# gateway physics p1 2012 foundation

suitable for entry level students

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• Created by: J lockley
• Created on: 13-11-12 16:12

## HEATING HOUSES

TEMPERATURE is a measure of how HOTsomething is

The unit of measurement is DEGREES CELSIUS

THERMOGRAMS represent temperature by a range of colours the hottest parts appear WHITE/YELLOW/RED;coldest areas appear BLACK/DARK BLUE/PURPLE

HEAT is a measurement of ENERGY and is measured in JOULES(J)

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## TEMPERATURE CHANGE

If there is a difference in temperature between an object and its surroundings, then HEAT ENERGY FLOWS from the HOTTER region to the COOLER region

Temperature RISE means the object is TAKING IN heat energy.

Temperature FALLING  means the object is GIVING OUT heat energy

An object that has a very HIGH temperature will cool down very quickly to start then as it's temperature drops it will cool down at a slower rate.

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## MEASURING HEAT ENERGY

The amount of ENERGY needed to raise the temperature of an object depends on:

• The MASS of the object
• The CHANGE in TEMPERATURE required
• The MATERIAL it is made from

To calculate the amount of energy used to bring about the change in temperature of an object you can use the following formula

total energy     =     energy supplied          x              number of

supplied                  per second                                  seconds.

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## SPECIFIC HEAT CAPACITY

Each MATERIAL has a VALUE of how much energy it can hold.

This is known as SPECIFIC HEAT CAPACITY.

It is the energy needed to raise the temperature of an object which weighs 1 kg by 1 degree Celsius.

The following equation is used to find the amount of energy required to raise the temperature of an object by a certain amount.

ENERGY= MASS x  SPECIFIC HEAT  x  TEMPERATURE

(J)        (kg)      CAPACITY (J/kg °C)     CHANGE(°C)

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## MELTING AND BOILING 1

ENERGY is needed to MELT or BOIL substances

At the point of melting the TEMPERATURE DOESN'T CHANGE

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## MELTING AND BOILING 2

Water temperature will never rise above 100 degrees Celsius, no matter how long it is heated for. But the temperature of the GAS (steam) produced can rise.

SPECIFIC LATENT HEAT is the amount of ENERGY required to MELT or BOIL  1Kg of material.

this depends on the:

• Amount of MATERIAL
• The state (SOLID,LIQUID or GAS)

ENERGY REQUIRED can be found by using the following formula

ENERGY (j) = MASS (Kg)  x SPECIFIC LATENT HEAT (j/Kg)

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## CONDUCTORS AND INSULATORS

CONDUCTORS are materials which allow ENERGY to flow through QUICKLY

METALS are good conductors

INSULATORS allow ENERGY through but much SLOWER

AIR,PLASTIC and WOOD are good Insulators.

CURTAINS are GOOD INSULATORS as they trap a layer of air between them and the  window this helps reduce energy loss.

AIR is a good insulator as its particles are very far apart.

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## CONDUCTORS AND INSULATORS

CONDUCTORS are materials which allow ENERGY to flow through QUICKLY

METALS are good conductors

INSULATORS allow ENERGY through but much SLOWER

AIR,PLASTIC and WOOD are good Insulators.

CURTAINS are GOOD INSULATORS as they trap a layer of air between them and the  window this helps reduce enegy loss.

AIR is a good insulator as its particles are very far apart.

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## TRANSFER OF HEAT ENERGY

Heat energy moves around.

HOT AIR rises and is REPLACED by COLDER AIR.

Heat energy can be transferred from one place to another by;

CONDUCTION - transfer of heat energy through a SOLID (e.g. Metals )

CONVECTIONtransfer of heat energy from hotter regions to cooler regions by the MOVEMENT OF PARTICLES  (e.g. liquids and gases like water and air )

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## PAYBACK TIME

PAYBACK TIME is how long (IN YEARS)  it takes to pay for the insulation you use in the home by all the savings you make.The formula is:

PAYBACK TIME (YEARS)  =          COST OF INSTALLING

ANNUAL SAVING

Method of insulation  cost        Annual saving   Payback time

Roof insulation        £400         £80              5 years

Double glazing         £1800       £60             30 years

Draught excluders     £40          £20              2 years

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## ENERGY EFFICIENCY

ENERGY EFFICIENCY is a measure of how good an appliance is at CONVERTING input energy into USEFUL output energy.

