Electric power: Difference between revisions
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<onlyinclude>'''Electric power''' is a transfer of [[energy]] over time | [[File:Incandescent Light Bulb.png|thumbnail|250px|right|Figure 1. A typical incandescent light bulb. The filament is the thin wire stretched between the vertical contact wires and held up by two other support wires. The electric power is given by the electric current times the voltage drop across the light bulb.]] | ||
<onlyinclude>'''Electric power''' is a transfer of [[energy]] over time (just like un-prefixed [[power]]), however, it specifically refers to energy transfer in the form of [[electricity]], sending [[electric current]] through [[conductor]]s. </onlyinclude> | |||
'''Power = Current x Voltage''' | '''Power = [[Current]] x [[Voltage]]''' | ||
[[Power]] tools, vacuum cleaners, and wall chargers all have an "[[ampere|amps]]" rating on them. The [[amperage]] (A) of a normally operating industrial circular saw is 15 A. With this amperage rating, it is possible to determine the total power output of the tool, simply by multiplying the amperage by the [[voltage]] of the current it is drawing. For example, running a 15 A circular saw off of a 120 V [[circuit]] would lead to a power draw of 1800 [[watt]]s (W). | [[Power]] tools, vacuum cleaners, and wall chargers all have an "[[ampere|amps]]" rating on them. The [[amperage]] (A) of a normally operating industrial circular saw is 15 A. With this amperage rating, it is possible to determine the total power output of the tool, simply by multiplying the amperage by the [[voltage]] of the current it is drawing. For example, running a 15 A circular saw off of a 120 V [[circuit]] would lead to a power draw of 1800 [[watt]]s (W). | ||
==Power== | ==Power== | ||
Electric power is how fast an electrical component, [[circuit]] or system uses [[energy]]. | Electric power is how fast an electrical component, [[electric circuit]] or system uses [[energy]]. | ||
*Power units are the [[Watt]] (W), 1 watt is equivalent to 1 [[Joule]]/[[second]] (J/s). | *Power units are the [[Watt]] (W), 1 watt is equivalent to 1 [[Joule]]/[[second]] (J/s). | ||
The following relationship emerges between power, [[current]] and applied [[voltage]] | The following relationship emerges between power, [[current]] and applied [[voltage]]: | ||
<math>P=IV</math> | |||
Where <math>P</math> is the power, <math>I</math> is the circuit current and <math>V</math> is the voltage change across the component. With the help of [[Ohm's law]] the power equation can be manipulated to be put in terms of different variables as described in the table below.<ref name=B>R.T. Paynter, “Basic Electric Components and Meters,” in ''Introduction to Electricity'', 1rst ed. NJ: Prentice-Hall, 2011, ch. 4, sec. 4.2, pp. 144-154.</ref> | |||
{| class="wikitable" | {| class="wikitable" | ||
|- | |- | ||
! In terms of !! Formula | ! In terms of !! Formula | ||
|- | |- | ||
| circuit current and applied voltage || | | circuit current and applied voltage || <math>P=IV</math> | ||
|- | |- | ||
| circuit current and circuit [[resistance]] || | | circuit current and circuit [[resistance]] || <math>P=I^2R</math> | ||
|- | |- | ||
| applied voltage and resistance || | | applied voltage and resistance || <math>P=\frac{V^2}{R}</math> | ||
|} | |} | ||
| Line 28: | Line 31: | ||
===Power rating=== | ===Power rating=== | ||
The power rating is the maximum rate at which an electronic device (for example a [[transducer]]) can convert energy into [[energy#Types of energy|some other form]], similar to [[ampacity]] for electric current. Any device which is capable of converting one form of energy to another is referred to as a transducer. For example, resistors have the ability to absorb energy and transform it into heat | The power rating is the maximum rate at which an electronic device (for example a [[transducer]]) can convert energy into [[energy#Types of energy|some other form]], similar to [[ampacity]] for electric current. Any device which is capable of converting one form of energy to another is referred to as a transducer. For example, resistors have the ability to absorb energy and transform it into heat. The rate at which it absorbs energy must be equal to the rate at which it dissipates heat. If the rate at which the resistor absorbs heat is exceeded the resistor will melt, and be destroyed. The power rating for the resistor thus describes its ability to dissipate heat. | ||
===Power efficiency=== | ===Power efficiency=== | ||
