Electrical Energy and Power

Electrical energy is the energy that comes from electric potential and electric current. It is a form of kinetic energy as it involves moving electrons.
In any electrical device or system, electrical energy is converted into other forms of energy such as heat, light, or mechanical energy.
Joule (J) is the SI unit for energy.

Power refers to the rate at which energy is transferred or transformed.
In electricity, power is the rate at which electrical energy is transferred by an electric circuit.
Power is calculated using the formula: P = IV where P is power, I is current, and V is voltage.
Power can also be calculated using another formula: P = I^2R where R is resistance. This formula is derived from the combination of Ohm’s law and the first power formula.
The SI unit for power is the Watt (W). One watt is defined as one joule per second.

Electrical energy can be transferred and converted into different forms of energy in electrical appliances.
For instance, in a light bulb, electrical energy is converted into light and heat energy.
Similarly, in an electric motor, electrical energy is converted into mechanical energy, which can then be used to do work.
The efficiency of an electrical appliance can be calculated using the formula: Efficiency = (useful power output / total power input) * 100%

The Law of Conservation of Energy states that energy cannot be created nor destroyed. It only changes from one form to another without any net loss or gain.
In any closed electrical system, the total energy remains constant. It just changes from electrical energy into other forms of energy like heat or light energy.
Understanding this energy conversion and transfer helps in assessing and improving the efficiency of electrical systems and devices.

The cost of electrical energy consumed by an appliance can be calculated by multiplying the energy used (in kilowatt-hours) by the cost per unit of electricity.
One kilowatt-hour (kWh), also known as a unit of energy, is the energy used by a 1kW appliance running for one hour.
If we know the power rating of an appliance and how long it is used, we can calculate the energy consumed using the formula: Energy = Power x Time.
It is essential to understand how to calculate the energy cost for reducing energy consumption and for making informed choices about using electrical appliances.