• Chemical energy: Energy is released when chemical reactions take place.
• Kinetic energy: The energy of a moving object
• Gravitational and Potential energy: Energy of an object due to it's position.
• Elastic/Strain energy: Energy stored in a springy object when we stretch and squash it.
• Electrical energy: Energy transferred by an electrical current.
• Thermal energy: Energy of an object due to its temperature.

Conservation of energy says that energy cannot be created or destroyed.

Chemical energy in Battery > Electrical energy > Light energy + Thermal energy

Gravitational potential energy > Kinetic energy (+ Sound) + thermal energy

The ability to do work. It is measure in Joules (J)

Useful energy is energy transferred to where it is wanted in the form it is wanted.

Wasted energy is the energy that is not usefully transferred or transformed.

E.G. Using a drill, particularly a blunt one, creates lots of heat. However, we only want to create a hole so the heat is wasted energy.

It is transferred to the surroundings. The energy become less useful the more it spreads out.

Power = Work or energy/ Time

Because of a small amount of wasted energy on sound and air resistance. 

Efficiency = (Useful energy transferred by the device) / (Total energy supplied to the device)

You can write the answer as a decimal or x 100 to get the percentage efficiency.

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A Sankey Diagram.