# P1

P1 AQA (Core Science)

INCLUDES:

Heat Transfer, Energy Transfer, Electrical Devices, Electrical Sources, Electromagnetic Radiation, Nuclear Radiation, Origins of the Universe

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## Heat Transfer (P1a - 1)

• to evaluate ways in which heat is transferred in and out of bodies and ways in which the rates of these transfers can be reduced

Conduction is heat flow through solids - can be stopped by trapping a layer of air around the body (involves particles)

Convection is heat flow through liquids & gases (involves particles)

All objects emit & absorb radiation

Thermal (infra-red) radiation is the transfer of energy by electromagnetic waves - all bodies emit & absorb it - the hotter a body is, the more energy is emmitted

Dark, matt surfaces are good absorbers & emitters of radiation - therefore, the lighter & more shiny a surface the worse it is at absorbing & emitting radiation

Shape and dimensions of a body affect the rate of heat transfer

(Bigger) temperature difference between an object and it's surroundings affect the rate of heat transfer

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## Energy Transfer (P1a - 2)

• to describe the intended energy transfers/transformations and the main energy wastages that occur with a range of devices
• to evaluate the effectiveness and cost effectiveness of methods to reduce heat loss

Efficiency = useful energy transferred by device                                                                              total energy supplied to device

Energy can't be created or destroyed <-- conservation of energy

Wasted and useful energy both eventually spread out to their surroundings - which become warmer <-- the further it spreads, the harder it becomes to use again

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## Electrical Devices (P1a - 3)

• to compare and contrast the particular advantages and disadvantages of using different using different electrical devices

Energy transferred = power x time <-- kWh = kW x h

Total cost = number of kWh x cost per kWh

The amount of electrical energy a device transforms depends on how long the appliance is switched on for and the rate at which the device transforms energy

Energy is measured in joules

In the National Grid --> increasing voltage reduces current so reduces energy loss through friction, thereby increasing efficiency

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## Electrical Sources (P1a - 4)

• to compare and contrast the particular advantages and disadvantages of different sources to generate electricity

Energy from renewable sources can drive turbines directly

Using different energy resources has a different effect on the environment <-- this includes the release of substances into the atmosphere, noise & visual pollution & the destruction of habitats

Advantages & disadvantages of different energy sources depend on the cost of building power stations, start up time of power stations, reliability of energy source, the relative cost of the energy generated and the location in which the energy is needed

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## Electromagnetic Radiation (P1b - 5) [1]

• to evaluate the possible hazards that come with types of electromagnetic radiation

Outside the body, gamma rays are most harmful and can penetrate the skin and get to internal organs <-- although they tend to pass through cells themselves, therefore causing little harm to the cells

Alpha and beta radiation is highly ionising

• to evaluate methods to reduce exposure to different types of electromagnetic radiation

When people are around sources of radiation, full protective suits are often worn - many are often lead-lined to stop gamma rays getting through as gamma rays can kill cells

The electromagnetic spectrum is continuous but can be grouped into types of increasing wavelength & decreasing frequency

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## Electromagnetic Radiation (P1b - 5) [2]

The spectrum -->

Gamma, X ray, Ultraviolet, Visible Light, Infra-red, Microwaves, Radio-waves                     ||||||||||||| | | | | | | | |  |  |  |  |  |  |   |   |   |   |   |   |    |    |    |     |     |     |    |      |     |      |

When radiation is absorbed, the energy it carries makes the substance, which absorbs it, hotter and may create an alternating current with the same frequency as the radiation itself

Different wavelengths of electromagnetic radiation have different effects on living cells. Some radiation mostly pass through soft tissue without being absorbed, some produce heat, some may cause cancerous and some may kill cells (effects depend on the type & dose of radiation)

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## Electromagnetic Radiation (P1b - 5) [3]

Radio-waves, microwaves, infra-red and visible light can be used for communication

Microwaves can pass through the Earth's atmosphere and are used to send information to satellites

Communication signals may analogue (continuously varying) or digital (discrete values only). Digital signals are less prone to interference

Electromagnetic waves obey the wave formula -->

wave speed = frequency x wavelength <-- m/s = Hz x m

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## Nuclear Radiation (P1b - 6)

• to evaluate the possible hazards associated with the use of the different types of nuclear radiation

(Radiation) (Use) (Hazard) (Stopped by...) (Deflected by...)

(Alpha) (Used in smoke detectors) (If taken into the body (ingested) alpha emitters harm tissue) (Stopped  by paper) (Electric and magnetic fields)

(Beta) (Checking thickness of paper sheets in manufacture and radioactive tracers) (Some risk of tissue damage -->not as bad as alpha) (Stopped by aluminium) (Electric and magnetic fields)

(Gamma) (Medical research and non-destructive casting tests) (Can cause genetic damage and cancer) (Stopped by lead) (Nothing)

Some substances give out radiation from the nuclei of their atoms all of the time, whatever is done to them <-- they are radioactive

Half-life is the time it takes for the count rate to halve or the time it takes for the number of nuclei to halve

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## Origins of the Universe (P1b - 7)

• to compare and contrast the particular advantages and disadvantages of using different types of telescope on Earth and in space to make observations on and deductions about the Universe

If a wave source is moving relative to an observer there will be a change in the observed wavelength and frequency

There is a red-shift in light observed from the most distant galaxies

How the observed red-shift provides evidence that the Universe is expanding and supports the 'Big Bang' theory

The 'Big Bang' states that the Universe began from a very small initial point

Observations are made with telescopes that may detect visible light or other electromagnetic waves

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