuel into the kinetic energy of the twisting motion.
It's important to know! The main indicator M of the engine is the maximum torque.
It is the torque that creates the thrust force of the motor. The higher this indicator, the more M of the unit.
In our country, M power units are calculated in horsepower. All over the world there is a tendency to calculate M in W. Now the power characteristic is indicated in the documentation in two dimensions at once in hp. and kilowatts. In which unit to measure M is determined by the manufacturer of power electrical and mechanical installations.
M electricity
Electric M is characterized by the conversion speed electrical energy into mechanical, thermal or light energy. According to the International System of SI, watt is this UIM, in what is measured full power electricity.
How is power measured?
- N = A / t
Power is the amount of work done per unit of time. those. measured in joules per second. In the international system of measurement, this unit is called Watt, abbreviated as W. Well, derivatives from not kW, mW, etc.
Engine power is still commonly measured in horsepower, although traditional power must be indicated in office documents
Power in physics in SI units is measured in watts (W), after the author's surname is Watt. The most general formula to calculate the power N is as follows: N = A / t, where And what work was done (performed) and t is the time during which this work was done. In other words, from here we can give a definition of what power is. This is work done per unit of time. Work is expressed in joules (J) and time in seconds (s). The specific formula for calculating the power depends on which branch of physics the problem is set from. For example, the power of an electric current is calculated by the formula N = UI, where U is the voltage (in volts V), I is the current (in amperes A).
One of the physical quantities is called power
In physics lessons they constantly talk about it, they write in textbooks
Watt- this is how power is measured
This must be remembered and learned - this knowledge can still be useful.
Well, we must agree that the power is different.
Power is measured in watts in si system (watt). It is more customary for power engineers to measure power in kilowatts (kW), or megawatts (MW). W is joule / second. That is, power in other words is work or energy per unit of time.
Power is a physical quantity. Exists different types power - power in mechanics, electrical power.
In SI units, the unit of measure for power is the watt, which is equal to one joule divided by the second, or horsepower.
Power units: 1 watt, 1 kilowatt, megawatt, 1 kilogram-force meter per second, 1 erg, 1 horsepower.
I can only tell by household appliances. Power, for example, household appliances(hair dryers, irons, etc.) is measured in watts. Watt in Russian is denoted W and they measure power in the International System of Units.
If in this case we mean a physical quantity, which is generally equal to the ratio of the work that was performed in a specific time to this very period of time, then it is measured in watts, the designation in the international system is W, in Russian - W. By the way, the unit of measurement is named in honor of James Watt (Watt), who in his time invented the steam engine.
Watching the power of what. Power electric motor measured in watts, kilowatts.
Vehicle engine power is measured in horsepower.
Work is measured in joules and kilojoules.
Power is a physical quantity. And it is equal to the work that has been done in a certain period of time. As a consequence, the formula for determining power (in physics it is denoted by the letter N) looks like this:
where A is the work performed (the unit of measure for this work is Joule), and t is the time during which this work was performed (measuring time in seconds).
This means that Watt is Joule / second.
Power can be different active, reactive, full I'm talking about electrical active is measured in vars, reactive in watts, and full in kilovolt amperes, there is also engine power, it is measured in horsepower.