# Energy

## Energy

• Energy is a fundamental concept in physics, it is the capacity to do work or the ability to cause change.
• This can exist in numerous forms such as kinetic, potential, thermal, gravitational, sound, light, elastic, electromagnetic energy, etc.
• Energy has the unit of Joules (J) in the International System of Units (SI).
• It is a scalar quantity, having magnitude but not direction.
• In classical mechanics, energy is considered a conserved quantity that means the total energy of an isolated system cannot change—it is said to be conserved over time.
• Energy can be neither created nor destroyed but can only be changed from one form to another. This principle is known as the law of conservation of energy.

## Types of Energy

### Kinetic Energy

• It is the energy that an object possesses due to its motion.
• Mathematically, the kinetic energy (KE) of an object is given by the formula ½mv², where m is the mass of the object and v is its velocity.

### Potential Energy

• This is the energy stored in an object due to its position in a force field, or due to its configuration.
• There are several types of potential energy, including gravitational, elastic, chemical, nuclear, etc.
• The formula for gravitational potential energy is mgh, where m is the mass in kilograms, g is the acceleration due to gravity and h is the height above ground.

## Energy Conversion

• Energy conversion, also referred to as energy transformation, is any process of transforming energy from one form into another.
• For example, a light bulb transforms electrical energy into light and thermal energy.
• Energy conversion is subject to the law of conservation of energy.

## Energy Efficiency

• It refers to the amount of useful energy that can be extracted from a system.
• The efficiency of a device is the proportion of the energy input that is converted to useful energy and is usually expressed as a percentage.
• No real-world device is 100% efficient due to waste energy in practical applications, often in the form of heat due to friction.

Understanding these concepts about energy will prove valuable when you approach problems pertaining to work, energy, and power. Remember, practice and application of these ideas is the best way to prepare!