GCSE Physics P4 (OCR B722): Radiation for Life

Year 11 revision topics

P4a Sparks
1. Recognise that when some materials are rubbed they attract other objects:
• certain types of dusting brushes become charged and attract dust as they pass over it.
• Recognise that insulating materials can become charged when rubbed with another insulating material.
1. Be able to state that there are two kinds of electric charge:
• positive
• negative.
1. Be able to describe how you can get an electrostatic shock from charged objects
• eg synthetic clothing.
1. Be able to describe how you can get an electrostatic shock if you become charged and then become earthed
• eg touching water pipes after walking on a floor covered with an insulating material like synthetic carpet.
• Know that like charges repel and unlike charges attract.
• Understand that electrostatic phenomena are caused by the transfer of electrons, which have a negative charge.
1. Be able to describe static electricity in terms of the movement of electrons:(HT)
• a positive charge due to lack of electrons
• a negative charge due to an excess of electrons.
• Know that atoms or molecules that have become charged are called ions.(HT)
1. Be able to explain how static electricity can be dangerous when:
• in atmospheres where explosions could occur eg inflammable gases or vapours or with high concentrations of oxygen
• in situations where large quantities of charge could flow through the body to earth.
1. Be able to explain how static electricity can be a nuisance:
• dirt and dust attracted to insulators (plastic containers, TV monitors etc)
• causing clothing to 'cling'.
• Be able to explain how anti-static sprays, liquids and cloths help reduce the problems of static electricity. (HT)
1. Be able to explain how the chance of receiving an electric shock can be reduced by:(HT)
• correct earthing
• use of insulating mats
• using shoes with insulating soles
• bonding fuel tanker to aircraft.
P4b Uses of electrostatics
1. Know that electrostatics can be useful for electrostatic precipitators:
• remove the dust or soot in smoke
• used in chimneys.
1. Know that electrostatics can be useful for spraying:
• spray painting
• crop spraying
• Know that electrostatics can be useful for restarting the heart when it has stopped (defibrillator).
• Know that defibrillators work by discharging charge.
1. Be able to explain how static electricity can be useful for electrostatic dust precipitators to remove smoke etc from chimneys:
• dust passes through charged metal grid or past charged rods
• dust particles become charged
• plates are earthed or charged opposite to grid
• dust particles are attracted to the plates.
• plates struck and dust falls to collector
1. Be able to explain how static electricity is used in electrostatic dust precipitators to remove smoke particles etc from chimneys:(HT)
• high voltage metal grids put into chimneys to produce a charge on the dust
• dust particles gain or lose electrons
• dust particles induce a charge on the earthed metal plate
• dust particles attracted to the charged plates
1. Be able to explain how static electricity can be useful for paint spraying:
• spray gun charged
• paint particles charged the same so repel giving a fine spray and coat
• object charged oppositely to paint so attracts paint into the 'shadows' of the object giving an even coat with less waste.
• Be able to explain how static electricity is used in paint spraying, in terms of paint and car gaining and losing electrons and the resulting effects(HT)
1. Be able to explain how static electricity can be useful for restarting the heart when it has stopped (defibrillator):
• paddles charged
• good electrical contact with patient's chest
• charge passed through patient to make heart contract
• care taken not to shock operator.
P4c: Safe electricals
• Be able to explain the behaviour of simple circuits in terms of the flow of electric charge.
• Be able to describe and recognise how resistors can be used to change the current in a circuit.
1. Be able to describe how variable resistors can be used to change the current in a circuit:
• longer wires give less current
• thinner wires give less current (rheostat configured as a variable resistor only).
• Know that resistance is measured in ohms.
1. Know the colour coding for live, neutral and earth wires:
• live - brown
• neutral - blue
• earth - green/yellow.
• Know that an earthed conductor cannot become live.
• Be able to describe reasons for the use of fuses and circuit breakers (as re-settable fuses).
• Know and understand that 'double insulated' appliances do not need earthing.
1. Be able to explain how variable resistors can be used to change the current in a circuit:
• longer wires have more resistance
• thinner wires have more resistance (rheostat configured as a variable resistor only).
1. Be able to describe the relationships between current, voltage (pd) and resistance:
• for a given resistor, current increases as voltage increases and vice versa
• for a fixed voltage, current decreases as resistance increases and vice versa.
• Be able to use the equation: resistance = voltage / current
1. Be able to use and apply the equation, including a change of subject:(HT)
• resistance (R) = voltage(V) / current (I)
• eg R = V/I, V = IR and I = V/R
1. Be able to describe the functions of the live, neutral and earth wires:
• live - carries the high voltage
• neutral - completes the circuit
• earth - a safety wire to stop the appliance becoming live.
