conservation and dissipation of energy



What is the Law of Conservation of Energy?

Energy cannot be created or destroyed, it can only be moved from one store to another.

- this means that the total amount of energy in a closed system remains constant, but the store and details regarding the store can change.

- energy cannot be 'lost' but transferred to waste energy.

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What are the energy changes in a TV?

electrical energy -> light energy + sound energy + thermal energy

- here, light and sound energy are useful transfers whereas thermal energy (from heating of wires) is wasted.

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What are the energy transfers in an electrical heater?

electrical energy -> thermal energy + sound energy + light energy

- in a gas cooker, the energy transfer is similar apart from the initial source.

chemical energy -> thermal energy + sound energy + light energy

- in both of these examples, thermal energy is the only useful transfer.

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- A rollercoaster increases its speed as it travels down a steep section and gains kinetic energy.

- When it travels up a steep section, this kinetic energy is transferred to gravitational potential.

- This energy transfer happens multiple times because the track is not consistent.

GPE -> KE -> GPE -> KE

- When the track is flat, the rollercoaster only has kinetic energy.

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What energy transfers occur when bouncing on a trampoline?

elastic potential energy -> kinetic energy -> gravitational potential

- some energy is transferred to the surroundings as well as sound and heat energy.

- when energy is transferred to the surroundings, we say it DISSIPATES

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