Energy is one of most fundamental concepts in science. In fact, all known phenomena involve some form of energy. Energy comes in several different forms such as chemical energy, thermal energy, nuclear energy, radiation energy, magnetic energy etc. However in terms of motion of the two objects, the energy is categorized into two types namely; Kinetic Energy and Potential Energy. One of the key characteristics of energy is that it is conserved which means it just does not disappear though it can change form i-e it can be converted from kinetic energy to potential energy and otherwise.
The basic unit of energy as defined by System International (SI) is joule (J).
1 J = 1 kg.m2.s-2
Different units of energy
However there exists a wide variety of units in which quantity of energy is defined. For example, when we are dealing with electricity we often use kilowatt hour (kWh). If you eat a chocolate and wants to know how much energy have you consumed, check out the chocolate wrap and you will find somewhere the amount of energy that chocolate has in terms of calorie (c) or kilo calorie (C or kcal). Similarly when we are dealing with the energies of atomic particles, we measure their energy in terms of electron-volt (eV).
How much is 1 Joule?
In order to get an idea, how much is one joule of energy, consider an apple of roughly 0.1 kg. Now assume that you have to lift that apple upward at the height of 1 meter. In that case, we have to perform work against the gravity, so let’s calculate the energy required for apple to be lifted at height of 1 meter using the expression for potential energy.
Mass of apple (m) = 0.1 kg
Height at which the apple to be lifted (h) = 1 m
Acceleration due to gravity (g) = 9.81 m.s-2 = 10 m.s-2
As we know the potential energy due to acceleration due to gravity is given as
Potential Energy = mgh
So by inserting the given information, we found the amount of energy as
Potential Energy = (0.1)(10)(1) kg. m2.s-2 = 1 J
Hence 1 Joule of energy is roughly equal to the energy required to lift an apple at a height of a about 1 m.
As now, you get an idea of how much 1 Joule of energy is, let’s see how it relates to other units of energy:
1 btu = 1055.06 J
1 calorie = 4.18 J
1 kWh = 3,600,000 J
1 eV = 1.602 x 10-19 J
As you can see from above that 1 kWh is much larger unit of energy whereas 1 eV is an extremely small unit of energy.
1 thought on “Understanding how much Energy is contained in 1 joule?”