GCSE Physics Revision: Energy notes

Energy

Energy is the ability to do work or cause a change. It can be stored and transferred between different objects or systems. There are different types of energy, including kinetic energy, gravitational potential energy, and thermal energy.

Energy Stores and Transfers

Energy can be stored in different ways, including:

  • Kinetic energy - the energy of moving objects
  • Gravitational potential energy - the energy an object has due to its position above the ground
  • Elastic potential energy - the energy stored in an object that is stretched or compressed
  • Chemical energy - the energy stored in the bonds between atoms and molecules
  • Nuclear energy - the energy stored in the nucleus of an atom
  • Thermal energy - the energy associated with the temperature of an object or system
  • Electrical energy - the energy associated with the movement of electric charge
  • Light energy - the energy associated with electromagnetic radiation

Energy can also be transferred between objects or systems in different ways, including:

  • Mechanical work - the transfer of energy through a force acting over a distance
  • Heat transfer - the transfer of thermal energy from a hotter object to a cooler object
  • Electrical work - the transfer of energy through electrical circuits
  • Light energy transfer - the transfer of energy through electromagnetic radiation

Kinetic Energy

Kinetic energy is the energy of moving objects. It depends on the mass and velocity of the object, and is given by the equation:

Kinetic energy (J) = 1/2 × Mass (kg) × Velocity^2 (m/s)^2

Gravitational Potential Energy

Gravitational potential energy is the energy an object has due to its position above the ground. It depends on the height of the object and the strength of the gravitational field, and is given by the equation:

Gravitational potential energy (J) = Mass (kg) × Gravitational field strength (N/kg) × Height (m)

Work and Power

Work is the transfer of energy through a force acting over a distance. It is given by the equation:

Work (J) = Force (N) × Distance (m)

Power is the rate at which work is done, and is given by the equation:

Power (W) = Work (J) ÷ Time (s)

Heat Transfer

Heat can be transferred between objects or systems in different ways:

  • Conduction - the transfer of thermal energy through a material without any net movement of the material as a whole
  • Convection - the transfer of thermal energy through the movement of fluids (such as air or water)
  • Radiation - the transfer of thermal energy through electromagnetic radiation (such as light or infrared radiation)

Efficiency

The efficiency of a system is a measure of how much useful energy output is produced for a given amount of energy input. It can be calculated using the equation:

Efficiency = Useful energy output ÷ Total energy input × 100%

Efficiency is always less than 100%, as some energy is always lost to the surroundings as waste heat.

Energy Generation

There are different ways to generate energy, including:

  • Solar energy - energy generated from the sun through solar panels or solar cells
  • Fossil fuels - energy generated from burning oil, coal, or gas
  • Nuclear energy - energy generated from nuclear reactions in power plants
  • Renewable energy - energy generated from sources that can be replenished, such as wind, water, or geothermal energy

The choice of energy generation method can have environmental and economic impacts.

Key Equations

  • Kinetic energy (J) = 1/2 × Mass (kg) × Velocity^2 (m/s)^2
  • Gravitational potential energy (J) = Mass (kg) × Gravitational field strength (N/kg) × Height (m)
  • Work (J) = Force (N) × Distance (m)
  • Power (W) = Work (J) ÷ Time (s)
  • Efficiency = Useful energy output ÷ Total energy input × 100%