Flashcards in Unit 2B - Electricity And The Atom Deck (120):
What is the difference between the mains supply and battery?
Mains supply is AC and a battery is DC
What does AC stand for?
What does DC stand for?
What is the voltage and frequency for the UK mains supply?
230 volts, 50Hz
What's the difference between DC and AC?
DC means the current flows in one direction, AC means the current is constantly changing direction
What can be used to see the voltage of an AC supply?
Cathode ray oscilloscope
If you plug a AC supply into an oscilloscope what shape pattern will you get?
What is a time period?
The distance between two peaks on the oscilloscope
What is the formula for frequency?
Frequency = 1 / time period
What are the hazards of electricity in the home?
Long cable, frayed cables, cables in contact with something hot or wet, water near sockets, shoving things into sockets, damaged plugs, too many plugs into one sockets, lighting sockets without bulbs in and appliances without their covers on
How many wires are there in cables?
What colours are the different wires and what is there name?
Brown - live wire
Blue - neutral wire
Yellow - Earth wire
Which wire caries the voltage?
What is the earth wire for?
For safety in case something goes wrong
Why are the case, cable grip and cable made form rubber or plastics?
They are good insulators, keeping the electricity where it should be, and they are flexible to
What does earthing and fuses prevent?
If a fault happens and the live wire somehow touches the metal case what happens?
This causes an increase in current through the live wire, through the case and then out through the earth wire
What happens to the fuse in an electrical overload?
The big surge in current melts the fuse which isolates the appliance and breaks the circuit making it safe
How close should fuses operate above the current?
Just higher than the normal operating current
What does isolating the appliance do?
Make it impossible to get an electric shock or start a risk because of fire because of the heating effect of a large current
What does earthing mean?
A case that is attached to the earth wire
If the wire has a plastic coating and no metal aorta showing it is said to be?
What else can you use instead of a fuse?
What are circuits breakers?
They are an electrical safety devise that protect the circuit from damage if too much current flows
How do circuit breakers work?
When they detect a surge in current they break the circuit by opening a switch
What is a two advantages and a disadvantage of circuit breakers?
They can be easily reset by flicking a switch making them more convenient, they are faster as you don't have to wait for a fuse to melt however they are more expensive
Anything that supplies and transfers electricity also supplies and transfers?
If an appliance is efficient it?
Wastes less energy
What is the formula for energy transferred and power rating?
Energy transferred = power rating x time
What's the formula for electrical power with current and potential difference?
Power = current x potential difference
What is potential difference?
The energy transferred per charge passed
What's the formula for energy transformed?
Energy transformed = charge x potential difference
The bigger the change in potential difference the more or less energy transferred?
A battery with a bigger voltage will supply more?
Energy to the circuits for every coulomb of charge
What letter represent current?
What letter represents energy transformed?
What did Democritus think about atoms in the 5th century B.C?
All matter, no matter what it was, was made Jo of identical lumps of atomos
What did John Dalton say in 1804 about atoms?
He agreed with Democritus that matter was made up of tiny spheres (atoms) that couldn't be broken up, each element is made up of a different type of atom
Nearly 100 years after John Dalton what did JJ Thompson discover about electrons?
They could be removes from atoms so Dalton's theory wasn't quite right
What was the plum pudding theory?
Atoms were spheres of positive charges with tiny negative electrons stuck on them like plums in a plum pudding
Who came up with the nuclear model of an atom?
Rutherford and Marsden
What is the relative mass of an electron?
What is an isotope?
They are different forms of the same element, they have the same number of protons but different number of neutrons, same atomic number different mass number
What is an example of an isotope?
Carbon - 12 Carbon - 14
One one or two isotopes are stable the other ones are?
Radioactive which means they decay into other elements and give out radiation
Is radioactivity a predictable process?
No completely random
Can you stop a radioactive substance giving out radiation?
No you can't no matter what is done to them
Radioactivity is completely unaffected by?