1. Be able to explain how a wire fuse reduces the risk of fire; if the appliance develops a fault:
• too large a current causes the fuse to melt
• preventing flow of current
• prevents flex overheating and causing fire
• prevents further damage to appliance.
• Be able to use the equation: power = voltage × current
1. Be able to explain why 'double insulated' appliances do not need earthing:
• the appliance is a non conductor and cannot become live.
• Be able to explain the reasons for the use of fuses and circuit breakers as re-settable fuses (structure and mode of operation not required).(HT)
• Be able to explain how the combination of a wire fuse and earthing protects people.(HT)
1. Use the equation, including a change of subject:
• power (P) = voltage (V) × current (I)
• to select a suitable fuse for an appliance.
• P = IV, V = P/I and I = P/V
P4d Ultrasound
1. Suggested practical and research activities to revise from
• Looking at ultrasound pictures and investigate the hearing range of pupils in the class.
• Investigating the properties of longitudinal waves.
• Use a slinky and/or rope to demonstrate wave behaviours.
• Use echoes from hard surfaces to develop the idea of reflection of sound, and calculation of distance surface (using the echo time and speed of sound).
• Know that ultrasound is a longitudinal wave.
1. Recognise features of a longitudinal wave:
• wavelength
• compression
• rarefaction.
1. Recognise that ultrasound can be used in medicine to the for diagnostic purposes:
• to look inside people by scanning the body
• to measure the speed of blood flow in the body
• (You are not expected to describe the Doppler effect).
1. Be able to describe features of longitudinal waves:
• wavelength
• frequency
• compression (a region of higher pressure)
• rarefaction (a region of lower pressure).
1. Be able to describe and compare the motion and arrangement of particles in longitudinal and transverse physical waves:(HT)
• wavelength, frequency , compression , rarefaction , amplitude.
• Know that the frequency of ultrasound is higher than the upper threshold of human hearing (20 000 Hz) because the ear cannot detect these very high frequencies.
• Know that ultrasound can be used in medicine for non-invasive therapeutic purposes such as to break down kidney and other stones.
1. Be able to explain how ultrasound is used in:(HT)
• body scans (reflections from different layers returning at different times from different depths)
• breaking down accumulations in the body such as kidney stones.
1. Be able to explain the reasons for using ultrasound rather than X-rays for certain scans:(HT)
• able to produce images of soft tissue
• does not damage living cells.
P4e: Radioactivity
• Know that the radioactivity or activity of an object is measured by the number of nuclear decays emitted per second.
• Know and understand why radioactivity decreases with time.
• Know that nuclear radiation ionises materials.
• Know that radiation comes from the nucleus of the atom.
• Be able to describe radioactive substances as decaying naturally and giving out nuclear radiation in the form of alpha, beta and gamma.
• Be able to explain and use the concept of half-life.
• Be able to interpret graphical data of radioactive decay to include a qualitative description of half-life.
1. Be able to explain ionisation in terms of:
• removal of electrons from particles
• gain of electrons by particles.
• Be able to interpret graphical or numerical data of radioactive decay to include calculation of half-life.(HT)
• Be able to explain why alpha particles are such good ionisers.(HT)
• Be able to describe radioactivity as coming from the nucleus of an atom that is unstable.
• Know that an alpha particle is a helium nucleus.
• Know that a beta particle is a fast moving electron.
1. Be able to describe what happens to a nucleus when an alpha particle is emitted:(HT)
• mass number decreases by 4
• nucleus has two fewer neutrons
• nucleus has two fewer protons
• atomic number decreases by 2
• new element formed.
1. Be able to describe what happens to a nucleus when a beta particle is emitted:(HT)
• mass number is unchanged
• nucleus has one less neutron
• nucleus has one more proton
• atomic number increases by one
• new element formed.
• Be able to construct and balance nuclear equations in terms of mass numbers and atomic numbers to represent alpha and beta decay.(HT)
P2f: Use of Radioisotopes
• Understand why background radiation can vary.
• Know that background radiation mainly comes from rocks and cosmic rays.
1. Know industrial examples of the use of tracers:
• to track dispersal of waste
• to find leaks/blockages in underground pipes
• to find the route of underground pipes.
• Know that alpha sources are used in some smoke detectors.
• Know that radioactivity can be used to date rocks.
1. Know that some background radiation comes from waste products and man-made sources eg waste from:
• industry
• hospitals.
• Be able to evaluate the relative significance of sources of background radiation.(HT)
1. Be able to describe how tracers are used in industry:
• radioactive material put into pipe
• progress tracked with detector above ground/outside pipe
• leak/blockage shown by reduction/no radioactivity after the point of blockage.
• Be able to explain why gamma radiation is used as an industrial tracer.(HT)
1. Be able to explain how a smoke detector with an alpha source works:
• smoke particles hit by alpha radiation
• less ionisation of air particles
• current is reduced causing alarm to sound.
