Energy

• Electrical Energy - Whenever a current flows
• Light Energy - from the sun or light bulbs
• Sound energy - from loudspeakers
• Kinetic/Movement Energy - possessed by anything moving
• Nuclear energy - Released from nuclear reactions
• Thermal/Heat Energy - flows from hot to cold objects
• Elastic Potential Energy - possessed by springs, elastic, rubber bands, etc
• Chemical Energy - Possessed by foods, fuels, batteries, etc.

Potential and Chemical are forms of stored energy

Energy can never be created or destroyed. It can only be transferred from one form to another.

Energy is only useful when it can be transformed from one form to another.

Efficiency - The ratio of useful energy output to total energy input.

Efficiency = Useful energy output / Total energy input

• Useful devices are only useful because they can convert energy from one form to another
• When it does this, some energy is lost or wasted.
• The less energy a machine wastes, the more efficient it is.

CONDUCTION - The process where vibrating particles pass on their extra kinetic energy to neighbouring particles.

It occurs mainly in SOLIDS

• in a solid, the particles are held tightly together.
• when one particle vibrates, it collides with other particles near it.
• so the heat energy passes to those particles
• this process continues thoughout the whole solid.

CONVECTION - It occurs when more energetic particles move from a hotter region to a cooler region, taking their heat energy along with them.

It occurs in LIQUIDS and GASES.

EXAMPLE : Immersion Heater

• Heat energy is transferred from heater coils to water by conduction.
• The particles near the coils get more energy, and start moving faster and faster.
• The water expands and becomes less dense.
• The water becomes hot, and rises above the cooler water. It displaces the cooler water, making it sink towards the heater coils.
• The cold water gets heated by the coils.

RADIATION - The transfer of heat by electromagnetic waves.

It occurs in SOLIDS, LIQUIDS and GASES.

• It consists of electromangetic waves of a certain range of frequencies.
• If an object is hotter than its surroundings, it will emit more radiation and absorb less.
• If an object is cooler than its surroundings, it will absorb more radiation and emit less.
• ALL objects are continually emitting and absorbing heat radiation.