# Physics

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• Created by: Faolan
• Created on: 10-06-15 17:27
What do all waves have in common?
All waves transfer energy. All waves are produced as results of vibration. All sound travels through waves
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What is a longitudinal wave
A longitudinal wave is one, which the particles vibrate parallel to the direction in which the wave is travelling e.g. sound waves, ultrasound waves
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What are compressions in waves
Compressions are places where particles bunch together
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What are refractions in waves
Refractions are places where particles are further apart
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What are transverse waves
Transverse waves are where the particles vibrate perpendicular to direct ion to which the waves are travelling e.g. - Water waves - Waves on a rope - Electromagnetic
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What is the frequency of a waves
Of a wave is the number of complete waves that pass a point every second unit – Hertz HZ
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What is wavelength
Wavelength of a wave is the distance from on crest of a wave to the crest of the next wave
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What is amplitude
Is the maximum displacement of a wave from its undisturbed position?
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What is the time period
Time periods of a wave is the time taken for one complete wave to pass a point T= 1/f
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What is the equation for Velocity of a wave
Velocity= Frequency x Wave length
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What is Audible frequency?
Audible frequency is the range of Frequency humans hear
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What is the upper and lower limit which humans can hear
20 Hz → 20,000 Hz
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What are ultrasound waves
The ultrasound are sound waves greater than 20,000
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What is infrasound
Sound waves below the lower limit
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What are the medical uses of Ultra sound
Scanning the women’s womb to check on the development of the Foetus - Scanning soft tissues to diagnose cancers - Cleaning teeth
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What are the industrial uses of ultras sound
Scanning metal castings for faults or cracks - Fish location be sea trawlers - Mapping the surface of the ocean floor - Cleaning equipment
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What is an echo Principal
An echo is a reflected sound wave
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What can electromagnetic waves do?
•Can travel in a vacuum- this property is unique to electromagnetic waves • Travel at exactly the same speed in a vacuum •Are transverse waves
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What is the order of the electromagnetic spectrum
Gamma, X Rays, Ultra Violet, Visible light, Infrared light, Microwaves, Radio waves
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Explain light?
•Objects that produce lighht are luminous. We see such objects because light travels from the directly to our eyes • We see non-luminous objects only when they scatter (reflect) light from luminous objects into our eyes.
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What is the incident ray
The light ray striking the mirror is called the incident ray
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What is the normal
The normal is the imaginary line that meets the mirror at right angles at the point of incidence
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What is the reflected ray
The light ray travelling away from the mirror is called the reflected ray
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Descrive the image in a plane mirror
Virtual. The same size as the object. Laterally inverted. The same distance behind the mirror as the objects is in front
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What is refraction
Is the change in the direction of a beam of light as it travels from one material into another? It occurs because light travels at different speeds in different materials
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What is the definition of dispersion?
Dispersion is the breaking up of light into its components colours. Each colour in white light travels at the same speed in air, but at slightly different speeds in glass. This means that each colour bends by a slightly different amount when it refra
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What are the three different electrical properties
Good conductors, Semi-conductors, Poor conductors
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What are the properties of a good conductor
They have many free moving electrons and insulators have almost none.
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What are the properties of semiconductors
They have very few free moving electrons at room temperature, but considerably more at high temperatures
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What are examples of good conductors
Silver Copper Aluminium Steel
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What are examples of semi conductors
Silicon, Geranium
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What are examples of insulators
Plastic Rubber Wood Cork
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What happens when two insulators are rubbed together
They become electrically charged because the negatively charged electrons rub off on one material on to the other. The material that gains the electrons become negatively charged, the material that losses the electrons become positively charged.
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How can a charged conductor be discharged
It can be discharged by connecting it to the earth with a metal (conducting) wire or chain. The surplus of electrons moves down the chain to earth if the conductor is negatively charged. If the conductor is positively charged, electrons flow up from
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What is the law of static electricity
This states that opposite charges attract each other while objects with the same charge repel each other
