Physics 1A

My revision cards for Physics 1A

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  • Created by: Kivia
  • Created on: 23-02-12 20:31

Types of Energy

Energy is measured in joules, always remember to put it in capital leters as you dont get grade for lowercase

Types of Energy:

- Heat, Light, Sound, Chemical, Microwave, Radio Wave, kinetic and potential energy,

Solar radiation is responsible for the earth's weather systems and ocean currents


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Heat energy

Heat is a energy that can be transferred from one material to another. Temperature is a measure of the heat energy in a material.

Heat energy can be transferred by conduction, convection and thermal radiation.

Thermal radiation (infrared) is the transfer of heat energy by electromagnetic waves. All material ABSORB (take in) and EMIT (give out) thermal radiation.

The amount of thermal radiation an object emits is affected by...

It's shape. It's dimensions. The type of surface it has.

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Energy transfer and transformation

Energy transfer happens when the same form of energy transfers ( moves to) another, like the kinetic energy of a cyclist transfers to the bike. Energy transformation is when a form of energy transforms into another, such as electrical energy turning into light energy.

Free electrons in metal help to transfer energy rapidly between the fixed particles. (particles that vibrate more and get warmer as it absorbs more energy)

Thermal Conductors transfer heat energy easily, these are usually metals such as steel. Thermal Insulators do not, such as air and plastic.

In convection a gas or a liquid (fluids) moves carrying thermal energy with it. When heated, fluids expand, become less dense, and rise.

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Energy And Heat

Both wasted energy and the energy that is usefully transferred or transformed appears as heat energy,

Heat energy is transferred to the surroundings by conduction, convection and thermal radiation this means that the surroundings get warmer.

Energy gradually spreads out, and so is less and less useful for further energy transformations.

Energy is more useful when it is concentrated, as in fuels and batteries, this is called stores of energy.

(free electrons) Particles vibrate inside objects specially when absorbing any sort of energy as the particles vibrate more vigorously and it heats up. The more energy it absorbs the more the particles vibrates and the hotter it gets.

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How refrigerator works

It takes thermal energy to spread out amongst items of food, concentrates it and transfers it to the fins at he back of the refrigerator. A refrigerator transfers heat in the opposite direction to normal - from cold to warm air. It requires electrical energy to do this work

    Still don't know why I need this.

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Energy from the sun

The suns Energy comes from nuclear fusion, this is when the nuclei of atoms COMBINE. Two hydrogen nuclei FUSE to form helium nucleus and produce energy.

The mass of the helium is very slightly less than the mass of two hydrogen nuclei because mass had become energy.


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Energy types and Diagrams

Energy cannot be created or destroyed. It can only be transferred and transformed from one form to another. The total energy always remains constant. 

energy input = energy output = useful energy + wasted energy

A sankey diagram shows the energy input and output of a device. wasted energy is usually heat energy.

efficiency = useful energy output / total energy output

Work is measured in J (joules)  work done = force x distance travelled

Power is measured in W (watts) = work done / time

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Electrical current from the mains carries electrical energy which is transferred  to electrical appliances ( electrical equipment) 

Total amount of energy transferred (J) = power rating (W) x time (S)

the power rating of an appliance is the rate at which it transforms electrical energy.

The cost of energy that current transfers to an electrical appliance can be calculated:

- Number of kilowatt hours (kWh) used = power rating (W) x time (H)

- Cost of electricity = number of kilowatt hours used (kWh) x cost per kWh

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The national grid transmits electricity around the country at HIGH VOLTAGE and LOW CURRENT to reduce energy losses.

At substations, step-down transformers REDUCE VOLTAGE so that the electricity is at 230V wen it reaches consumers.

Power = current x voltage

the electrical energy from a current can be transformed into kinetic energy by a motor, which contains a wire coil rotating between magnets.

A dynamo produces electricity when coils of wire rotate inside a magnetic field

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In power stations fossil fuels and biomass are burned, or nuclear fuels react, to release energy as heat. The heat is used to produce steam which turns a turbine . The turbine then turn the generator producing electricity. 

Some power stations use hot, compressed gasses instead of steam.

Renewable energy sources include: wind, hydroelectric, tidal, wave and geothermal power.

All types of electricity generation have some harmful effects on people or the environment. There are also limitations on where they can be used.

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Electricity and the environment

Fossil fuel-burning produces gases that contribute to climate change but it is cheap and abundant.

waste-burning produces toxic gases may cause cancer and birth defects but it reduces need for landfill site.

Hydroelectric creates dams flood valley, destroys homes, farmland and wildlife habitat but it is cheap, clean and it is a renewable energy.

Tidal & Wave can change the water flow, disrupt shipping and destroy habitat but it has a very low running cost.

Geothermal might release dangerous gases from below the earth's surface but it has a low impact on the environment and is a small station.

wind turbine may  kill birds , is noisy and spoil landscape it is not 100% reliable but it is cheaper.

Nuclear creates radioactive pollution and generates nuclear waste but fuel is available and no greenhouse gases.

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