Energy Stores and Transfer

Energy

Energy is the capacity of a physical system to perform work.

Energy Stores and Transfers

Energy can be divided into:

• Energy Stores

• Energy Transfers

Types of Energy Stores

• Kinetic energy: Energy possessed by an object due to its motion. $KE = <br>ewline \frac{1}{2}mv^2$, where $m$ is mass and $v$ is velocity.

• Gravitational Potential Energy (GPE): Energy stored in an object due to its position relative to a gravitational body. $PE = mgh$, where $m$ is mass, $g$ is gravity, and $h$ is height.

• Chemical energy: Energy stored in the bonds of chemical compounds.

• Nuclear energy: Energy stored in the nucleus of an atom, released during nuclear reactions.

• Strain/Elastic Energy: Energy stored in a stretched or compressed elastic object.

• Internal Energy: Sum of the kinetic and potential energies of particles within a system.

• Thermal energy: Energy associated with the temperature of an object or substance.

• Electrical Energy: Energy carried by an electric current or stored in an electric field.

Energy Transfers

Energy can be transferred:

1. By a Force: Lifting an object imparts gravitational potential energy; applying force to set something in motion imparts kinetic energy.

2. By Heating: Energy is transferred from a hot object to its cooler surroundings.

3. By Radiation: Energy is transferred via light, infrared, and ultraviolet radiation.

4. By Electric Current: Electric current transfers energy between locations.

Conservation of Energy

Energy cannot be created or destroyed; it can only be transformed, transferred, or stored. The principle of conservation of energy states that the total energy in an isolated system remains constant.

Calculating Kinetic Energy

$K.E = \frac{1}{2} * m * v^2$ where m is mass and v is speed.

Calculating Gravitational Potential Energy

$G.P.E = m * g * h$ where m is mass, g is gravitational acceleration, and h is height.

Energy Efficiency

Efficiency is the fraction of energy supplied that is usefully transferred.

$Efficiency = \frac{useful \ energy \ output}{total \ energy \ output}$

$Percentage \ Efficiency = \frac{useful \ energy \ output}{total \ energy \ output} * 100\%$