The power [[efficiency]] of a device is a measure of how well that device converts [[electricity]] into [[work]]. [[Electric motor]]s have extremely high power efficiency, usually over 90%, and often exceeding 96%. This is in stark contrast to [[internal combustion engine]]s, which have an efficiency of between 25% and 35%. This discrepancy in efficiency is why [[electric vehicle]]s achieve such high [[miles per gallon gasoline equivalent|MPGe]] ratings. This is also why electricity is considered to be [[energy quality|higher quality energy]]. | The power [[efficiency]] of a device is a measure of how well that device converts [[electricity]] into [[work]]. [[Electric motor]]s have extremely high power efficiency, usually over 90%, and often exceeding 96%. This is in stark contrast to [[internal combustion engine]]s, which have an efficiency of between 25% and 35%. This discrepancy in efficiency is why [[electric vehicle]]s achieve such high [[miles per gallon gasoline equivalent|MPGe]] ratings. This is also why electricity is considered to be [[energy quality|higher quality energy]]. | ||
Power efficiency cannot exceed 100% because energy cannot be created or destroyed as stated in the [[ | Power efficiency cannot exceed 100% because energy cannot be created or destroyed as stated in the [[First law of thermodynamics]]. | ||
== For Further Reading == | |||
For further information please see the related pages below: | |||
*[[Direct current]] | |||
*[[Electricity]] | |||
*[[Electrical grid]] | |||
*[[Electric generator]] | |||
* Or explore a [[Special:Random| random page!]] | |||
==References== | ==References== | ||
{{reflist}} | {{reflist}} | ||
[[Category:Uploaded]] | [[Category:Uploaded]] | ||
Latest revision as of 22:53, 18 May 2018
Electric power is a transfer of energy over time (just like un-prefixed power), however, it specifically refers to energy transfer in the form of electricity, sending electric current through conductors.
Power tools, vacuum cleaners, and wall chargers all have an "amps" rating on them. The amperage (A) of a normally operating industrial circular saw is 15 A. With this amperage rating, it is possible to determine the total power output of the tool, simply by multiplying the amperage by the voltage of the current it is drawing. For example, running a 15 A circular saw off of a 120 V circuit would lead to a power draw of 1800 watts (W).
Power
Electric power is how fast an electrical component, electric circuit or system uses energy.
The following relationship emerges between power, current and applied voltage:
Where is the power, is the circuit current and is the voltage change across the component. With the help of Ohm's law the power equation can be manipulated to be put in terms of different variables as described in the table below.[1]
| In terms of | Formula |
|---|---|
| circuit current and applied voltage | |
| circuit current and circuit resistance | |
| applied voltage and resistance |
The power rating is crucial in electrical applications especially to transducers.
Power rating
The power rating is the maximum rate at which an electronic device (for example a transducer) can convert energy into some other form, similar to ampacity for electric current. Any device which is capable of converting one form of energy to another is referred to as a transducer. For example, resistors have the ability to absorb energy and transform it into heat. The rate at which it absorbs energy must be equal to the rate at which it dissipates heat. If the rate at which the resistor absorbs heat is exceeded the resistor will melt, and be destroyed. The power rating for the resistor thus describes its ability to dissipate heat.
Power efficiency
The power efficiency of a device is a measure of how well that device converts electricity into work. Electric motors have extremely high power efficiency, usually over 90%, and often exceeding 96%. This is in stark contrast to internal combustion engines, which have an efficiency of between 25% and 35%. This discrepancy in efficiency is why electric vehicles achieve such high MPGe ratings. This is also why electricity is considered to be higher quality energy.
Power efficiency cannot exceed 100% because energy cannot be created or destroyed as stated in the First law of thermodynamics.
For Further Reading
For further information please see the related pages below:
References
- ↑ R.T. Paynter, “Basic Electric Components and Meters,” in Introduction to Electricity, 1rst ed. NJ: Prentice-Hall, 2011, ch. 4, sec. 4.2, pp. 144-154.