Electrical Energy

Electrical energy is not a primary source of energy. It is a secondary source because it is produced from primary energy sources such as coal, natural gas, nuclear energy, solar energy, and wind energy. These primary sources drive electric generators and solar cells to produce electricity for easy use and transport.

Electrical cables transport electricity from one place to another through conduction. Conductors made from metal are used for this purpose. This method of transporting electrical energy for hundreds of miles is called an electrical grid. The electrical grid’s rate of energy transfer is called electrical power.

The quantity of electrical energy transferred to an appliance depends on its power and the duration it is switched on. The amount transferred from the mains is measured in kilowatt-hours or kWh. It is the commercial unit of electricity. One unit is 1 kWh.

Equation

The equation for electrical energy is given by the following:

E = P x t

Where

E : Energy transferred in kWh (1 kWh = 3.6 x 10⁶ J)

P : Power of the appliance in kW (1 kW = 1000 W)

t : Amount of time in hours that the appliance operates ( 1 h = 3600 s)

Example: If a 60-Watt lamp is turned on for two hours, how many joules of electrical energy are converted?

Given P = 60 W, and t = 2 h = 2 x 3600 = 7200 s

We have,

E = P x t

Or, E = 60 Js^-1 x 7200 s

Or, E = 432,000 J or 432 kJ

• In homes, the energy coming from power outlets is electrical energy. This energy is used to power devices like television, refrigerator, and electric heater.
• A chemical reaction produces positive charges and negatively charged electrons in a car battery. These charges are present in an electrolytic solution as ions. The chemical energy from the reaction drives the electrons, which then flow through the circuit and produce electrical energy.
• During a thunderstorm, lightning is observed. Lightning is nothing but charged particles in motion. So, what we see is electrical energy in the atmosphere being discharged.
• Electric eels can generate electrical energy. They use it to guard against predators and to shock their prey.
• In biological systems, hydrogen ions, electrons, or metal ions may be more concentrated on one side of a membrane than the other. Therefore, setting up an electrical potential allows for transmitting nerve impulses and moving muscles.

The law of conservation of energy states that energy cannot be created or destroyed. It is converted from one form into another. Below are some examples in which other forms of energy are converted into electrical energy.

1. Nuclear Power Plant

In a nuclear power plant, nuclear energy is converted into electrical energy. A fission reaction generates heat that converts water into steam. The steam rotates turbine blades that drive a generator to make electricity.

2. Hydroelectric Plant

In a hydroelectric plant, water falling from a certain height rotates a set of turbines. The turbines power the generators that are connected to them and create electrical energy.

3. Geothermal Power Plant

In a geothermal power plant, water present in reservoirs beneath Earth’s surface produces steam through natural means. The steam rotates a turbine that activates a generator, producing electricity.

4. Wind Turbine

An example of a machine that converts mechanical into electrical energy is a wind turbine. The blowing wind turns the turbine blades. The mechanical motion of the blades fires up an electric generator, creating electrical energy.

5. Solar Cells

Solar energy is produced directly from the sun. The sun’s rays strike solar cells or photovoltaic cells and generate a small electric voltage. By connecting large numbers of individual cells, a large amount of electricity can be generated in a solar electric plant.

6. Piezoelectricity

Kinetic energy can be converted to electrical energy through piezoelectricity. When sound energy, a form of kinetic energy, is applied to a piezoelectric material, it creates strain in the crystal and produces an electric current. The current is then harvested into electricity.