you can use this calculation to work out efficiency

Efficiency = useful output energy (j)  x 100

total input energy (j)

Example:

A 60 watt light bulb USES 60 Joules of energy every second

and each second it GIVES OUT 6 joules of light energy.

efficiency = 6j x 100        =       0.1 x 100 =     10 %

60j

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## Transfer of heat energy

• AIR is a GOOD INSULATOR this is because the particles are far apart.
• If AIR is TRAPPED in a material ,the material will be a good insulator
• Heat energy moves from one place to another

CONDUCTION is the transfer of heat energy THROUGH A SUBSTANCE from a HOTTER region to a COOLER region.        (Occurs in solid objects like metal rods)

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## Transfer of heat (2)

CONVECTION is the transfer of heat energy from hotter regions to cooler regions by THE MOVEMENT OF PARTICLES.

(Occurs in liquids and air, hot air rises as it becomes less dense(lighter) and is replaced by cold air, then as the hot air  cools and becomes more dense it sinks. This creates a convection current.)

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## Transfer of heat energy (3)

hot objects emit mainly infra-red radiation, an electromagnetic wave. The amount of radiation given out depends on the objects surface.

DARK MATT surfaces emit more than light,shiny surfaces

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## Spectrum of waves

Light is a transverse wave.

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## Light

LIGHT is a transverse wave and it has the following features.

• AMPLITUDE - maximum disturbance caused by the wave.
• WAVELENGTH - the distance between one crest to the next
• FREQUENCY - the number of waves produced in one second

The electromagnetic spectrum order.

Real Men Ignore Violence Using x-box Games.

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# Wave speed

How fast do waves travel?

The speed of a wave - its wave speed - is related to its frequency and wavelength, according to this equation:

wave speed (m/s) = frequency (hertz, Hz) × wavelength (metre, m)

For example, a wave with a frequency of 100 Hz and a wavelength of 2m travels at 100 × 2 = 200 m/s.

a tuning fork with a frequency of 480Hz produces sound waves of wavelength 70cm.

What is the speed?

(To convert cm to m divide by 100 before doing equation)

So wave speed = 480Hz x 0.7m = 336 m/s

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## Reflection and refraction

Light can be reflected from multiple surfaces

An optical fibre is a thin rod of high-quality glass. Very little light is absorbed by the glass. Light getting in at one end undergoes repeated total internal reflection, even when the fibre is bent, and emerges at the other end.

Information such as computer data and telephone calls can be converted into electrical signals. These can be carried through cables, or transmitted as microwaves or radio waves.The information can also be converted into either visible light signals or infrared signals, and transmitted by optical fibres.

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## morse codes

Morse code is a digital signal. It can be transmitted in many different ways, including visible light, radio waves and electrical pulses.

Sending information using electrical pulses requires wires, unlike visible light and radio waves, which are wireless. The use of visible light needs the transmitter and receiver to be in the line of sight, but that is more secure against eavesdroppers than radio waves.

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# Total internal reflection

Light rays and infrared rays change speed when they pass from glass to air, or Perspex to air. This is because air and glass - or Perspex - have different densities. The rays change direction if they hit the boundary of the material at an angle other than 90°. Beyond a certain angle, called the critical angle, all the rays reflect back into the glass or Perspex. This is called total internal reflection, TIR.

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## diffraction

As waves pass through a gap or opening ( such as a door), the edges SPREAD out.

This is called DIFFRACTION.

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## cooking and communicating with waves

The amount of radiation which is absorbed or emitted given out)depends on

• surface temperature
• colour       -      black is good, white and silver are poor.
• texture     -       dull is good, shiny is poor

MICROWAVES

USES:

heat up food, communication from satellites, mobile phones, radar.

THEY:

absorbed by water and fat molecules

penetrate 1cm into food

travel through glass and plastic

are reflected by shiny surfaces

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## Microwaves

Microwaves are used to TRANSMIT information over large distances, these need to be in LINE OF SIGHT,if not you have a poor signal. This is why you sometimes lose your mobile phone signal. Trees or mountains can block the signal, as can poor weather, the curvature of the Earth and interference between other signals.

