P4 - Radiation For Life Flashcards
P4 - Radiation For Life
Which direction do electrons move when a polythene rod is rubbed with a duster?
From duster to rod
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Which direction do electrons move when an acetate rod is rubbed with a duster?
From rod to duster
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What is a static charge caused by?
Electrons moving
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What happens if enough static charge builds up?
It can suddenly move which can cause sparks or shocks that may be dangerous.
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How can a charged conductor be discharged safely?
By connecting it to earth with a metal strap (earthing).
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How does earthing work?
Electrons flow down strap to ground if charge is negative and flow up strap from ground if positive.
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What are ions?
Atoms or molecules with a charge
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How does static attract dust?
Dust particles are charged and attract opposite charge. Objects in home are insulators (get easily charged) and attract dust.
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How does static affect clothing?
When synthetic clothes dragged (head or other clothes) electrons scrape off, leaving static charge - two attract. Little sparks/shocks as charges rearrange themselves.
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What causes shocks from door handles?
Walking on nylon carpet with insulating soles builds up charge. Touching metal door handle/water pipe allows charge to flow via conductor - little shock.
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How can static on clothing become dangerous?
Charge may become large enough to make a spark - dangerous near inflammable gases or fuel fumes.
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When can static become dangerous (other than on clothes)?
Fuel flowing out of pipe, paper drags on rollers or grain shoots out of pipe, static builds up. If too big, might spark - explosion in dusty/fumey places (petrol station).
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What kind of places is static dangerous in?
Areas with inflammable liquids or a high concentration of oxygen (hospital operating theatre)
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How do anti-static sprays work?
Make surface of a charged object conductive - provides an easy path for charges to move away.
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How do insulating mats and shoes work?
Prevent static electricity moving through them - stops human getting shocked.
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How do paint sprayers work?
Spray gun charged and object given opposite to attract. Paint drops repel each other (fine spray).
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What is the good thing about electrostatic paint sprayers?
Method gives even coat and hardly any paint wasted. No shadows - everywhere covered.
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How do dust precipitators work?
Smoke particles reach chimney bottom, meet wire grid/rods with high voltage and (-) charge. Dust particles gain electrons (become (-)) Dust particles induce charge on earthed metal plates Dust attracted to metal plates - stick forming larger particles When heavy enough, particles fall off/knocked off with hammer Falls and is removed
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How does a defibrillator work?
2 paddles to power supply: Paddles firmly on chest (good electrical contact) and charged up Everyone moves away - operator holds insulated handles Charge passes through paddles to patient - heart contracts.
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If you increase the voltage….
more current will flow
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If you increase the resistance…
less current will flow (or more voltage is needed to keep same current flowing)
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Current only flows when?
As long as there is a complete loop - broke circuit means no current.
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What does the live wire do?
Carries voltage. Alternates between a high + and - voltage of about 230V
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What colour is the live wire?
Brown
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What does the earth wire do?
Works together with fuse for safety
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What does the neutral wire do?
Completes tcircuit - electricity flows out through neutral - always at 0V.
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What colour is the neutral wire?
Blue
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What colour is the earth wire?
Green and yellow
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What must all appliances with metal cases be?
earthed
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What does double insulated mean?
If appliance has casing that is non-conductive (e.g. plastic) - doesn’t need earthing (never live)
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What happens is a fault develops where the live wire touches the metal case?
A big current flows through live wire. Surge blows fuse and causes wire inside to melt. Cuts off live supply by breaking circuit.
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When the fuse blows, what does this prevent?
Electric shocks by isolating appliance. Stops flex overheating which may cause fire. Prevent further damage to appliance.
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What is a circuit breaker?
Works like a fuse but can be reset and used again.
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How should fuses be rated?
As near as possible but just higher than normal operating current.
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What are the fixed fuse ratings?
3A, 5A and 13A
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What is a variable resistor?
Rheostat - resistor whose resistance can be changed by turning a knob.
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What are variable resistors good for?
Alternating the current flowing through a circuit. Turn up resistance, current drops (vice versa).
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Why do thinner wires increase resistance?
Electric charge has less space to move through.
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What is the resistance of a fixed resistor like?
Steady - at a constant temperature
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How is resistance calculated?
Voltage / current
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How is the ammeter set up in a circuit to measure resistance?
