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Examples of power

Examples of power are limited only by the imagination, because there are as many types as there are forms of work and energy. (See [link] for some examples.) Sunlight reaching Earth’s surface carries a maximum power of about 1.3 kilowatts per square meter ( kW/m 2 ) . size 12{ \( "kW/m" rSup { size 8{2} } \) "." } {} A tiny fraction of this is retained by Earth over the long term. Our consumption rate of fossil fuels is far greater than the rate at which they are stored, so it is inevitable that they will be depleted. Power implies that energy is transferred, perhaps changing form. It is never possible to change one form completely into another without losing some of it as thermal energy. For example, a 60-W incandescent bulb converts only 5 W of electrical power to light, with 55 W dissipating into thermal energy. Furthermore, the typical electric power plant converts only 35 to 40% of its fuel into electricity. The remainder becomes a huge amount of thermal energy that must be dispersed as heat transfer, as rapidly as it is created. A coal-fired power plant may produce 1000 megawatts; 1 megawatt (MW) is 10 6 W size 12{"10" rSup { size 8{6} } " W"} {} of electric power. But the power plant consumes chemical energy at a rate of about 2500 MW, creating heat transfer to the surroundings at a rate of 1500 MW. (See [link] .)

A distant view of a coal-fired power plant with clearly visible cooling towers generating electric power and emitting a large amount of gases.
Tremendous amounts of electric power are generated by coal-fired power plants such as this one in China, but an even larger amount of power goes into heat transfer to the surroundings. The large cooling towers here are needed to transfer heat as rapidly as it is produced. The transfer of heat is not unique to coal plants but is an unavoidable consequence of generating electric power from any fuel—nuclear, coal, oil, natural gas, or the like. (credit: Kleinolive, Wikimedia Commons)
Power output or consumption
Object or Phenomenon Power in Watts
Supernova (at peak) 5 × 10 37 size 12{5 times "10" rSup { size 8{"37"} } } {}
Milky Way galaxy 10 37 size 12{"10" rSup { size 8{"37"} } } {}
Crab Nebula pulsar 10 28 size 12{"10" rSup { size 8{"28"} } } {}
The Sun 4 × 10 26 size 12{4 times "10" rSup { size 8{"26"} } } {}
Volcanic eruption (maximum) 4 × 10 15 size 12{4 times "10" rSup { size 8{"15"} } } {}
Lightning bolt 2 × 10 12 size 12{2 times "10" rSup { size 8{"12"} } } {}
Nuclear power plant (total electric and heat transfer) 3 × 10 9 size 12{3 times "10" rSup { size 8{9} } } {}
Aircraft carrier (total useful and heat transfer) 10 8 size 12{"10" rSup { size 8{8} } } {}
Dragster (total useful and heat transfer) 2 × 10 6 size 12{2 times "10" rSup { size 8{6} } } {}
Car (total useful and heat transfer) 8 × 10 4 size 12{8 times "10" rSup { size 8{4} } } {}
Football player (total useful and heat transfer) 5 × 10 3 size 12{5 times "10" rSup { size 8{3} } } {}
Clothes dryer 4 × 10 3 size 12{4 times "10" rSup { size 8{3} } } {}
Person at rest (all heat transfer) 100 size 12{"100"} {}
Typical incandescent light bulb (total useful and heat transfer) 60 size 12{"60"} {}
Heart, person at rest (total useful and heat transfer) 8 size 12{8} {}
Electric clock 3 size 12{3} {}
Pocket calculator 10 3 size 12{"10" rSup { size 8{-3} } } {}

Power and energy consumption

We usually have to pay for the energy we use. It is interesting and easy to estimate the cost of energy for an electrical appliance if its power consumption rate and time used are known. The higher the power consumption rate and the longer the appliance is used, the greater the cost of that appliance. The power consumption rate is P = W / t = E / t size 12{P= {W} slash {t} = {E} slash {t} } {} , where E size 12{E} {} is the energy supplied by the electricity company. So the energy consumed over a time t size 12{t} {} is

E = Pt. size 12{E= ital "Pt"} {}

Electricity bills state the energy used in units of kilowatt-hours ( kW h ) , size 12{ \( "kW" cdot h \) ,} {} which is the product of power in kilowatts and time in hours. This unit is convenient because electrical power consumption at the kilowatt level for hours at a time is typical.

Questions & Answers

material that allows electric current to pass through
Deng Reply
material which don't allow electric current is called
Deng
insulators
Covenant
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Ewa Reply
what is conservative force with examples
Moses
what is work
Fredrick Reply
the transfer of energy by a force that causes an object to be displaced; the product of the component of the force in the direction of the displacement and the magnitude of the displacement
AI-Robot
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Esther Reply
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Esther
Is the ship moving at a constant velocity?
Kamogelo Reply
The full note of modern physics
aluet Reply
introduction to applications of nuclear physics
aluet Reply
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Moses Reply
I need more explanation or all about kinematics
Moses
yes
zephaniah
I need more explanation or all about nuclear physics
aluet
Show that the equal masses particles emarge from collision at right angle by making explicit used of fact that momentum is a vector quantity
Muhammad Reply
yh
Isaac
A wave is described by the function D(x,t)=(1.6cm) sin[(1.2cm^-1(x+6.8cm/st] what are:a.Amplitude b. wavelength c. wave number d. frequency e. period f. velocity of speed.
Majok Reply
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Somto Reply
A body is projected upward at an angle 45° 18minutes with the horizontal with an initial speed of 40km per second. In hoe many seconds will the body reach the ground then how far from the point of projection will it strike. At what angle will the horizontal will strike
Gufraan Reply
Suppose hydrogen and oxygen are diffusing through air. A small amount of each is released simultaneously. How much time passes before the hydrogen is 1.00 s ahead of the oxygen? Such differences in arrival times are used as an analytical tool in gas chromatography.
Ezekiel Reply
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Samuel
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the science concerned with describing the interactions of energy, matter, space, and time; it is especially interested in what fundamental mechanisms underlie every phenomenon
AI-Robot
Practice Key Terms 4

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Source:  OpenStax, College physics. OpenStax CNX. Jul 27, 2015 Download for free at http://legacy.cnx.org/content/col11406/1.9
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