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What is polarisation
When charged objects can attract uncharged objects. For example the charged screen of a television attracts dust.
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Static electricity is a nuisance and can pose a hazard, give examples
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Give an example of a precaution against static electricity
Computer engineers wear earthed wrist straps to reduce the responsibility to reduce the possibility of destroying computer chips
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How does conventional current flow
Conventional current flows from positive to negative
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How do electrons flow
Electrons flow from negative to positive
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What is charge measured in
Q is measure in coulombs C
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What is electric current measured in
I is the rate at which charge flows in a circuit, measured in amperes A
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What is the equation for charge
Q=I x t
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Which wire is neutral
Blue Wire
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Which wire it the live wire
Brown wire
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Which wire is the earth wire
Green and yellow
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Where is the fuse
Between the live terminal and the live pin
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What happens when the fuse heats up
It melts and breaks the circuit of too much current flows
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How is the cable secured
Using a cable grip
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What are the standard ratings most commonly used?
1A, 3A 5A and 13A
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Where must the fuse always be?
On the live side of the plug. If the was on the neutral side then the appliance would still be dangerously high voltage even when the fuse blows.
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How might you get an electric shock on something like a cooker
If the live wire inside an appliance comes loose and touches metal casings, you could an electric shock
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How does the earth wire protec1. List the planets that orbit the sun.
However the earth terminal is connected to the metal casing, so the current goes through the earth wire instead of causing an electric shock. The earth wire is very has a low resistance, so the current through it is very large. This breaks the fuse.
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Explain two way switches
In most two story houses you can turn on the landing lights on or off from upstairs or downstairs. To do this we need a two way switch.
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What is the calculation for the amount of energy used?
Number of kWh= number of kilowatts x number of hours.
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How does a direct current flow
It always flows in the same direction, from a fixed positive terminal
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How is the current in d.c. described
Unidirectional
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What is the alternating current
The electric supply to your home
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How is alternating current described
Bidirectional
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List the planets that orbit the sun.
Mercury, Venus, Mars, Jupiter, Saturn, Uranus and Neptune.
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What paths do all planets orbit the sun in
Elliptical
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What is the solar system
The sun and all the planets that orbit it also planets moons asteroids and comets.
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What are moons
They are Natural satellites of the planets. This means that moons orbit planets, just as the planets orbit the sun
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What are asteroids
Are lumps of rocks, ranging in size from 1km to 1000km across. Most orbit the sun n a “belt” between Mars and Jupiter. Sometime they can be thrown out of orbit and pass near earth
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What are comets
They are made up of ice and dust. They travel around the sun in elongated orbits. This means that sometimes they are very close to the sun and occasionally visible from earth, and sometimes they are very far away.
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What theory describes the solar system
It is best described by the heliocentric theory, because it places the sun at the centre.
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What did people used to believe in for about 500BC to the mid 17th century
People believed in the geocentric theory which placed the earth at the centre off the universe. They believed that the moons, mercury, Venus, the sun, mars Jupiter, Saturn and the stars all moved in circular (non elliptical) paths.
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What three major problems did this theory have
The strange looping motion (retrograde motion) of Jupiter and Saturn The phases of Mercury and Venus The apparent changes in the brightness of Venus and Mars.
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What theory did the Greek astronomer Ptolemy put forward?
He put forward the theory of epicycles to explain Jupiter’s loops. He believed that Jupiter moved in a circular motion path around a point that orbited the earth. He proposed that this caused the planet’s path to appear to loop back on itself.
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At around 1515 what theory did Nicholas Copernicus put forward
He put forward the heliocentric theory, which had all planets orbiting the sun in circular orbits. This challenged the Church that God had put the earth at the centre of the universe. Because the church was so powerful his ideas were not accepted.
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What was Isaac Newton’s explanation for what force causes the planet to orbit the sun?
Any two masses in the Universe attract each other, just as opposite poles of a magnet attract each other. - Increases with the masses of the objects - Decreases the further they are apart - Acts along the line joining their centres of mass
