What are Various Forms of Energy? Law of Conservation of Energy
Here we discussed Various Forms of Energy like Heat, Chemical, Electrical, Nuclear Energy, & Law of Conservation of Energy for NCERT School Classes.
What is Energy?
Energy can be referred to as the capacity to do work. There are various forms of energy such as heat energy, chemical energy, etc. Some forms of energy have been discussed in detail in this article.
Different forms of Energy
When a cup of hot coffee is left unattended for some time, you may find that the coffee gets cooled down. This is due to the heat lost to the surrounding which is at a lower temperature as compared to the coffee.
Heat energy is the form of energy which is derived from the total kinetic energy (KE) of the particles in an object. It is transferred because of a random motion of molecules that leads to them bouncing off each other and transferring energy during the process. Sometimes, it is also referred to as the energy in transit. Heat flows from a body of higher temperature (high total KE of the particles) to a body of lower temperature (low total KE of the particles).
Plants use solar energy, carbon dioxide (CO2), and water to synthesize food. This food is consumed by humans as well as by animals, gets broken down in their bodies, and they get the energy to perform life activities. These all are chemical energy examples.
Chemical energy is the energy that is contained in the bonds of chemical compounds. In addition, the chemically stable compound has less energy contained in it relative to its separate parts. When a chemical reaction occurs, there is a change in the arrangement of atoms resulting in either absorption (endothermic) or a release (exothermic) of energy.
The energy from moving electrical charges is called electrical energy. So when you turn on a torch, the chemical energy contained in batteries makes the charged particles flow from the low potential terminal to a high potential terminal. This electrical energy is used to light the torch that is transmitted to the surroundings as light energy.
You may be aware of the notorious bombings of the cities of Hiroshima and Nagasaki during World War Second, which caused damage to the extent that its effects can be seen even today. These were the nuclear bombs which have been considered to be one of the most dangerous creations of mankind to date.
The energy in the nucleus of an atom is Nuclear Energy. The energy can be emitted during nuclear fusion or fission reactions. And the energy released is really vast. It can be used to produce electricity when the reaction is controlled. Nuclear weapons are produced under uncontrolled nuclear fission reactions.
The Equivalence of Mass and Energy
An equation given by Einstein describes the relationship between the equivalence of mass and energy. According to him, the energy of a body is proportional to the mass of the body and the square of the speed of light. The famous equation is
E = mc2
Where E is the energy, m is the mass of the body and c is the speed of light in a vacuum which is approximately equal to 3 x 108 m/sec.
Law of Conservation of Energy
According to the law of conservation, energy can neither be created nor be destroyed; it may be converted from one form to another. If you take all sources of energy into account, the total energy of an isolated system always remains constant. All sources of energy are regulated by the law of conservation of energy. In other words, the law of conservation of energy states that
In a closed system, i.e., a system that is isolated from its surroundings, the total energy of the system is conserved.
So in an isolated system such as the universe, if there is a loss of energy in some part of it, there must be a gain of an equal amount of energy in some other part of the universe. Although this principle cannot be proved, there is no known example of a violation of the law of conservation of energy.
The following equation determines the amount of energy in any system:
UT = Ui + W + Q
U = W + Q
To determine the change in the internal energy of the system, use the equation
Law of Conservation of Energy Derivation
Consider the potential energy at the surface of the earth to be zero. Let us see an example of a fruit dropping from a tree.
Consider a point A, which is at height ‘H’ from the ground on the tree, the velocity of the fruit is zero, so there is full potential energy.
E= mgH———- (1)
When the fruit is falling, its potential energy is decreasing and kinetic energy is increasing.
At point B, which is near the bottom of the tree, the fruit is falling freely under gravity and is at a height X from the ground, and it has speed as it reaches point B. So, at this point, it will have both kinetic and potential energy.
E= K.E + P.E
P.E = mgX ——(2)
According to 3rd equation of motion,
V2 = 2g(H-X)
1/2 mv2 = 1/2 m.2g(H-X)
KE = 1/2 m.2g(H-X)
KE = mg(H-X)
KE = mg(H-X) —–(3)
Using (1), (2), and (3)
E = mg(H-X) + mgX
E = mg(H-X+X)
E = mgH
In the same way, if we see the energy at point C, which is at the bottom of the tree, it will become mgH. We can note that the fruit is falling to the bottom and here, potential energy (P.E) is getting converted into kinetic energy (K.E). So there must be a point where both P.E and K.E become equal. Suppose we want to get that height ‘x’ from the ground. We know at that point,
K.E = P.E
P.E = K.E =E/2 ——-(4)
E2 is the new energy
H2 is the new height.
As the body is at height X from the ground,
P.E =mgX ——— (5)
Using (4) and (5) we get,
mgX = mgH/2
X = H/2
H2 is referred to the new height
Energy conservation is not about limiting the use of resources that are finally going to run out. The ideal means of conservation would be to reduce demand for limited supply and allow that supply to begin to rebuild itself. Many times the best possible way of doing this is to replace the energy used with an alternative.
Law of Conservation of Energy Examples:
In Physics, most of the inventions are based on the fact that energy is conserved when it is transferred from one form to another. A number of electrical and mechanical devices operate solely on the basis of energy conservation law. Few examples have been discussed here.
i In a torch, the chemical energy of the batteries is converted into electrical energy, which is converted into light and heat energy.
ii. In hydroelectric power plants, waterfalls on the turbines from a height. This, in turn, rotates the turbines and generates electricity. Hence, the potential energy of water is converted into the kinetic energy of the turbine, which is further converted into electrical energy.
iii. In a loudspeaker, electrical energy is converted into sound energy.
iv. In a microphone, sound energy is converted into electrical energy.
v. In a generator, mechanical energy is converted into electrical energy.
vi. When fuels are burnt, chemical energy is converted into heat and light energy.
vii. Chemical energy from food is converted to thermal energy when it is broken down in the body and is used to keep it warm.
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