P1 - created from Mind Map

Seite 1

Heating Houses

Energy flow

Measuring temperature

Specific heat capacity

Specific latent heat

Energy flows from a warmer to a colder body. When energy flows away from a warm object, the temperature decreases

A thermogram uses colour to show temperature; hottest: white/yellow coldest:black/dark blue/purple.

Temperature is a measurement of hotness on a arbitary scale.

When the temperature of a body increases, the average kinetic energy of the particles increases

Heat is a measurement of internal energy, it is measured on an absolute scale.

Energy needed to raise the temperature of 1kg by 1 degree c

Measured in Joules per kg degree celsius j/kgoc

energy transferred = mass x specific heat capacity x temperature change

Energy needed to melt or boil 1kg of the material

Measured in Joules per kilogram J/kg

energy transferred = mass x specific latent heat

When a substance changes state, energy is need to break the bonds that hold the molecules together. This explains why there's no change in temperature.

Keeping homes warm

Practical insulation

Conduction, convection and radiation

Energy efficiency

Double Glazing - Reduces energy loss by conduction. Gap between 2 pieces if filled with gas/contains a vaccum. Particles in a gas are far apart, it's very difficult to transfer energy

Loft insulation - reduces energy loss by conduction and convection. - Warm air rises - Energy is transferred through ceiling by conduction - Air in loft is warmed and trapped by insulation, both sides are same temp so no energy is transferred

Cavity wall- reduces energy loss by conduction and convection. Air in foam is good insulator, and the air can't move because it's caught in the foam

Insulation blocks- used to build new homes, shiny foil on both sides to reduce radiation; - energy from sun is reflected to keep the home cool in summer, energy from home is reflected back to keep home warm in winter

Conduction - due to the transfer of kinetic energy between particles

Convection - Gas expands when it's heated. Less dense, so rises. Density = kg/m3

Radiation doe not need a material to transfer energy. Energy can be transferred through a vaccum

Density = mass / volume

efficiency = useful energy output (x100%) / total energy input

Energy from home is lost to the environment

Different types of insulation cost different amounts and save different amounts of energy

Payback time = cost of insulation /annual saving

Buildings that are energy efficient are well insulated; little energy is lost to the surroundings

Designers and architects have to make sure that little energy is lost

Spectrum of waves

Wave properties

Getting messages across

Amplitude - Maximum displacement of a particle from its rest position

Crest - Highest point

Trough - Lowest point

Wavelength - distance between two successive points having same displacement

Frequency - Number of complete waves passing a point in one second

wave speed - frequency x wavelength

Some optical instruments such as periscope use two or more plane mirrors

Refraction occurs because speed of waves decreases as wave enters a more dense medium and increases as the wave enters a less dense medium. Freq stays same but wavelength changes

Diffraction is the spreading out of a wave as it passes through a gap

Size of communications receiver depends on wavelength of radiation

Amount of diffraction depends on size of gap; the most diffraction occurs when the gap is a similar size to wavelengths. Effects are noticeable in telescopes and microscopes

Light and lasers

Morse code

Sending signals

Laser light

Critical angle

Endoscopy

Uses a series of dots and dashes to represent the alphabet. Used by signalling lamps as series of short and long flashes of light. Example of digital signal

When sent by light, electricity, microwaves or radio, almost instantaneous

Advantages and disadvantages. Can the signal be seen by others? Can the wire be cut? How far does the signal have to travel?

White light is made up of different colours of different freq. out of phase

Has only a single frequency, is in phase and shows low divergence

Used to read from the surface of a CD. As pitted, which represents digital signal, laser light is shone onto cd surface and reflection provides info for digital signal

Normally refraction happens when light travels from one material to another

If it's passing from a more dense material into less dense, the angle of refraction is lager than the angel of incidence

When angle is 90 degrees, the angel of incidence is called the critical angle

Total internal reflection - when the angle of incidence is bigger than the critical angle

Some fibres are coated to improve reflection

Allows doctors to see inside a body without the need for surgery. Light passes along one set of optical fibres to illuminate inside of the body, the light is reflected and then passes up another set of fibres to the eye/camera

Cooking and communicating using waves

Cooking with waves

Electromagnetic spectrum

Microwaves

Microwave radiation is used to communicate over long distances. The transmitter and receiver must be in line of sight.