Physical conditions like temperature or any sort of chemical bonding
What three types of radiation do radioactive substances give out?
Alpha, beta and gamma
What three things to background radiation come from?!?
Naturally occurring unstable isotopes which are all around us, in the air food and building materials, radiation from space called cosmic days and man - made sources like x rays and nuclear weapons
What is background radiation?
Naturally occurring radiation that is present at all times
What are alpha particles ?
Helium nuclei - 2 protons and 2 neutrons
What are beta particles?
What are gamma rays?
Very short wavelength electromagnetic waves
For every beta particle emitted what turns into what?
Neutron turns into a proton
How big are alpha and beta particles?
Alpha particles - relatively big
Beta articles - quite small
What is the penetration power of each type of radiation?
Alpha - low
Beta - medium
Gamma - high
How fast are alpha and beta particles?
Alpha - heavy and slow moving
Beta - quite fast
How far do each type of radiation travel in air?
Alpha - not far
Beta - quite a distance
Gamma - very far
How ionising are each type if radiation?
Alpha - strongly ionising because of there size they bash into lots of atoms and knock electrons off them which creates lots of ions
Beta - moderately ionising
Gamma - weakly ionising as they tend to pass through rather than colliding with atoms
What's the equation for the alpha decay of Uranium - 238 ?
238. 234. 4
U -------> Th. + He. + gamma rays
92 90. 2
What's the equation for beta decay of Carbon - 14?
14 14 0
C -------> N + e
6 7 -1
Damage causes by radiation depends on?
Radiation dose depends on the type and?
Amount of radiation
Radiation dose depends on?
Location and occupation
What underground rocks cause a higher radiation dose?
What radioactive active gas does granite release?
In a hospital who has a higher radiation dose?
Radiographs who use radiation to take x rays
Why do pilots have a higher than average radiation dose?
They fly at high altitudes and so are exposures to more cosmic rays
How to radiographs stop radiation from hurting them?
They wear lead aprons and stand behind lead screens to protect them from prolonged exposure
Nuclear industry and uranium miners are exposed to how much more radiation?
Ten times more
How to miners protect themselves from radiation?
Wear protective clothing and face masks to stop them touching or inhaling radioactive material they also go for regular check ups
What type of radiation are deflected by electric and magnetic fields?
Alpha and beta
Why are gamma radiation not deflected by electric or magnetic fields?
It has no charge
Are alpha and beta radiation deflected them same way?
No opposite way because of the opposite charges
Even through alpha particles have a larger charge why are beta particles deflected more?
Alpha particles have a much greater mass so aren't affects as much
What is half life?
Half life is the average time it takes for the number if nuclear in a radioactive isotope sample to halve
Does the radioactivity of a sample increase over time?
No it decreases
Why is half life used?
Measuring full life would be difficult as activity never reaches zero
What does a short and long half life mean?
Short half life - activity falls quickly and nuclei decay happens quickly
Long half life - activity falls more slowly and so most of the nuclei don't decay for a long time
What is radioactivity measured on?
What is the activity of half life measured in?
Becquerel - one becquerel means one nucleus decays per second
What radiation is used in smoke detectors?
How is an alpha source used in smoke detectors?
A weak alpha source is placed in the sectors close to two electrodes, the source cause ionisation so a current flows between the electrodes. When there is a fire smoke absorbs the alpha radiation stopping the current flowing and sounding the alarm
What radiative source can be used to see is the thyroid gland is working?
Iodine - 131
Why do isotopes which are taken into the body have to be gamma or beta and have a short half life ?
Gamma and beta can pass out of the body and alpha can't, and the radioactivity inside the patient quickly disappears
Radiotherapy is the?
Treatment of cancer using gamma rays
Gamma rays to treat cancer have to ?
Be directed carefully and the right dosage to only kill the cancer cells and not too many normal cells
If radiation kills normal cells you get?
