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What is Electrical Energy? Its Unit, Formula & Applications

Electrical Energy, Its Unit, Formula and Applications

What is Energy?

Energy is the capacity for doing work or the ability to do some work is known as energy.

Energy exists in different forms (such as electrical, mechanical, heat, light etc.) and can be converted from one to another form. For example,

  • A lead acid cell converts chemical energy into electrical energy
  • A generator converts mechanical energy into electrical energy,
  • A motor converts electrical energy into mechanical energy
  • An electric radiator converts the electrical energy into heat energy
  • A light bulb converts the electrical energy into light energy

Keep in mind that a change in the energy is must for work done. The unit of heat, mechanical and electrical energy in the MKS system is Joules. The unit of Work and Electric Energy in S.I system in Joule (named after English physicist James Prescott Joule).

What is Electrical Energy Its Unit, Formula & Applications

What is Electrical Energy?

Electrical energy is a type of energy caused by the movement of charge or electrons. In other words, a form of energy derived and converted from kinetic energy or electrical potential energy.

Electrical energy is a type of kinetic energy because of the movement of charge from one point to another. When produced, all the electrical energy is the form of potential energy when delivered to the final application which can be converted to another form of energy i.e. from electrical to mechanical through electric motors and heat or motion through motors and light bulbs & heaters etc.

Electrical energy is generated (converted) from other forms of energies in electric power plant houses and stations. The generated energy (in the form of electricity) furtherly provided to the residential and commercial consumers through proper transmission and distribution systems.

Keep in mind that Electrical energy is a different quantity than the Electric power where power is the rate of doing work or power is the rate at which energy is used or power is the rate of converting energy.

Formula and Equation of Electrical Energy

The amount of work done by energy is equal to moving an amount of “Q” coulombs of charges by “V” volts of potential difference (or voltage).

Work done = Volts x Q coulombs

W = V x Q

Now, a current of “I” amperes flowing for time “t” second through a circuit having a resistance of “R” ohms, the work done is same as for the above statement i.e. work done or utilized electrical energy is equal to the VD x Q joules. Where VD is the voltage drop across the resistor in the circuit and the value of VD is equal to IR. i.e.

V = IR

But we know that I = Qt


Energy expended = VQ     …     (i)

Putting the value of Q = It in equation (i)

Energy expended = VIt     Joules     …     (ii)

Now, putting the value of V = IR in equation (ii)

Electrical Energy = IR x It = I2Rt     joules     …     (iii)

Now again, put the value of I = V/R (Ohm’s law) in equation (iii)

Work done = (V2/R2) x R t

Work done = (V2/R) x t     …     (iv)

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Unit of Electrical Energy

The unit of electrical energy is Joule or Watt – Second. It is a very basic and small unit, for this reason Wh (Watt-hour) or kWh (kilo-watt-hour is used for commercial application to measure the consumption of electrical energy through energy metering. Generally, electric power supplier and utilities measures the electrical energy (electricity utility bill) by installing electric energy meters at the user end.

If 1 volt (potential difference) is applied across a circuit and 1 ampere of current is flowing through it for 1 second, then the work done or amount of electrical energy would be 1 joule or watt-second.

1 J = 1 W x 1 s

A kilo-watt-hour (kWh) is also known as a board of trade (B.O.T) unit.

1 Board of Trade Unit = 1 B.O.T Unit = 1kWh = 1000Wh = 36 x105 = 3.6 MJ     …     Joule or Watt-seconds

Note that energy and work is much related to each other as energy is the ability to do some work while work is the result of changing energy from one form to another. In other words, the amount of expended energy is equal to the work done.

For this reason, both work and energy is represented by the symbol of “W”. Additionally, the S.I unit for both work and energy is same i.e. Joules represented by the symbol of “J”.

Sources and Types of Electrical Energy

Following are the basic sources of electric energy i.e. converting other energies into electrical energies.

  • Hydroelectric and Water head energy
  • Sun heat and light energy (for solar panels)
  • Wind power and energy
  • Nuclear Energy
  • Fossil Fuels, biofuels, biomass as nonrenewable energy (natural gas, coal, petroleum & oil etc. for boilers and steam turbines.)
  • Lightning as Transient energy

The following methods are used to obtained electrical energy by converting other forms of energies

  • Generators, alternators, windmills and hydroelectric power plants (converts mechanical energy into electrical energy).
  • Nuclear Power plant, geothermal and steam turbine power plant (converts thermal energy into electrical energy).
  • Batteries (converts chemicals energy into electrical energy).
  • Solar panel and arrays (converts the radiant energy into electrical energy).

The above sources of electrical energy can be converted into different types of electrical energy as follows.

  • AC (Alternating Current)
  • DC (Direct Current)

Additional forms of electrical energies are:

  • Static Electricity (Potential with no flow of electrons)
  • Dynamic Electricity (Potential with flow of electrons)
  • Electromagnetic & Electrostatic Energy

Applications of Electrical Energy

Electrical energy (i.e. electricity) is the backbone in our modern society and it is must for our day to day life and you can’t even imagine a life without electricity. There are vast amount of applications of electrical energy such as:

  • Electric motors, movers, generators and storage batteries etc. 
  • Transportation, vehicles, electric traction, plans and communication.
  • Escalators, elevators and electronic ladders.
  • Lighting, heating and cooling i.e. air conditioning, welding and molding etc.
  • Construction, manufacturing, healthcare, engineering, entertainment, electronics appliances, computers, machinery and much more.

In Short, you won’t be able to see useful things without electricity in household, office and commercial sites.

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