OCR Additional Science 13/11/2018 Radiation for Life OCR Additional Science W Richards The Weald School

13/11/2018 P4a: Sparks

An introduction – click here Static Electricity 13/11/2018 13/11/2018 An introduction – click here

Static Electricity + + - - + - + + + - - - + + - + - - 13/11/2018 Static electricity is when charge “builds up” on an object and then stays “static”. How the charge builds up depends on what materials are used: + + - - + - + + + - - - + + - + - -

Short Static Experiments 13/11/2018 13/11/2018 Try the following quick static electricity experiments: Rubbing a balloon on your jumper and “sticking” it to the wall Charging a plastic rod by rubbing it with a cloth and then holding it near the water from a smooth-running tap Charging a plastic rod and trying to pick up small pieces of paper (or someone else’s hair!) with it Rubbing a balloon on someone else’s head – you might want to ask their permission first… Can you explain what you saw in each of these experiments?

Static Electricity 13/11/2018 + - - -

Static Electricity in Lightning 13/11/2018 13/11/2018 e- e- e- e-

Van de Graaf generators 13/11/2018 13/11/2018 13/11/2018 When a charge is neutralised by the movement of electrons either from the Earth or to the Earth we call this “earthing”

Dangers of Static – fuelling lines 13/11/2018 13/11/2018 Dangers of Static – fuelling lines

P4b: Uses of Electrostatics 13/11/2018 P4b: Uses of Electrostatics

Using Static in Paint Sprayers 13/11/2018 13/11/2018 Connected to negative voltage Connected to positive voltage Why is the paint sprayer given a negative charge? Why is the car given a positive charge?

Uses of Static – Smoke Precipitators 13/11/2018 Chimney Negatively charged plates - - - - - - Positively charged grid + + +

Uses of Static - Defibrillators 13/11/2018 How do defibrillators work?

13/11/2018 P4c: Safe Electricals

Electric Current 13/11/2018 13/11/2018 Electric current is a flow of negatively charged particles (i.e. electrons). Note that electrons go from negative to positive - + e- By definition, current is “the rate of flow of charge” and it is larger through shorter, wider wires e-

Resistance V R I Resistance = Voltage (in V) (in ) Current (in A) Georg Simon Ohm 1789-1854 13/11/2018 Resistance is anything that will RESIST a current. It is measured in Ohms, a unit named after me. Basically, longer wires have more resistance and wider wires have less resistance. The resistance of a component can be calculated using Ohm’s Law: V R I Resistance = Voltage (in V) (in ) Current (in A)

An example question: Ammeter reads 2A A V 13/11/2018 Ammeter reads 2A V A What is the resistance across this bulb? Assuming all the bulbs are the same what is the total resistance in this circuit? Voltmeter reads 10V

What is the resistance of these bulbs? More examples… 13/11/2018 3A 6V 12V 4V 2A 1A 2V 3A What is the resistance of these bulbs?

Resistance Resistance is anything that opposes an electric current. 13/11/2018 13/11/2018 13/11/2018 Resistance is anything that opposes an electric current. Resistance (Ohms, ) = Potential Difference (volts, V) Current (amps, A) What is the resistance of the following: A bulb with a voltage of 3V and a current of 1A. A resistor with a voltage of 12V and a current of 3A A diode with a voltage of 240V and a current of 40A A thermistor with a current of 0.5A and a voltage of 10V 3 4 6 20

The neutral wire of a plug is used to complete the circuit. Wiring a plug 13/11/2018 1. 2. 3. 4. 5. 6. Earth wire Live wire Fuse Neutral wire Cable grip Insulation The neutral wire of a plug is used to complete the circuit. The Earth wire of a plug keeps the device safe by stopping the appliance becoming “live”

Words – large, harm, safety, melt, live, circuit, fuse Fuses 13/11/2018 Fuses are _______ devices. If there is a fault in an appliance which causes the ____ and neutral (or earth) wire to cross then a ______ current will flow through the _____ and cause it to _____. This will break the _______ and protect the appliance and user from further _____. Words – large, harm, safety, melt, live, circuit, fuse

