Explain law of conservation of energy? And also commercial unit of energy?
The law of conservation of energy states that energy can neither be created nor be destroyed. It may be transferred from one of its forms to the other. But the total energy of an isolated system always remains constant, if you take into account all forms of energy.
The SI unit joule is too small to express very large quantities of energy. Hence we use a bigger unit called kilowatt hour (kWh) to express energy. 1 kWh is the amount of energy consumed by an electrical gadget in one hour at the rate of 1000 J/s or 1kW.
Proof for Law of Conservation of Energy: Considering the potential energy at the surface of the earth to be zero.
At point A, the velocity of the ball is zero hence only potential energy is there.
E = mgH ———- (1)
At point B, the ball is falling freely under gravity so it will gain 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 third equation of motion,
v^2=2g(H–X)⇒1/2mv^2=1/2m.2g(H–X)⇒K.E=1/2m.2g(H–X)⇒K.E=mg(H–X) ——– (3)
Using (1), (2) and (3)
E = mg(H – X) + mgX
E = mg(H – X + X)
E = mgH
Similarly if we energy at point C it will come out to be mgH. We can see as the ball is coming down the total energy remains constant, only potential energy is getting converted into kinetic energy. So there must be a point where kinetic energy becomes equal to potential energy. Suppose we need to find that height ‘x’ from the ground. We know that at that point,
K.E = P.E
=> P.E = K.E = E2 ——– (4)
Where, E = mgH
As the body is at height X from the ground,
P.E = mgX ——— (5)
Using (4) and (5) we get,
mgX=mgH2⇒X=H2
Energy Conservation: Energy conservation is not about making limited resources last as long as they can, that would mean that you are doing nothing more than prolong a crisis until you finally run out of energy resources all together. Conservation is the process of reducing demand on a limited supply and enabling that supply to begin to rebuild itself. Many times the best way of doing this is to replace the energy used with an alternate.
Examples: In physics, most of the inventions rely 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 law of conservation of energy. We will discuss a few examples here.
- In a torch, the chemical energy of the batteries is converted into electrical energy, which is converted into light and heat energy.
- 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.
- In a loudspeaker, electrical energy is converted into sound energy.
- In a microphone, sound energy is converted into electrical energy.
- In a generator, mechanical energy is converted into electrical energy.
- When fuels are burnt, chemical energy is converted into heat and light energy.
- Chemical energy from food is converted to thermal energy when it is broken down in the body and is used to keep it warm.
The SI unit joule is too small to express very large quantities of energy. Hence we use a bigger unit called kilowatt hour (kWh) to express energy. 1 kWh is the amount of energy consumed by an electrical gadget in one hour at the rate of 1000 J/s or 1kW.
Proof for Law of Conservation of Energy:
Considering the potential energy at the surface of the earth to be zero.
At point A, the velocity of the ball is zero hence only potential energy is there.
E = mgH ———- (1)
At point B, the ball is falling freely under gravity so it will gain 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 third equation of motion,
v^2=2g(H–X)⇒1/2mv^2=1/2m.2g(H–X)⇒K.E=1/2m.2g(H–X)⇒K.E=mg(H–X) ——– (3)
Using (1), (2) and (3)
E = mg(H – X) + mgX
E = mg(H – X + X)
E = mgH
Similarly if we energy at point C it will come out to be mgH. We can see as the ball is coming down the total energy remains constant, only potential energy is getting converted into kinetic energy. So there must be a point where kinetic energy becomes equal to potential energy. Suppose we need to find that height ‘x’ from the ground. We know that at that point,
K.E = P.E
=> P.E = K.E = E2 ——– (4)
Where, E = mgH
As the body is at height X from the ground,
P.E = mgX ——— (5)
Using (4) and (5) we get,
mgX=mgH2⇒X=H2
Energy Conservation:Energy conservation is not about making limited resources last as long as they can, that would mean that you are doing nothing more than prolong a crisis until you finally run out of energy resources all together. Conservation is the process of reducing demand on a limited supply and enabling that supply to begin to rebuild itself. Many times the best way of doing this is to replace the energy used with an alternate.
Examples:In physics, most of the inventions rely 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 law of conservation of energy. We will discuss a few examples here.
- In a torch, the chemical energy of the batteries is converted into electrical energy, which is converted into light and heat energy.
- 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.
- In a loudspeaker, electrical energy is converted into sound energy.
- In a microphone, sound energy is converted into electrical energy.
- In a generator, mechanical energy is converted into electrical energy.
- When fuels are burnt, chemical energy is converted into heat and light energy.
- Chemical energy from food is converted to thermal energy when it is broken down in the body and is used to keep it warm.
