GCSE Physics P1

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  • Created by: Ruqayya11
  • Created on: 11-04-17 14:03
Energy Flow?
Energy, in the form of heat, flows from a warmer body to a colder body. When energy flows away from a warm object, the temperature of that object decreases
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Explain the difference between temperature and heat?
Temperature is a measure of hotness on an arbitrary scale. Heat is a measure of energy on an absolute scale
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How does a thermogram work?
A thermogram uses colour to represent temperature. Most heat lost from poorly insulated areas is indicated by the colours white / yellow / red. Least heat lost from well insulated areas indicated by the colours black / dark blue / purple
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Specific Heat Capacity?
The energy needed to raise the temperature of 1kg by 1*C (energy transferred = mass x specific heat capacity x temperature change)
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Specific Latent Heat?
The energy needed to boil 1kg of the material (energy transferred = mass x specific latent heat)
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How does double glazing reduce energy loss?
By conduction. The gap between the two pieces of glass is filled with a gar or contains a vacuum. Particles in a gas are far apart, so it is difficult to transfer energy and a vacuum does not contain particles
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Explain how loft insulation reduces energy loss by conduction and convection?
Warm air in the home rises and energy is transferred through the ceiling by conduction. Both sides of the ceiling are the same temperature so no energy is transferred. Without the insulation the warm air in the loft can move by convection
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Explain how cavity wall insulation reduces energy loss by conduction and convection?
The air in the foam is a good insulator and the air cannot move by convection because it is trapped in the foam
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Explain how shiny foil helps to keep a home warmer in winter and cooler in summer?
Energy is reflected back to keep the home cool in summer. Energy from the home is reflected back to keep the home warm in winter
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Conduction?
Conduction of heat is the process where vibrating particles pass on kinetic energy to neighbouring particles
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Why do metals conduct heat well?
Metals conduct well because some of their electrons are free to move. This makes transferring energy very fast
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Convection?
The fluid is heated and it expands. This makes the fluid less dense so it rises
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Why can't convection happen in solids?
Convection can't happen in solids because the particles can't move
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Radiation?
Heat can be transferred by radiation, as infrared waves (travel in straight lines at the speed of light)
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How is radiation difference from conduction and convection?
It doesn't need a medium to travel through, so it can occur in a vacuum. The amount of radiation emitted or absorbed depends on its surface colour and texture
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What is meant by the amplitude of the wave?
The maximum displacement of a particle from its rest position
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What is meant by the wavelength of the wave?
The distance between two successive points on a wave having the same displacement and moving in the same direction
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What is meant by the frequency of the wave?
The number of oscillations passing a point per second
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Electromagnetic Spectrum?
Radio, Microwave, Infrared, Visible, Ultraviolet, X-ray, Gamma Ray
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What does the size of a communications receiver depend on?
The wavelength of the wave; the longer the wavelength, the bigger the receiver. Radio waves need the biggest receivers, then microwaves...
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Why does refraction occur?
Refraction occurs because the speed of waves decreases as the wave enters a more dense medium and increases as the wave enters a less dense medium. The frequency stays the same but the wavelength changes
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What is diffraction?
Diffraction is the spreading out of a wave as it passes through a gap. The amount of diffraction depends on the size of the gap; the most diffraction occurs when the gap is a similar size to the wavelength. Larger gaps show less diffraction
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What is Morse Code?
Morse code uses a series of dots and dashes to represent letters. It is an example of a digital signal
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Why is Morse code an example of a digital signal and not an analogue signal?
As dots and dashes series of on and off signals; not continuously variable signal
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Laser Light and White Light?
White light is made up of different colours of different frequencies out of phase. Laser light has only a single frequency, is in phase and shows low divergence
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How is laser light used to read from the surface of a CD?
The surface of the CD is pitted, the pits represent the digital signal. Laser light is shone onto the CD surface and the difference in the reflection provides the information for the digital signal
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What is total internal reflection?
This is when the angle of incidence is bigger than the critical angle, and the light is reflected
