Physics

revision cards for core physics gcse

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Physics- Heat Transfers

Thermal Radiation- All objects emit thermal radiation- The hotter an object is, the more thermal radiation it emits.

Dark matt surfaces emit snd absorb more thermal radiation than light, shiny surfaces.

Conduction- Conduction in a metal is due to free electrons- non metals are poor conductors of metals because they do not have free electrons- good insulators have pockets of trapped air.

Covection-Convection happens when a fluid is heated- the heat makes htem less dense and they rise, ie, hot air rises

Heat loss from buildings can be reduced by cavity wall insulation, double glazing, loft insulation

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Using Energy

Forms of energy- Chemical, kinetic, gravitational potential, elastic,elcetrical, sound, light, thermal.....

Energy can chamge from one form to another- energy cannot be created or destroyed.

Useful energy- Energy transferred to where it is wanted in the form it is wanted, eg- rollercoaster- kinetic energy

Wasted energy- Energy that is not useful- eg- rollercoaster- sound and thermal (from friction)

Efficiency= useful energy transferred by a device / total energy transferred by a device- Wasted energy causes inefficiency!

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Electrical Energy

Electrical Energy- Eletrical energy is energy transfer due to an electrical current.

The more powerful a device is, the faster the rate at which it transforms energy.- The unit of power is watts.

The National Grid- is a network of cables and transformers

- We use step up transformers to increase the voltage to the grid voltage  - We use step down transformers to decrease the voltage for use in homes

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Generating Electricity

Wind power- turbines are driven by wind which turns a generator- pro- renewable- con- unsightly , unreliable

Hydro electric power- a wave generator is a floating generator turned by waves- pro-renewable, reliable- con- expensive

Solar Power- uses the sun to make power- pro- renewable- con- does not work at night

geothermal- comes from the energy released by radioactive substances deep inside the earth- pro-renewable, no pollution- con-expensive, only certain places have geothermal capabilities

Fossil fuels and nucleasr fuels are non renewable.

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