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 =
    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\%