Power And Energy

Power And Energy

We often consider Power and Energy to be the same as synonyms. Energy and power are said to be closely related but not the same type of physical quantities. Though, they are used in everyday life the difference between them is fine, but significant.

Energy is known as the capacity to do some physical activities or work such as running, jumping, etc while the power is defined as the rate at which the energy is transferred or the work is completed. The unit used to measure energy is Joules, ergs, calories. Power is measured in Watts, wherein other terms it is ergs per second or even Joules per second.

Let us consider the example of a weightlifter in order to understand the concept of Energy and Power in a more precise manner. Power is something like strength of weightlifter, whereas the Energy is said to be the measure of how long he could sustain that output of power. Energy is ‘joules’ and  power is the ‘joules per second’.  

Energy changes from one form to another, but not the power. If there is something that has to happen, Energy is said to change its form. Power is known only to measure as to how fast the change has occurred; in other words, Power is defined as the rate at which energy converts every second.

Difference between Energy and Power

Sr.no Energy Power
1. Energy is defined as the capacity to do some work. It is power which is integrated over time. Power is defined as the rate at which a specific work is done, or which the energy is transmitted.
2. The unit used to measure energy is joules or watt-seconds The unit used to measure this is watt or joules per second
3. ‘W’ is the symbol which denotes energy The symbol used to denote power is P.
4. Energy changes from one form to another Power cannot be transformed from one type to another
5. Energy is a time quantity or component It is an instantaneous quantity
6. Various types of energy are kinetic, thermal, potential, gravitational, sound, electromagnetic, light, elastic, etc Different kinds of power are electric power, optical power, human power, etc.
7. Energy is known to be stored which can be used in future Power quantity is not storable or cannot be stored
8. energy is used in moving a car, heating home, lighting night, flying an aeroplane, etc Power finds its uses in mechanical applications, electrical applications,heat applications, etc

Practise This Question

A reversible engine converts one-sixth of the heat input into work. When the temperature of the sink is reduced by 62C, the efficiency of the engine is doubled. The temperatures of the source and sink are