In series with other components
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How is the voltmeter placed in a circuit to measure resistance?
In parallel around component being tested.
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What is the official name for voltage around a test circuit?
Potential difference
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What are compressions?
Parts of a wave under high pressure (lots of particles)
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What are rarefactions in a wave?
Parts under low pressure (fewer particles)
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What is wavelength?
A full cycle of a wave from crest to crest/compression to compression
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What is frequency?
How many complete waves there are per second passing a certain point. Measured in hertz. Sound - high frequency=high pitch
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What is amplitude?
Measured from rest position to crest. Tells you how much energy wave is carrying, or how loud it is.
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How does a longitudinal wave move?
Vibrations are along same direction as wave is travelling
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How does a transverse wave move?
Vibrations are at 90 degrees to direction of travel of the wave
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What is ultrasound?
Electric devices can be made which produce electrical oscillations of any frequency. Easily converted into mechanical vibrations to produce longitudinal waves beyond range of human hearing.
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How does ultrasound work when breaking down accumulation in the body?
Removing kidney stones. High energy of ultrasound at stone turns it into sand like particles. Particles pass out of body in urine. Doesn’t need surgery and painless.
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How does ultrasound work in body scanning?
Waves pass through body but are reflected back when they meet a boundary between two different media. Echoes are processed by computer to produce video image.
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What advantages does ultrasound have?
Ultrasound is great for imaging soft tissue. Safer doesn’t damage cells.
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What do X-rays do compared to ultrasound?
Better for viewing bone. Can damage living cells by being ionising radiation, causing cancer at high doses.
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What are radioactive materials made up of?
Atoms with unstable nuclei that naturally decay at random
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What happens as radioactive material decays?
Give out alpha, beta and gamma. Nucleus often changes into new element.
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What is the relative atomic mass number?
Top number = number of protons and neutrons (AKA mass number)
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What is the atomic number?
Number of protons
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What is an isotope?
Atoms of same element with different mass numbers
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When does gamma radiation happen in decay?
After alpha and beta, if nucleus has extra energy to get rid of. Emits gamma ray that has no mass or charge - atomic and mass number don’t change.
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What is an alpha particle?
Helium nucleus of two protons and two neutrons
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What charge does an alpha particle have?
+2
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What mass does an alpha particle have?
4
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What happens to the mass number when a nucleus emits an alpha particle?
Decreases by 4 because it loses 2 protons and 2 neutrons
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What happens to the atomic number when the nucleus emits an alpha particle?
Decreases by 2 because it has 2 less protons
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What is a beta particle?
Fast moving electron
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What charge does a beta particle have?
-1
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What mass does a beta particle have?
0
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What happens to the mass number when a nucleus emits a beta particle?
Doesn’t change - lost a neutron but gained a proton
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What happens to the atomic number when a nucleus emits a beta particle?
Increases by 1 - has 1 more proton
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What happens as more unstable nuclei decay?
Radioactivity of the source as whole decreases - older a resource, less radiation emitted.
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What is the problem with trying to measure how quickly radioactive material decays?
Activity never reaches 0
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What is the definition of half life?
Time taken for half of the radioactive nuclei now present to decay.
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What does a short half life mean?
Activity falls quickly because lots of nuclei decay in a short time.
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What does a long half life mean?
Activity falls slowly, because most of nuclei doesn’t decay for a long time.
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What causes ionisation?
When some materials absorb ionising radiation - can enter living cells and interact with molecules.
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What does ionisation produce?
Charged particles called ions
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What is nuclear radiation and X-rays types of?
Ionising radiation
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What can X-rays and gamma rays do to electrons?
Transfer energy to electrons. Electrons then have enough energy to escape from atom, ionising it and leaving it positively charged.
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What can beta particles do to electrons?
Remove electrons from atom/molecule leaving them positively charged.
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What happens if a beta particle sticks to an atom?
Ionises it making it negatively charged.
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What can alpha particles do to electrons in an atom?
Remove electrons, making atom positive.
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Why are alpha particles good ionisers?
- Relatively large - easy to collide with atoms or molecules 2. Highly charged - easily remove electrons from atoms they pass or collide with.
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What do lower doses of ionising radiation tend to cause?
