Transfer of Energy

Definitions and Basic Concepts

Energy is the ability to do work or cause change. It can take on various forms, such as kinetic energy, potential energy, thermal energy, chemical energy, and electrical energy.
The Law of Conservation of Energy states that energy cannot be created or destroyed, only transferred or converted from one form to another.
Electrical energy is energy derived from electric potential energy or kinetic energy. It is used to power electrical devices such as lights, heaters, and electronic devices.
Thermal energy is the internal energy of an object due to the kinetic energy of its atoms or molecules. It’s usually associated with heat.
Practical electrical appliances are devices that convert electrical energy into other useful forms of energy.

Every electrical appliance is designed to transfer electrical energy into other forms of energy efficiently.
A light bulb converts electrical energy into light energy and some unwanted thermal energy.
An electric heater converts electrical energy into mainly thermal energy.
A loudspeaker converts electrical energy into sound energy and some wasted thermal energy.
In every energy transfer, some energy is ‘wasted’ or dissipated as thermal energy. This is due to the resistance in the circuits and components of the appliance.
This ‘wasted’ energy is actually energy that has been transformed into a less useful form, usually thermal energy. This is dissipated into the surroundings, warming them very slightly.

Energy efficiency is a measure of how well a device converts energy input into useful output. This is usually expressed as a percentage.
The formula for calculating energy efficiency is efficiency = (useful energy output / total energy input) x 100%.
Improving energy efficiency in appliances and systems leads to energy conservation, saving money, and reducing environmental impact.
Devices are often rated in terms of energy use per unit of time, known as power. The unit of power is the watt (W).

It is important to understand the difference between energy transfer and energy transformation. Energy transfer refers to the movement of energy from one place to another. Energy transformation, on the other hand, refers to the change of energy from one form to another, as in a light bulb or a heater.
The total energy input of an electric appliance equals the electrical power (in watts) multiplied by the time the appliance is used.
All energy ‘wasted’ in an electrical device is usually transformed into heat due to resistance in the electrical circuits and components.
Even though energy is always conserved and never ‘used up’, it can become less useful through the process of energy transformations and transfers.