Physics (P4) GCSE Revision cards

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  • Created by: Beth
  • Created on: 11-02-13 16:33
what is the difference between like and unlike charges?
like charges repel and unlike charges attract
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what causes electrostatic phenomena?
electrostatic phenomena are caused by the transfer of electrons
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what is static electricity?
it is the movement of electrons
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decribe the different charges of static electricity:
- a positive charge due to lack of electrons; - a negative charge due to excess of electrons
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what are charges atoms or molecules called?
ions
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how can the chance of receiving an electric shock be reduced?
- with the correct earthing, - the use of insulating mats, - the use of shoes with insulating soles
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what can help reduce the build up of static charge electricity and how do these work?
anti-static sprays, liquids and cloths can help redce the build up by carrying the charge away through the conducting material
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when can static electricity be dangerous?
- in atmospheres where explosions could occur, - in situations where large quantities of charge could flow through the body to earth
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when can static electricity be a nuisance?
when dirt and dust attracted to insulators causing clothing to cling
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medically, how can static electricity be very useful?
it can be useful for restarting the heart when it has stopped (defibrillator)
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explain the process of a defibrillator?
paddles charged --> good electrical contact with the patients chest --> charge passed through the patiet to make the heart contract --> care taken not to shock the opperator
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Static electricity can be useful for electrostatic dust precipitators, what does this machine do, and state the process?
it removes smoke particles from chimneys. The process: - metal plates put into chimneys, with negative charge, - dust particles gain electrons as they move through the grid, - (negative)dust particles attracted to earthed plates, - dust falls
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how is charge acrried around a circuit?
by negatively charged electrons
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what is current measured in?
amperes (A)
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what does a resistor do?
it limits the amount of curent flowing in a circuit
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what is resistance measured in?
Ohms
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do longer, thinner wires have more or less resistance?
more - so allow less current to flow
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what is voltage measured in?
volts
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describe a live wire?
a live wire in a plug is brown and carries the current into the appliance
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decribe a neutral wire?
a neutral wire completes the circuit and is blue
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describe an earth wire?
an earth wire is green and yellow and carries charge away from the appliance if a fault causes the casing to become live
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what happens if a fault causes a surge in the circuit?
fuses break and prevent current from flowing, this stops overheating
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what are circuit breakers?
they are fuses which can be resetso they do not need replacing like fuses do.
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why do doube insulated wires not need an earth wire?
because they do not have any exposed metal parts so they cannot become live
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what does direct current mean?
it means that a current flows in one way from a battery
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why do mains electricity alternate?
so the electrons vibrate in both directions
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what is the resistance equation?
resistance = voltage/current
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what is the equation to find power?
power = voltage x current to select a fuse
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how is sound produced?
by vibrating particles
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decribe longditudinal waves?
they are waves that vibrate parallel to the motion of the wave (e.g. sound)
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decribe transverse waves?
they are waves that vibrate at right angles to the motion of the wave
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what is frequency?
it is the number of complete waves in a second, it is measured in Hertz, Hz
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what is ultrasound?
it is sound with a higher frequency than humans can hear
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what is the upper threshold for human hearing?
20,000 Hz
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what can ultrasound be used for?
it can be used to scan the body to make images of the organs, foetuses or tumours. It can also be used to break down kidney stones and break up cataracts in the eye
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where is radioactivity given out?
it is given out by the nucleus of a radioactive atom to make it more stable
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how can radioactivity be measured?
it can be measured by a Geiger-Muller tbe and activity is measured in Bequerels (Bq)
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does radioactivity increase or decrease over time?
it decreases
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what is the half-life of radioactivity?
it is the time taken for the activity to halve
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what is an alpha particle and what is it made of?
it is a helium nucleus and is made of 2 protons and 2 neurons. It has a charge of +2
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what is a beta particle and what is it's charge?
it is a high speed electron, which is very small with a charge of -1
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what happens in beta decay?
in beta decay, a neutron changes into a proton and an electron
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what kind of wave is gamma radiation?
gamma radiation is an electromagnetic wave
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what does ionising mean?
it means the ability to remove electrons from other atoms to create ions
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what is the mass number?
the mass number is the total number of protons and neutrons in an atom
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what is the atomic number?
the atomic number is the number of protons in an atom
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what is always conserved in nuclear equations?
the charge and mass
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what is background radiation?
it is ionising radiation that is always present in the environment
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where does background radiation come from?
it naturally comes from rocks and cosmic rays, but also from man made sources such as waste products from hospitals and industry
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why do radioisotopes use gamma radiation only?
because alpha and beta would not penetrate pipes/soil
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what do some rocks contain that can be used to find the age of the rock?
uranium
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living things contain Carbon-14, what happens when the plant or animal dies?
it decays to form Carbon-12
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how can some remains of animals and plants be dated?
by looking at the ratio of C-14 to C-12
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C-14 decays slowly, how does this effect it's ability to date dead material?
it means it cannot be used to date things less than a few hundred of years old
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what are x-rays and gamma rays both used for?
they are both used in medicinefor diagnosis and treatment.
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what are some similarities between x-rays and gamma rays?
they have similar wavelengths, and they are both ionising
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what is radiotherapy?
it is where radiation is used to kill cancer cells
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what happens if living cells absord ionising radiation?
they have an increased risk of becoming cancerous
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how do x-rays work?
they are absorbed by bones, so are passed through the body to give images of the skeleton. They cannot give detailed images of soft tissues.
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how are x-rays produced?
by electrons from a hot cathode hitting a metal target. They are easy to control as the machine produces them.
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where is gamma radiation given out?
it is given out from a radioactive material so is difficult to control
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give one use of gamma radiation?
to sterilise medical equipment
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how do radiographers limit their exposure to x-rays and gamma?
they leave the room when the radiation is switched on
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how is gamma mostly used?
it is used as a radioactive tracer to rpoduce images of inside the body and tunnels
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how does a power station use heat?
to make steam, to drive a turbine and to generate electricity
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how does a nuclear power station use uranium fuel?
it uses uranium fuel to create a fission reaction to produce the heat energy
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what is fission?
it is where a radioisotope splits into smaller ones and gives out energy
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what is a chain reaction within fission?
each fission reaction produces more neutrons which go onto create more fission reactions
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what is the main danger of a chain reaction?
it can become out of control and cause an explosion
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what do graphite rods do in a chain reaction?
they slow neutons down so they can be absorbed and carry on the chain reaction
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what do boron control rods do in a chain reaction?
they are lowered and raised to absorb some neutrons to prevent the reaction getting out of control
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how do stars get their energy?
from nuclear fusion, where light nuclei fuse together to make heavier ones
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what is nuclear fusion?
it is a reaction that produces large amounts of heat energy at extremely high temperatures
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why are fusion reactions hard to acheive on earth?
because extremely high teperatures are needed
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what type of fusion is currently not possible to acheive?
cold fusion
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Other cards in this set

Card 2

Front

what causes electrostatic phenomena?

Back

electrostatic phenomena are caused by the transfer of electrons

Card 3

Front

what is static electricity?

Back

Preview of the front of card 3

Card 4

Front

decribe the different charges of static electricity:

Back

Preview of the front of card 4

Card 5

Front

what are charges atoms or molecules called?

Back

Preview of the front of card 5
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