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What is Energy?

Energy is the ability to do work. This means the more a man works, the greater energy he possesses. The reverse is also true. Energy is a quantitative property that must be changed to another form to make our work easier.

Modern civilization came into existence because people learned to transform one form of energy into another. If we talk about a device like a generator, it converts mechanical energy into electrical. Energy exists in various forms in nature viz: kinetic, potential, thermal, electrical, nuclear, atomic, etc.

Here, we are going to discuss the different types of energy.

What is Energy in Physics?

Like work, energy is a scalar quantity. This means energy has magnitude but no direction.

The dimension of energy is the same as that of Work, i.e., [ML2T-2]. The unit of its measurement is Joule or J in the SI system and C.G.S (Centi-gram-second) system,  it is erg.

There are different practical units of energy holding a respective value equivalent to Joule; these are listed below:




Equivalent Value to Joule








4.2 J




3.6 x 106J




1.6 x 10-19J

Point to Note:

Energy is different from Power. It’s because energy is the ability to do maximum work, while power is the rate of doing work. Here, we can observe that power is the efficiency of a person to perform any task per unit of time; however, the maximum work he can do without considering the time constraint is the energy or we can say that for the energy, the time has no role.

There are many forms of energy existing in this universe viz: kinetic energy, potential energy, internal energy, magnetic energy, electrical energy, and so on. We will be focusing on common forms of energy followed by renewable and non-renewable energy.

What is Electrical Energy?

The energy generated by the movement of electrons from one point to another is called electrical energy. In simple words, the energy consumed in the form of electricity or electric power is called electrical energy. It is measured in Watt-seconds.

Electrical energy is an energy that can be transformed into another form to perform useful work. For example, an electric motor transforms electrical energy into mechanical.

What are the Sources of Energy?

Several resources help us lead our life comfortably. Energy resources are the resources that generate electricity, power our lives, produce heat, make, etc. There are two types of resources viz: renewable and nonrenewable resources. So, let’s discuss these one-by-one:

What are Renewable and Nonrenewable Resources?

The resources that are naturally occurring and can be replenished after their prolonged usage are renewable. These resources are naturally gifted to us by nature. Resources like wind, air, sunlight are all renewable.

These resources play their roles in the form of energy, that’s why we call them renewable energy, so do you know what is renewable energy? Let’s discuss its various forms:

  • Solar Energy: We obtain solar energy from sunlight. These days, we have made huge developments in utilizing solar energy, be it photovoltaics, molten solar powerpants, artificial photosynthesis, and so on.

The best part of this type of renewable energy is, it is free of cost. We can replace high power electrical appliances like geysers by using a solar water heater. We can stop the emission of harmful cooking gases like NO, CO by using a solar cooker.

  • Wind Energy: Wind energy is a form of solar energy that represents the process by which wind is utilized to produce electricity.

The wind rotates the propeller-like blades of a turbine around the rotor, which spins the generator. This, in turn, generates electricity.

  • Tidal Energy: Tidal energy can be viewed in the form of ocean tides. During high tides, this energy is utilized in rotating the turbine; this, in turn, generates electricity.

  • Geothermal Energy: Geothermal energy is the heat that is contained in the rock and fluid under the Earth’s crust. This energy can be used to heat structures viz: parking lots, sidewalks, etc.

Non-Renewable Energy

Non-renewable energy is a kind of energy that may run out if their over-usage is continued; also, they may take millions of years to re-form. Some of the types of nonrenewable energy are as follows:

  • Coal - It is extracted from the remains of plants that were buried under rocks a million years ago.

  • Oil - Oil can be extracted and refined to form products viz: petroleum, gasoline, jet fuel, etc.

  • Nuclear Energy - This is a form of energy released during nuclear reactions. This energy is used to generate heat, which is then used in steam turbines to produce electricity.

FAQ (Frequently Asked Questions)

Question 1: What are the Advantages of Tidal Energy?

Answer: Tidal energy is one of the most effective methods of electricity generation because ocean tides are naturally occurring events and emit no greenhouse gases; also, it doesn’t require large space.

The largest tidal project in the world was installed in Sihwa Lake Tidal Power Station in South Korea, with a capacity of 254 MW.

Question 2: Is Gold Renewable or Nonrenewable?

Answer: Gold is nonrenewable. Some metal ores and earth minerals like gold, silver, iron ore, titanium are often referred to as nonrenewable resources since they are similarly formed from geological processes and takes millions of years to the formation.

Question 3: Why is Nonrenewable Energy Bad?

Answer: Nonrenewable resources like coal, petroleum, natural gas emit a toxic gas called carbon dioxide. When this gas absorbs into the atmosphere; this creates a negative impact on the environment. One of the biggest problems that occur is global warming, leading to the melting of glaciers and a sudden rise in temperature during summers, and a sudden drop in temperature during winters. That’s why nonrenewable energy is bad for the environment.

Question 4: What is the Law of Conservation of Energy?

Answer: The law of conservation of energy states that the energy of a system of bodies when interacting with each other in a closed system remains constant.

For example, the potential energy of the pendulum swinging back down converts into kinetic energy; however, the sum of these two energies remain constant.