types of energy and energy transfers:

What is Energy?

Energy is the ability to cause change or do work. The standard unit of energy is the joule (J).

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Law of Conservation of Energy

Energy cannot be created or destroyed – it can only be transferred or transformed.

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Main Energy Stores:

• Kinetic Energy – A moving bicycle
• Thermal Energy – Heat from a burning candle
• Chemical Energy – Energy stored in a battery
• Electrical Energy – Current flowing through a wire
• Light Energy – Light emitted from a light bulb
• Nuclear Energy – Energy released from a nuclear reactor
• Gravitational Potential Energy – A rock at the edge of a cliff
• Elastic Potential Energy – A stretched trampoline surface
• Sound Energy – Sound produced by a ringing bell

Energy Transfer Pathways:

• Mechanically – A hammer hitting a nail
• Electrically – A toaster heating bread using an electric current
• Heating – A metal rod warming up when placed in a flame
• Radiation – The Sun warming your skin through infrared rays

Systems:

• Open System – energy and matter can be transferred to surroundings
• Closed System – energy stays within the system, no matter transfer to surroundings

Useful vs Wasted Energy:

• Useful energy: energy that is transferred into the desired form
• Wasted energy: energy that is not usefully transferred (e.g. heat or sound)

Examples of Energy Transfers:

• A light bulb transforms electrical energy → light + heat (wasted)
• A motor transforms electrical energy → kinetic + sound (wasted)

energy transformations and conservation:

Energy is transformed from one form to another.

Example: A rollercoaster at the top has gravitational potential energy, which becomes kinetic energy as it descends.

In every energy transformation, some energy is wasted (usually as heat or sound).

Ways to reduce energy loss:

• Lubrication (reduces friction)
• Insulation (reduces heat loss)