These effects can be reduced by putting the transmitters closer to each other or placing masts up high, like tops of buildings or mountains.

The microwave signals are a different wavelengths to the ones used to cook food in microwave ovens.

Can microwaves emitted from mobile phones harm you?

• for example may cause brain or ear tumours or changes to your DNA.
• Children are more at risk as skulls are thin.
• risk is increased if used a lot.
• people are also concerned about the big masts and dangers associated if you live close to them

Scientists publish stuidies so other scientists can read it and share their work.

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## data transmission

Infrared signals

This is a type of electromgnetic wave.

Uses of infrared:

• remote controls for T.V, SKY etc.
• sensors for doors
• short wifi links for computers
• burglar alarms and security lights (by detecting body heat)

Infrared signals are DIGITAL codes.

When a button is pressed the code is transmitted to the device by a series of flashes

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## data transmission

ANALOGUE AND DIGITAL SIGNALS

ANALOGUE

These signals can be used to transmit data .

They vary continously in AMPLITUDE.

Analogue signals suffer from INTERFERENCE in the form of noise.

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## data transmission 2

DIGITAL SIGNALS

digital

These signals can be used to transmit data .

They do not vary but are a series of pulses

digital signals either on (1) or off (2)

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## data transmission 3

• more stations available
• less interference with broadcasts from other stations

• sound quality is not as good as FM broadcasts
• some areas can not receive DAB
• (the short waves are not good at diffracting around hills)
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## wireless signals

Radiation (RADIO WAVES)used for communication can be reflected by the atmosphere (ionosphere). This allows broadcasts to be received around the curve of the Earth.

WIRELESS technology (RADIO AND MICROWAVES) is used for TV and radio, mobile phones and laptops (internet).

ADVANTAGES: no connection needed to landline,portable, can be accessed on the move, no wires.

DISADVANTAGES: aerial needed to pick up signal

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## Stable Earth

Earthquakes produce shockwaves which travel inside the Earth.They can damage buildings and cause tsunamis.These waves are called SEISMIC WAVES

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## GLOBAL WARMING

Many scientists beleive that we are experiencing GLOBAL WARMING, which may have implications for the Earth in the future.

Three factors that contribute to GW are:

• increased ENERGY use in homes
• increased CARBON DIOXIDE (CO2) emmisions friom burning FOSSIL FUELS
• Deforestation (cutting down of trees, they take the CO2 out of the atmosphere and use it in Photosynthesis)
• Weather patterns also contribute:
• dust from volcanoes REFLECTS radiation from the sun back to space , causing COOLING
• dust from factories reflects radiation from cities back towards Earth causing WARMING
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## Dangerous sun

The sun produces electromagnetic waves.

Prolonged exposure can cause sun tan, sun burn, cateracts of the eyes, ageing of the skin and skin cancer.

SUNSCREEN can be effective at reducing the damage of UV rays. The higher the factor the lower the risk.

Sunscreen increases the time you can stay out in the sun.

In England the time recommended is 20 mins.

If you use 30 factor sunscreen it means 30 x 20 mins which  = 600 mins which is 10 hours so you are covered for 10 hours

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## dangerous sun 2

People who have DARKER skin tones have a reduced risk of developing skin cancer. skin cancer develops in the MELANIN of the skin.

DARK skin ABSORBS more UV radiation than PALE skin.

Therefore less radiation reaches the delicate body tissues underneath.

To reduce the risk of sunburn and skin cancer:

• stay out of the sun at midday
• keep skin covered
• avoid sunbeds
• always use sunblocks or sunscreen
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## ozone layer

OZONE is a gas found naturally high up in Earth's atmosphere

It prevents too many harmful UV rays reaching the EARTH

Scientists need to make sure the data they collect is accurate,to do this they must repeat there experiments, look at other scientists results, test their predictions.

The use of CFC's and fridge coolants has caused thinning of the OZONE layer,and Scientist have noticed a direct link to this thinning and the rise in skin cancer

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