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What is a critical angle?
This is when the angle of reflection is 90, the angle of incidence is called the critical angle
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What happens during endoscopy?
An endoscope allows doctors to see inside a body without the need for surgery, Light passes along one set of optical fibres to illuminate the body. The light is reflected and passes up another set of fibres to an eyepiece
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How is food cooked by infrared radiation?
Energy is absorbed by the surface of the food, the kinetic energy of the surface food particles increases. The rest of the food is heated by conduction
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How is food cooked by microwave radiation?
The water and fat molecules in the outer layes of food vibrate more. Microwaves penetrate upto 1cm into food
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How are satellites used for microwave communication?
The signal from Earth is received, amplified and re-transmitted back to earth. Satellites are in line of sight because there are no obstructions in space
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Why does signal strength for mobiles change a lot over a short distance?
Microwaves do not show much diffraction. Adverse weather and large areas of water can scatter the signal. The curvature of the earth limits the line of sight so transmitters have to be on tall buildings
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What happens when remote controls emit pulses of IR?
The LED at the front of the remote transmit the series of pulses. This is received by the device and decoded to allow the tv to change channels
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Optical Fibres?
Optical fibres allow data to be transmitted very quickly using pulses of light
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What is an analogue signal?
An analogue signal can take any value within a certain range. The frequency and amplitude of an analogue wave vary continuously
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Advantages of digital signals?
The signal remains high quality as the noise from amplifying the signal is easily removed
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What is multiplexing?
Multiplexing allows a large number of digital signals to be transmitted at the same time. It is another advantage of using digital technology
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What does the amount of refraction in the Earths atmosphere depend on?
The amount of refraction depends on the frequency of the wave. There is less refraction at higher frequencies
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Why can the same frequency 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 travel further and the broadcasts interfere
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How is interference reduced?
Interference is reduced if digital signals are used. DAB provides a greater choice of radio stations but the audio quality is no as good as the FM signals currently used. DAB eliminates interference between other radio stations
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Radio waves being reflected from the ionosphere?
They behave like light in an optical fibre and undergo total internal reflection. Continued reflection by the ionosphere and the oceans allow radio waves to be received from an aerial that is no in line of sight
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What does a seismograph show?
A seismograph shows the different types of earthquake wave. L waves travel round the surface very slowly
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P waves?
P waves are longitudinal pressure waves. P waves travel through the earth at between 5km/s and 8km/s. P waves can pass through solids and liquids
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S waves?
S waves are transverse waves. They travel through the earth at between 3km/s and 5.5km/s. S waves can only pass through solids
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How do P waves travel through Earth?
P waves are refracted by the core. The paths taken by P waves mean that scientists can work out the size of the Earth's core
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How do S waves travel through Earth?
S waves are not detected on the opposite side of Earth to an earthquake. They will not travel through liquid, which tells scientists that Earth's core is liquid
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How is a tan caused?
A tan is caused by the action of UV light on the skin. Cells in the skin produce melanin, a pigment that produces a tan
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Why do people with darker skin not tan as easily?
This is because darker skin absorbs more UV radiation. This prevent some of the damaging radiation from reaching the more vulnerable deeper tissues
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Explain how short hair increases the risk of skin cancer?
There is more skin exposed to UV light, which increases the risk of skin cancer
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What reduces the risk of skin cancer?
Using a sunscreen with SPF (maximum length of time to spend in Sun= published normal burn time x SPF)
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What reduces the thickness of the ozone layer?
CFCs gases from aerosols and fridges destroy ozone. Scientists monitor the thickness of the ozone layer using satellites
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Other cards in this set

Card 2

Front

Explain the difference between temperature and heat?

Back

Temperature is a measure of hotness on an arbitrary scale. Heat is a measure of energy on an absolute scale

Card 3

Front

How does a thermogram work?

Back

Preview of the front of card 3

Card 4

Front

Specific Heat Capacity?

Back

Preview of the front of card 4

Card 5

Front

Specific Latent Heat?

Back

Preview of the front of card 5
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