• Be able to explain how the radioactive dating of rocks depends on the calculation of the uranium/lead ratio.
• Know that measurements from radioactive carbon can be used to find the date of old materials.
1. Be able to explain how measurements of the activity of radioactive carbon can lead to an approximate age for different materials:(HT)
• the amount of Carbon-14 in the air has not changed for thousands of years
• when an object dies (eg wood) gaseous exchange with the air stops
• as the Carbon-14 in the wood decays the activity of the sample decreases
• the ratio of current activity from living matter to the activity of the sample is used to calculate the age within known limits.
P4g: Treatment
1. Be able to describe some similarities and differences between X-rays and gamma rays:
• both are ionising electromagnetic waves
• have similar wavelengths
• are produced in different ways.
• Know that medical radioisotopes are produced by placing materials into a nuclear reactor.
1. Be able to describe uses of nuclear radiation in medicine, to include:
• diagnosis
• treatment of cancer using gamma rays
• sterilisation of equipment.
• Know that only beta and gamma radiation can pass through skin.
• Know that nuclear radiation can damage cells.
• Be able to describe the role of a radiographer and the safety precautions they must take.
• Know that materials absorb some ionising radiation.
• Know and understand how the image produced by the absorption of X-rays depends on the thickness and density of the absorbing materials.
1. Be able to explain how:(HT)
• gamma rays are given out from the nucleus of certain radioactive materials
• X-rays are made by firing high speed electrons at metal targets
• X-rays are easier to control than gamma rays.
• Be able to describe how materials can become radioactive as a result of absorbing extra neutrons.
• Be able to explain why gamma (and sometimes beta) emitters can be used as tracers in the body.
• Understand why medical tracers should not remain active in the body for long periods.
1. Be able to explain how radioactive sources are used in medicine:(HT)
1. (i) to treat cancer:
• gamma rays focused on tumour
• wide beam used
• rotated round the patient with tumour at centre
• limiting damage to non-cancerous tissue.
2. (ii) as a tracer:
• beta or gamma emitter with a short half life
• drunk/eaten/ingested/injected into the body
• allowed to spread through the body
• followed on the outside by a radiation detector.
P2h Fision and Fusion
• Know that nuclear power stations use uranium as a fuel.
1. Be able to describe the main stages in the production of electricity:
• source of energy
• used to produce steam
• used to produce electricity.
• Be able to describe the process that gives out energy in a nuclear reactor as nuclear fission, and that it is kept under control.
• Know that nuclear fission produces radioactive waste.
1. Be able to describe the difference between fission and fusion:
• fission is the splitting of nuclei - making two smaller atoms
• fusion is the joining of nuclei - making a larger atom
• Know that one group of scientists have claimed to successfully achieve 'cold fusion'.
• Be able to explain why the claims are disputed - because other scientists could not repeat their findings.
1. Be able to describe how domestic electricity is generated at a nuclear power station:
• nuclear reaction
• producing heat
• heating water to produce steam
• spinning a turbine
• driving a generator.
1. Be able to describe what happens to allow uranium to release energy:(HT)
• uranium nucleus hit by neutron
• causes nucleus to split
• energy released
• more neutrons released.
• Know how the decay of uranium starts a chain reaction.
• Be able to describe a nuclear bomb as a chain reaction that has gone out of control.
1. Be able to explain what is meant by a chain reaction:(HT)
• when each uranium nucleus splits more than one neutron is given out
• these neutrons can cause further uranium nuclei to split.
1. Be able to explain how scientists stop nuclear reactions going out of control:(HT)
• rods placed in the reactor
• to absorb some of the neutrons
• allowing enough neutrons to remain to keep the process operating.
1. Be able to describe how nuclear fusion releases energy:
• fusion happens when two nuclei join together
• fusion produces large amounts of heat energy
• fusion happens at extremely high temperatures.
1. Be able to describe why fusion for power generation is difficult:
• requires extremely high temperatures
• high temperatures have to be safely managed.
• Understand why fusion power research is carried out as an international joint venture.
1. Be able to explain how different isotopes of hydrogen can undergo fusion to form helium:(HT)
• 11H + 21H ==> 32He
1. Understand the conditions needed for fusion to take place, to include:(HT)
• in stars, fusion happens under extremely high temperatures and pressures
• fusion bombs are started with a fission reaction which creates exceptionally high temperatures
• for power generation exceptionally high temperatures and/or pressures are required and this combination offers (to date) safety and practical challenges.
• Be able to explain why the 'cold fusion' experiments and data have been shared between scientists.
• Be able to explain why 'cold fusion' is still not accepted as a realistic method of energy production.(HT)

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