Energy

• When energy is transferred to an object, the energy is stored in one of the object's energy stores
• The 8 energy stores are: Thermal, kinetic, gravitational potential, elastic potential, chemical, magnetic, electrostatic and nuclear energy
• Energy is transferred mechanically, electrically, by heating or by radiation
• When a system changes, energy is transferred. It can be transferred into or away from the system, between different objects in the system or between different types of energy stores
• Closed systems are systems where neither matter nor energy can enter or leave. The net change in the total energy of a closed system is always zero
• Work done is another word for energy transferred
• Thermal energy refers to the energy contained within the system that is responsible for its temperature
• Kinetic energy is the energy found in any object which is moving
• Gravitational Potential energy is when an object has been raised above ground level
• Elastic Potential energy is stored in any object which can be stretched, compressed or squashed
• Chemical Energy is usually found in foods, fuels or batteries and is stored in the bonds of chemical compounds
• Magnetic energy is the energy stored in a magnet's magnetic field.
• Electrostatic energy is the energy stored in the electrostatic forces between two charged objects.
• Nuclear energy is the energy released when an atom splits into smaller atoms.
• Movement means energy in an object's kinetic energy store
• Ek = 1/2mv^2
• Kinetic energy = 1/2 x mass x speed squared
• Raised objects store energy in the gravitational potential energy stores
• Ep = mgh
• Gravitational Potential energy = mass x gravitational field strength x height
• The gravitational field strength of Earth is 9.8 N/kg
• Energy lost from the gravitational potential energy store = energy gained in the kinetic energy store
• Stretching can transfer energy to elastic potential energy stores
• Ee = 1/2ke^2
• Elastic Potential Energy = 1/2 x spring constant x extension squared
• Specific heat capacity is the amount of energy required needed to raise 1kg of a substance by 1 degrees Celsius
• Change in thermal energy = mass x specific heat capacity x temperature change
• Delta E = m x c x delta temperature
• The conservation of energy states that energy cannot be created or destroyed, only transferred from one store to another or dissipated
• Dissipated energy is energy which is wasted
• Power is the rate of doing work per second
• Power is measured in watts
• Energy is measured in Joules
• P = E/t
• Conduction occurs mainly in solids
• Conduction is the process where vibrating particles transfer energy to neighbouring particles
• Thermal conductivity is a measure of how quickly energy is transferred through a material. Materials with a high thermal conductivity transfer energy between their particles quickly
• Metals are good conductors because they have free electrons that can move around easily, allowing them to carry heat energy away from hotter parts of an object.
• Insulators are bad conductors as there are no free electrons so it takes longer for energy to be transferred between particles
• Convection only occurs in liquids and gases