What is energy in physics? Unit, Types of energy.

Definition of energy

What is energy in physics: The simple answer to this question is the ability or capacity to perform work. But in Physics energy is a property of an object which can be transferred to other objects or converted into different forms. It is not possible to give a general description of energy because of its different forms.

We are live in a world having energy everywhere. Energy is inside as well as outside the body. For instance, Air, water, soil, fire, and sun are various sources of energy. The source which are extensively used are conventional source. Which are not used excessively are non-conventional sources of energy.

Conventional sources fulfill the major part of the demand of energy. Non conventional are alternate sources of energy. Hydro energy, biomass, natural gas, and fossil fuels are conventional sources whereas solar energy, tidal power, and nuclear power, wave energy and geothermal energy are some of the non-conventional sources of energy.

Unit of energy

For the Quantitative discussion we need units to measure the energy. The energy of a body is define as its capacity for doing work. The unit of energy is same as that of work i.e. “Joule” In SI system and “erg”  in the CGS system. joule symbolic representation is J.

Energy (J)  =  Force(N) *Distance(M)

1 joule is define as the energy supply by the force of 1 Newton to move an object through a distance of 1 metre. Joule is dimensionally equivalent to 1 Newton metre. 

Sometimes energy is measure in terms of power.  Practically energy and power are different but power consumed energy. So If the power of an electric heater is 1 kilowatt and it works for an hour,  it consumes one kilowatt-hour (kWh) of energy.

In discussion of energy production and consumption, the Unit barrel of oil  equivalent and ton of oil equivalent are often use. The imperial/US units for Energy foot – pound force (1.3558J), the British thermal unit (btu).  Which has various value in the region of 1055J, the horsepower-hour(2.6845 MJ), and the gasoline gallon equivalent (about 120 MJ).

Basic form of energy in physics

1. Kinetic energy :

The energy possessed by any  moving object is kinetic energy. When we are moving or doing some work, the energy of our body (viz thermal energy) is converted into kinetic energy. For example flowing river, moving air and water stream/fall possess kinetic energy. Mathematically kinetic energy equal to the product of half the mass (m) of the object and the square of its velocity (v).

                                      Kinetic energy = 1/2 m v²

Where energy is in joule(J) mass in Kilogram (Kg) and velocity in metre per second(m/s).

2. Potential Energy :

Potential energy is the energy due of height, shape and configuration that is the quartz and Spring of watch (due to the configuration) and water store in the reservoir (due to height). The water has the potential to fall, and therefore contain a certain amount of energy. more potential energy is available when there is more water and is at a higher height. Potential energy is expressed as a product of mass(m), acceleration due to gravity (g) and height (h).

                               P.E.= mgh

whereas the configuration is involve the potential energy can be express as :

                               P.E.= ½ kx².

Where x is the displacement and k is the force constant.

3. Radiation Energy :

The radiation is a packet of energy or quanta of energy. Energy stored in rays is called radiation energy. That is to the best example of radiation energy is solar energy. Also the radiation coming from a light or a fire can be use for various purposes like eating, cooking and lightning.

Radiation energy (E) = Planks constant (h) * frequency of radiation (v)

4. Chemical energy :

Energy we get from organic and inorganic fuels is called chemical energy. Wood and oil contain energy in a chemical form. In batteries or Cell chemical energy is convert into electrical energy and vice versa. Medicines are also the source of chemical energy which help our body to fight against diseases and make us physically fit.

Classification of energy sources in physics

1. Renewable sources: Energy sources that can be renewed again and again are known as Renewable Sources. They are available in very large amounts as a result probably they will never execute. For example Sun, Biomass, water, wind, wood etc.
2. Non-renewable sources: Energy sources that cannot be used again and again are renewable sources of energy. In short they are available in Limited quantity and they will execute one day. These are the conventional source which are decreasing with the time and cannot be replenished or renewed for further use. These sources are called exhaustible resources. Mineral sources are like fossil fuels, nuclear fuels and non – renewable sources

Human body have different types of energy –

On the basis of physics, thermal energy helps us to maintain constant body temperature. Mechanical energy helps us to move, electrical energy sends nerve impulses and fires signals to and from our brains.

Frequently Asked Question on Energy in Physics