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**Electrical Engineering ⇒ Topic : Power and Energy**

Definition of Power and Energy |

Sonali
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Energy is the capacity for doing work, i.e. energy is nothing but stored work. Energy
may exist in many forms such as mechanical, chemical, electrical and so on. Power
is the rate of change of energy, and is denoted by either P or p. If certain amount of
energy is used over a certain length of time, then
dw is the change in energy and dt is the change in time.We can also write p = dw/dt = dw/dq X dq/dt | |||||||||

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Maninder
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To transfer a charge through an element, work is done. To determine the energy being supplied to the element or by the element to the rest of the circuit, we should know both the polarity of the voltage across the element and the direction of the current through the element. If a positive current enters the positive terminal of an element, an external force must drive the current. Therefore, the external force delivers energy to the element. On the other hand, if the current leaves the positive terminal or enters the negative terminal, the element is delivering energy to the external circuit. In Figures (a) and (b), the element is absorbing energy whereas in Figures (c) and (d), the element is delivering energy.Different voltage-current relationships. | |||||||||

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Arundeep
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Power : | |||||||||

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Dynmo
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Power is the rate of doing work. The unit of power is watt whose symbol is W.In practice, the unit watt is often found to be inconveniently small and so the kilo watt (kW) or megawatt (MW) is frequently used
Energy is defined as the ability to perform work. In electricity, the total amount of energy spent is the rate at which work is done, multiplied by the time during which work is done. That is,
If V is in volts, I is in amperes and t is in hours, then energy E will be in watt hours. If the amount of energy is large, it is often expressed in kilo watt hours (kWh) or in megawatt hours (MWh) | |||||||||

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