# Energy & Power

**1. Energy and Power**

-By definition, the capacity of a physical system to perform work is called Energy. Energy has many forms and is transferable from one object to another in the same form or different.

-By definition, the rate at which work is performed is called Power. Power is the amount of energy per unit time.

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Mathematically, it can be said that energy is power integrated over time and similarly, power is time derivative of energy.

**2. Measuring Energy & Power**

Energy cannot be measured directly. Theoretically, energy can be measured in terms of work, since work can be defined. Power, on the other hand, can be measured by calculating energy consumed per unit. In practicality, while measuring power, dissipated power should also be accounted for.

**3. Units of Energy and Power ?**

Standardised quantity used to measure, refer or compare are called units. Like everything else, energy and power have universally used units.

-Energy is usually measured in terms of calories, joules etc.

-Power is usually measured in terms of watts, horsepower etc.

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