Power is how fast power is reinvented or transmitted. To do an analogy: if power is prefer money, strength is a fairy or salary (e.g., $18/hour or $50,000/year), or usage rate (e.g, security $20/hour to rental a canoe or $1500/month ~ above rent).

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Power have the right to be expressed in countless different units, all of which have the right to be expressed as a unit the energy split by a unit the time. The most usual unit is the watt (W), characterized as 1 joule (J) of energy per second. A 40 W light bulb, then, offers 40 J of electric energy every 2nd to continue to be lit.<1> The mean power output of the human body during moderate practice is about 100 W.<2>

For many engines and power tree there space two different powers. The price at which energy is coming into the device from the fuel is the thermal power. The lot of power that the engine is outputting is the mechanically power. Because that a strength plant, this output is electrical power so it"s measured in megawatts electric (MWe) together opposed come the input power which is measure up in megawatts thermal (MWt).


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Energy and Power

The relationship in between power, energy, and time have the right to be described by the complying with equation<1>:

P = \frac\Delta E_sys\Delta tP is the mean power output, measure in watt (W)Δt is the expression - exactly how long the power use take away - measure up in secs (s)

Since strength is a price of power use (energy split by an interval that time), multiply a unit of strength by a unit the time will offer a amount of energy. One such example is in the energy unit kilowatt-hours (kWh). A kilowatt is equal to 1000 watts, therefore 1 kWh to represent the quantity of power transfer that occurs over one hour indigenous a power output of 1000 watt (i.e., joules every second). Hence 1 kWh is equal to 3,600,000 joules of power transfer (work).

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More power can attain a job with a given power requirement in a shorter time. Because that example, lifting a 15 kg block 2 meters in the air. This task requires roughly 300 J of power input (work). A motor and pulley device with a 5 W power output could accomplish this job in one minute. However, a more powerful motor through an calculation of 100 W could raise the box to the same elevation in simply three seconds! yet in the end, both electric motors will have done the same amount of job-related (energy transfer) in lifting the box.

Power outputtimeTotal energy transfer
5 W60 s300 J
100W3 s300 J

Power Unit Conversion

Please see listed below to convert among various units for power: