Energy is a quantitative property that can be transferred from one and different objects in order for it to perform work. Joule is the SI unit for energy, which is a scalar quantity. You've probably heard about energy a hundred times from your teacher, but have you ever wondered what kind of work is required to define energy? When an object is moved against a force, such as gravity, then the work is done by the gravity.
Checkout Important Question: What are the five types of energy?
Definition Of Energy
In physics, energy is the capacity to do work. It can be potential, kinetic, thermal, electrical, chemical, nuclear, or in other forms. There is also heat and work, which are both examples of energy in the process of being transferred from one body to another. Energy is always designated according to its nature after it has been transferred. As a result, heat transferred may become thermal energy, whereas work done may manifest as mechanical energy.
Read more : Unit of Time
Unit for Energy
“Joule” is the unit of measurement for energy all around the world, as it was chosen as the S.I unit by The International System of Units. Joule is a derived unit that is equal to the one-newton force applied over one meter of distance and the resulting energy is the number of Joules. However all around the world, people use various different local units for energy. Some of them are calories, ergs, British Thermal Units, kilocalories and kilowatt-hours. These kinds of units require a conversion factor to convert them to the S.I unit “Joule”.
Read more : Joule Thomson Effect
Conversion of Energy
Energy can be transferred through objects for their utilisation. So, when energy transfers through objects the term used for the transfer is called Energy Transfer. There are various kinds of transformations of energy that we do or do not notice around us in the world.
Read more : Dimentional Analysis
There are four ways through which energy can be transferred through objects.
- Electrically – Through Electricity
- Mechanically – By direct contact or by applying Force
- By Heating – By Radiation, convection, or Conduction
- By Radiation – By waves to sound or waves of light waves
The Law for Conservation of Energy
The law of conservation of energy sees over the motion of individual atoms in a chemical reaction. According to The law of conservation of energy, “In a closed system, the total energy of the system remains conserved.” So, the total energy in a system will stay the same while the energy is transformed. So, Energy can never be created or destroyed, it is only be converted from one form to another.
Types Of Energy
There are various kinds of energy, namely, they are:
- Electrical Energy
- Solar Energy
- Thermal Energy
- Wind Energy
- Light Energy
- Nuclear Energy
- Green Energy
- Tidal Energy
- Wave Energy
- Biomass Energy
- Heat Energy
- Kinetic Energy
- Hydroelectric Energy
- Geothermal Energy
Energy, however, can be generally categorised into these two forms.
- Kinetic Energy
- Potential Energy
Kinetic Energy
- Kinetic energy is the energy associated with the movement of an object.
- Objects that Move can cause changes and hence do work. To better understand it, think of a destructive ball. Moving wreck balls are used for work such as the demolition of buildings and stones. Even a slow-moving ball can do a lot of damage to other objects, such as an empty house. However, a stationary destruction ball will not work. So kinetic energy is found in objects that are in motion.
- Another example of kinetic energy is the energy associated with the constant random reflection of an atom or molecule. This is also known as thermal energy. The average thermal energy of a group of molecules is called temperature, and when thermal energy is transferred between two objects, it is known as heat.
- The kinetic energy can be calculated by using the equation K.E= ½ mv². Here, V is the velocity of the object and m is the mass of the object.
- The different kinds of kinetic energy are Radiant Energy, Thermal Energy, Sound Energy, Electrical Energy and Mechanical Energy.
Potential Energy
- Potential energy is the type of energy that is stored in an object and its intensity depends on the height at which the object is placed. This energy, along with kinetic energy, is one of two major forms of energy.
- The potential energy equation is given by mgh.
- Where "m" is the mass of the object in kilograms, "g" is the acceleration due to gravity, and "h" is the height in meters.
- The various kinds of Potential Energy are Gravitational Potential Energy, Elastic Potential Energy, Chemical Potential Energy and Electric Potential Energy.
Things To Remember based on Energy and Classification Of Energy
- Energy is a quantitative property that can be transferred from one and different objects in order for it to perform work.
- “Joule” is the unit of measurement for energy all around the world, as it was chosen as the S.I unit by The International System of Units.
- Energy can be transferred through objects for their utilisation. So, when energy transfers through objects the term used for the transfer is called Energy Transfer.
- Kinetic energy is the energy that is in motion. For instance, a moving ball, flowing water, and so on.
- The kinetic energy can be calculated by using the equation K.E= ½ mv². Here, V is the velocity of the object and m is the mass of the object.
- Where "m" is the mass of the object in kilograms, "g" is the acceleration due to gravity, and "h" is the height in meter
- The amount of work done is used to calculate the amount of energy stored in an object is known as potential energy. The potential energy equation is given by mgh.
Important Questions based on Energy and Classification Of Energy
Ques : What is the total energy of an object that freely falls to the ground? ( 1 Mark)
Ans: When an object falls freely to the ground the total energy of the object remains constant.
Ques: What happens to the energy of the body you work in? ( 1 Mark)
Ans: When energy is in the body, the more we work, the body gets more energy.
Ques : What is an Energy's Commercial Unit? ( 1 Mark)
Ans: The unit used for commercial use, like in big industries or mass consumers of energy, the unit of energy used is mentioned in kilowatt-hours.
Read more : Gravitational Potential Energy
Ques: What is a good energy source? ( 1 Mark)
Ans: An energy source is a source that can provide sufficient usable energy for a long period of time at a constant rate.
Ques : Can one store energy? ( 2 Marks)
Ans: Yes, you can store energy. An effective way to store energy is to take the form of chemical energy in the battery. When connected to a circuit, the energy stored in the battery is released to generate electricity. Energy can also be stored in many other ways. Batteries, petrol, natural gas, food, water towers, exciting alarm clocks, hot water thermos, all energy stores.
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Ques : Define the term gravitational energy? ( 2 Marks)
Ans:Gravitational energy is the energy associated with gravity. The following expressions indicate that gravitational energy is also used to move along the track. The system can also increase gravitational energy as the mass moves away from the centre of the Earth or other objects such as planets, suns, stars, etc., which remain large enough to generate large amounts of gravity.
Ques: Where does the energy come from? ( 2 Marks)
Ans: According to the law of conservation of energy, "energy is not produced or destroyed, but it can be changed from one standard form to another."
The energy we use is simply another form of conversion. There are no specific resources. But most of the energy we use is the result or product of the sun.
Ques: Is thermal energy renewable or non-renewable? Why is that so? ( 2 Marks)
Ans: Thermal energy is renewable if it comes from the sun. When obtained from diesel, thermal energy is not renewable. Thermal energy is renewable when supplied from biodiesel.
Read more : Unit of Force
Ques: An object of mass 0.4kg moving with a velocity of 4m/s collides with another object of mass 0.6kg moving in the same direction with a velocity of 2m/s. If the collision is perfectly inelastic, what is the loss of K.E. due to impact? (5 Marks)
Ans: In the ?b?ve questi?n it is given th?t:
m1 = 0.4kg,
u1 = 4m/s,
m2 = 0.6kg
?nd
u2 = 2m/s
T?t?l K.E. before collision is given by:
Ki=12m1u12+12m2u22
⇒Ki=12(0.4)(4)2+12(0.6)(2)2
⇒Ki=4.4J
Since collision is perfectly inel?sti?,
v=m1u1+m2u2m1+m2=2.8m/s
T?t?l K.E. ?fter ??llisi?n is given by:
Kf=12(m1+m2)v2
⇒Kf=12(0.4+0.6)2.82
⇒Kf=3.92J
Thus, l?ss in K.E. will be:
ΔK=Ki−Kf
⇒ΔK=4.4−3.92=0.48J
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