Sterilisation of food and surgical instruments using which type of radiation?
How are gamma rays used to sterilise things?
High doses can kill microbes keeping food fresher for longer and kill microbes on surgical equipment
What is an advantage of using gamma rays to sterilise?
Gamma rays don't require high temperature so things like fresh apples and plastic instruments aren't damaged by it
How does radiation harm living cells?
Alpha, beta and gamma radiation enters living cells and collides with molecule knocking off electrons, these collision cause ionisation which damages and destroys the cells. It can also cause mutant cells to grow and divide uncontrollably a causing cancer
What source is most dangerous outside the body and why?
Beta and gamma is the most dangerous as it can get inside the body
Hat source is the most dangerous inside the body ?
Alpha because it can't pass straight out
What are the safety precautions taken when handling radioactive material?
Minimise your exposure, don't allow contact with skin, hold at arms length as far away from the body as possible with things, keep sources pointing away, store in lead boxes as lead absorbs radiation
What is nuclear fission?
The splitting up of a big atomic nuclei
What is nuclear fusion?
The joining of small atomic nuclei
How do nuclear power station generate electricity?
They use a nuclear reactor in which controlled chain reactions of atomic nuclei splitting up happens, this release energy in the form of heat.
What fuel is used at a nuclear power station?
Uranium - 235
Plutonium - 239
What happens for nuclear fusion to happen?
A slow moving neutron must be absorbed into a uranium or plutonium nucleus, the addition of this neutron makes the nucleus unstable causing it to split
What is the chain reaction in nuclear fission?
Each time uranium or plutonium nucleus splits up it spits out two or three neutrons which go on to hit other nuclei thus causing a chain reaction
In nuclear fission why are the new nuclei radioactive?
They have the wrong number if neutrons in the
What are the problems with nuclear power ?
The waste is highly radioactive so it can't just be thrown away, it is difficult and expensive to dispose of safely, decommissioning takes years, and nuclear power also carries the risk of radiation leaks from the plant
What happens in nuclear fusion?
Two light nuclei (e.g hydrogen) join together to create a larger nucleus
What would be an advantage of using nuclear fusion?
It doesn't leave behind radioactive waste and there is plenty of hydrogen for fuel
What's a big problem with using nuclear fusion?
It only happen at really high temperatures (10 000 000) and you need an extremely strong magnetic field to hold the hydrogen
Which one produces more energy nuclear fusion or fission?
Is it fusion or fission that happens inside of stars?
What are the different stages in the life cycle of star?
Protostar, main sequence star, red super giant, super nova, black hole, red giant, white dwarf and a black dwarf
What happens to form a protostar?
Stars initially form from clouds of dust, the force of gravity makes the dust and has spiral together to form a protostar
What happens to form a main sequence star from a protostar?
Gravitational energy converts to heat energy so the temperature rises, when the temperature is high enough hydrogen nuclei undergo nuclear fusion to form helium nuclei and give out massive amounts of heat and light. The heat created by nuclear fusion provides an outward pressure to balance the force of gravity pulling everything inwards, this is a long stable period the main sequence star
Why is the main sequence star so long?
There is massive amounts of hydrogen used as fuel
What happens when the hydrogen run out?
Heavier elements such as iron are made by nuclear fusion of helium causing the star it swell into a red giant or a super red giant
What size giant will the sun turn into?
Why are red giants red?
S the surface cools they become hot
What happens to a red giant ?
It becomes unstable and ejects its outer layer of dust and gas leaving behind a hit white core called a white dwarf, this cools down into a blacks dwarf and eventually disappears
What is the name of dust and gas that is ejected out of a red giant?
What happens to a red super giant to form a supernova?
Red super giants undergo more nuclear fusion and expand and contract servers times forming elements as heavy as iron in nuclear reactions. This explodes as a supernova forming heavier elements than iron and ejecting them to form new planets and stars