Minor damage without killing cells. Can give rise to mutant cells which divide uncontrollably - cancer.
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What can high doses of ionising radiation tend to do?
Kill cells completely, which causes radiation sickness if a lot of cells all get blasted at once.
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Which types of radiation are most dangerous outside the body?
Beta and gamma - can still get to delicate organs (pass through skin)
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Why is alpha not dangerous outside the body?
It can’t penetrate the skin
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Which source of radiation is most dangerous inside the body?
Alpha - do all their damage in a localised area, highly ionising.
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What sources of radiation are les dangerous inside the body?
Beta and gamma - less ionising, often pass straight out with very little damage
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What level of frequency do X-rays and gamma rays have?
High frequency
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What distance wavelength do X-rays and gamma rays have?
Short wavelength electromagnetic waves
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How are gamma rays made?
Released from some unstable atomic nuclei when they decay. No way to control when they are released.
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How are X-rays produced?
By firing high speed electrons at a heavy metal like tungsten. Much easier to control production of than gamma.
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What can X-rays pass easily through?
Flesh
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What can X-rays not pass easily through?
Thicker and denser material like bone or metal.
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What makes an X-ray image?
Varying amount of radiation that’s absorbed (denser materials absorb more X-rays)
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How is gamma used to treat cancer?
*Gamma focused on tumour using wide beam. *Beam rotated round patient - tumour at centre. *Minimises exposure of normal cells to radiation, reducing risk of damage to rest of body.
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What radiation can be used as medical tracers?
Radioactive isotopes that emit gamma (short half life - few hours)
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How can a patient be given a medical tracer?
Injected, drunk, eaten or ingested.
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How are medical tracers monitored?
Progress followed by radiation detector outside body.
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What is an example of a medical tracer?
Iodine-123 absorbed by thyroid gland and shows if thyroid is taking all iodine it should.
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Why must all isotopes in the body be beta or gamma?
Can penetrate tissue so are detectable outside. Can pass out easily.
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How can medical instruments be sterilised?
Exposing them to high dose of gamma radiation.
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Why does gamma radiation sterilise equipment?
It kills microbes
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What is the advantage of using radiation instead of water to sterilise equipment?
Doesn’t involve high temperatures. Plastic instruments can be sterilised without damaging them.
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How can radiation be used as tracers in industry?
Tracks movement of waste material to find route underground of pipes or detect leaks/blockages
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How is a leak detected using a radioactive tracer?
If detection of radioactivity stops/reduces must be a blockage/leak.
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What must the isotope be for industrial tracers?
Gamma emitters so it can be detected through metal/pipe. Needs short half life.
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Why does the industrial tracer need a short half life?
So it doesn’t cause a hazard if it collects somewhere. Doesn’t pollute water.
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What source is used in a smoke detector?
A weak alpha source close to two electrodes.
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How does a smoke alarm work?
In a fire, smoke particles are hit by alpha particles (less ionising of air) so current reduces, alarm sounds.
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How does background radiation come from radioactivity of naturally occurring unstable isotopes?
All around us. In air, food, building materials and rocks. Large proportion of background radiation comes from natural sources.
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How does background radiation come from space?
Known as cosmic rays. Come mostly from sun.
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How does background radiation come from human activity?
E.g. Fallout from nuclear explosions, waste from industry and hospitals. Represents a small proportion of total.
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How can the amount of background radiation vary?
Depending on where you are or job you have.
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What 3 ways do we receive background radiation?
Naturally occurring unstable isotopes. Space. Human activity.
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How can you work out the age of something using radioactive dating?
Measuring amount of radioactive isotope left in sample, and knowing its half life.
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What fraction of the carbon in the air does carbon-14 make up?
1/10,000,000 (one ten-millionth)
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What is the half life of carbon-14?
5730 years.
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What happens when carbon-14 isotopes die?
Stop exchanging gas with air outside atmosphere and is trapped inside. Gradually decays.
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How does uranium have a different half life?
Very long. Decay via series of short lived particles to produce stable isotopes of lead.
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What is produced after 1 half life of uranium?
50% uranium 50% lead
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What is produced after 2 half lives of uranium?
25% uranium 75% lead
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What is the equation for two hydrogen isotopes combining to form helium?
What is the equation for two hydrogen isotopes combining to form helium?