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When do gravitational forces become important
They become important when at least one of the masses is very large, like a planet or a star or a galaxy.
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What does gravity provide
It provides the centripetal forces for the orbital motion of the planets, asteroids and comets around the sun, for the moons round the planets, and for artificial satellites around the earth.
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The moon is a natural satellite of the earth, since the late 1950s, people have put artificial satellites into orbit around the earth. What are they mainly used for?
•Astronomy (hubble telescope) •Communications (TV broadcasts) • Weather monitoring/forecasting • Monitoring agriculture land use • Monitoring military activity, and general espionage.
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What can Geostationary sattelites also be called?
Geosynchronous satellites
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Where are they usually placed
About 36,000 km above the equator and take exactly 24 hours to orbit the Earth.
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What must these satellites do?
Orbit in the equatorial plane Orbit the earth in the same direction as the Earth spins on its axis They are also ideal for Telephone, microwave (mobile telephone) and TV communications Global positioning systems for use in sat navs
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What are satellites in low polar orbits ideal for
Taking photographs for weather forecasting Spying on military installations. Monitoring movements on the ice sheets at the North and South Poles
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What are the big advantages of astronomical telescopes
Take photographs without the blurring caused by the Earths atmosphere. View stars, planets and galaxies in greater detail Take photographs in the X-Rays, ultraviolet, infrared and radio wave part of the spectrum
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Describe the solar system in our galaxy
Our solar system contains only one star- the Sun. But as we look into the night skies we see add vast number of star systems. These make up our galaxy, the Milky Way. A typical galaxy contains around a billion stars.
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What is red shift
The light we observe form he distant galaxies has a longer wavelength than expected.
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What does red-shift tell us about the motion of these galaxies
These galaxies are moving away from us
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How is the earth structured?
The earth has an onion structure consisting of four layers. A solid outer crust floats on a thick, viscous mantle, while a liquid outer core surrounds a dense, solid inner core.
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How thick is the crust?
The crust is very thin- about 20km or so on average and is mainly basalt rock.
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How thick is the mantle?
It lies below the crust and is around 2900km thick. It consists mainly of silica and minerals of iron, magnesium and other metals.
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What is the lithosphere?
It is the crust and the upper, solid part of the upper mantle.
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What is the core made form?
It is mainly iron and nickel
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Why do we believe that the outer core is liquid?
By following the paths of the earthquakes waves as they travel though the Earth, we can tell that there is a change from solid to liquid about halfway through the earth.
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What else do earthquakes indicate?
That the Earth has a solid inner core
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What is believed to cause the heat inside the earth?
It is Radioactive decay. This heat causes the convection currents which causes the plates of the crust to move.
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The earth’s lithosphere is the crust and the upper part of the mantle, how is it cracked.
Into pieces called tectonic plates
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What does the word tectonic mean
It means “within the crust of the earth”
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What happens when these plates move
The continents move too
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How fast are the plates moving?
The move very slowly at about 1 or 2 cm per year
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What is at the boundary between tectonic plates?
Volcanic and/or earth earthquake activity
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What are three different way plates move past each other?
Sliding, colliding or separating
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Sometimes plates just slide past each other, what is the best known example of this
San Andreas fault in California. A narrow ***** of the coastline (along the edge off the Nazca plate) is sliding north while the North American plate is sliding south
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How do big plates of rock slide past each other?
They catch on each other and as the pressure builds up they can suddenly lurch and cause ad earthquake. This sudden lurch lasts only seconds but it can bring building down
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How do they minimise damage in earthquakes zones
They try to build earthquake-proof buildings that are designed to withstand a bit of shaking.
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Where do earthquakes usually bring more devastation
In poorer countries where there may be overcrowded cities, poorly constructed buildings and inadequate rescue services.
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## Other cards in this set

### Card 2

#### Front

What is a longitudinal wave

#### Back

A longitudinal wave is one, which the particles vibrate parallel to the direction in which the wave is travelling e.g. sound waves, ultrasound waves

### Card 3

#### Front

What are compressions in waves

### Card 4

#### Front

What are refractions in waves

### Card 5

#### Front

What are transverse waves