Infrared radiation doesn't penetrate food easily

Microwaves penetrate up to 1cm into food

Microwaves can penetrate glass or plastic but are reflected by shiny metal surfaces. Special glass in a microwave open door reflects them and they can cause body tissue to burn

Energy is transferred by waves; the amount of energy depends on the frequency or wavelength of the wave

High frequency (short wavelength) waves transfer more energy

Ovens cook food by infrared radiation; energy is absorbed by the surface of food, the kinetic energy of the surface increases, the rest of the food is heated by conduction

Microwave ovens cook by microwave radiation- the water/fat molecules in the outer layers of food vibrate more

Microwaves have wavelengths between 1mm and 30cm

Phones use longer wavelengths than microwave ovens, less energy is transferred

Satellites are used for microwave communication. Signal from Earth is received, amplified and re-transmitted back to Earth. They're in line of sight because there are no obstructions in space.

Microwaves do not show much diffraction, adverse weather and large areas of water can scatter the signals, the curvature of the Earth limits the line of sight so transmitters have to be on high buildings.

Mobile phones can interfere with sensitive equipment -this is why they are banned on planes and in hospitals.

Wireless signals

Radio refraction and interference

Radio reflection

Communication problems

Wireless technology is used by radio and television, laptops, mobile phones

Radio waves are reflected and refracted in the Earth's atmosphere: the amount of refraction depends on the frequency of the wave/there is less refraction at higher frequencies

Radio stations broadcast signals with a particular frequency

The same frequency can be used by more than one radio station; the radio stations are too far away from each other to interfere/but in unusual weather conditions, the radio waves can travel further and broadcasts interfere

Digital Audio Broadcasting or DAB also provides a greater choice of radio stations but the audio quality isn't as good as the FM signals. DAB eliminates interference between other radio stations

Radio waves are reflected in the ionosphere. They behave like light in an optical fibre and undergo total internal reflection

Water reflects radio waves but land mass doesn't

Continued reflection by the ionosphere and the oceans allows radio waves to be received from an aerial that is not in line of sight

Microwaves pass through the ionosphere

Microwave signals are received by orbiting satellites, amplified and retransmitted back to Earth

Communication satellites orbit above the equator and take 24 hours to orbit Earth

Radio waves are diffracted when they meet an obstruction

Refraction in the atmosphere needs to be thought about when sending a signal to a satellite

Transmitting aerial needs to send a focused beam to the satellite - aerial is small

Some energy lost from edge because of diffraction

Transmitted beam is slightly divergent

Stable Earth

Earthquake waves

Earth's insides

Tan or burn

Ozone depletion

A seismograph shows the different types of earthquake wave

L waves travel around the surface VERY slowly

P waves are longitudinal pressure waves: P waves travel through the Earth between 5km/s and 8km/s

S waves are transverse waves. They travel through the Earth at between 3 km/s and 5.5 km/s/

Can pass through solids and liquids

Can only pass through solids

P waves travel through the Earth and are refracted by the core

S waves are not detected on the opposite side of the Earth to an Earthquake. They can't travel through liquid, which means that it tells the scientists that the core is liquid

The paths that are taken by P waves help scientists figure out how big the Earth's core is

Tan- caused by the action of ultraviolet light on the skin

maximum time to spend in the sun = published normal burn time x SPF

People are becoming more aware of the dangers- like sunbeds

Cells in the skin produce melanin, a pigment which produces a tan

People with darker skin don't tan as easily because uv radiation is filtered out

Scientists didn't believe that there was a thinning of the ozone layer, they thought the instruments were faulty but they compared with others and were confident in their findings

Ozone is found in stratosphere

CFC gases (aerosols) destroy the ozone and thin it out. This increases danger to us

The ozone layer is at its thinnest above the South Pole because the chemicals work best in cold conditions

Scientists monitor the thickness by using satellities

Helps filter out UV radiation

Agreement to reduce CFC emissions

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