Circuit breakers 13/11/2018 Residual Current Circuit Breakers (RCCBs) are often used with fuses. They have some advantages over fuses: They are safer – they don’t get hot They react more quickly They can be switched off for repairs They are easy to reset Each RCCB is attached to a certain circuit, so if one switches off you can see which circuit has a fault

Words – fuse, fault, metal, surges, touch Earth wires 13/11/2018 Earth wires are always used if an appliance has a _____ case. If there is a _____ in the appliance, causing the live wire to ______ the case, the current “_______” down the earth wire and the ______ blows. Earth wires are not needed if a device is “double insulated”. Words – fuse, fault, metal, surges, touch

Power and fuses 13/11/2018 13/11/2018 Power is “the rate of doing work”. The amount of power being used in an electrical circuit is given by: P I V Power = voltage x current in W in V in A Using this equation we can work out the fuse rating for any appliance. For example, a 3kW (3000W) fire plugged into a 240V supply would need a current of _______ A, so a _______ amp fuse would be used (fuse values are usually 3, 5 or 13A).

Power and fuses Copy and complete the following table: Appliance 13/11/2018 13/11/2018 Copy and complete the following table: Appliance Power rating (W) Voltage (V) Current needed (A) Fuse needed (3, 5 or 13A) Toaster 920 230 Fire 2000 Hairdryer 300 Hoover 1000 Computer 100 Stereo 80

Power and fuses Copy and complete the following table: Appliance 13/11/2018 13/11/2018 Copy and complete the following table: Appliance Power rating (W) Voltage (V) Current needed (A) Fuse needed (3, 5 or 13A) Toaster 920 230 4 5 Fire 2000 8.7 13 Hairdryer 300 1.3 3 Hoover 1000 4.3 Computer 100 0.43 3 or 1 Stereo 80 0.3

13/11/2018 P4d: Ultrasound

Waves- Some definitions… 13/11/2018 1) Amplitude – this is “how high” the wave is: 2) Wavelength () – this is the distance between two corresponding points on the wave and is measured in metres: 3) Frequency – this is how many waves pass by every second and is measured in Hertz (Hz)

Transverse vs. longitudinal waves 13/11/2018 Transverse waves are when the displacement is at right angles to the direction of the wave (e.g. light and other electromagnetic waves)… Displacement Direction Displacement Longitudinal waves are when the displacement is parallel to the direction of the wave (e.g. sound waves)… Direction Where are the compressions and rarefactions?

Words – depth, reflected, picture, medium Ultrasound 13/11/2018 Ultrasound is the region of sound above 20,000Hz – it can’t be heard by humans. It can be used in pre-natal scanning: How does it work? Ultrasonic waves are partly _________ at the boundary as they pass from one _______ to another. The time taken for these reflections can be used to measure the _______ of the reflecting surface and this information is used to build up a __________ of the object. Words – depth, reflected, picture, medium

Other uses of ultrasound 13/11/2018 1) Breaking down kidney stones Ultrasonic waves break kidney stones into much smaller pieces 2) Cleaning (including teeth) Ultrasound causes dirt to vibrate dirt off without damaging the object Why is ultrasound better than X-rays? Ultrasound can be used instead of X-rays because they are able to produce images of soft tissue and they do not damage living cells.

P4e: What is Radioactivity? 13/11/2018 P4e: What is Radioactivity?

The structure of the atom 13/11/2018 ELECTRON – negative, mass nearly nothing PROTON – positive, same mass as neutron (“1”) NEUTRON – neutral, same mass as proton (“1”)

Introduction to Radioactivity 13/11/2018 Some substances are classed as “radioactive” – this means that they are unstable and continuously give out radiation: Radiation The nucleus is more stable after emitting some radiation – this is called “radioactice decay” and the activity is measured in “Becquerels (Bq)”.

Types of radiation 13/11/2018 1) Alpha () – an atom decays into a new atom and emits an alpha particle (2 protons and 2 ______ – the nucleus of a ______ atom) Unstable nucleus New nucleus Alpha particle 2) Beta () – an atom decays into a new atom by changing a neutron into a _______ and electron. The fast moving, high energy electron is called a _____ particle. Beta particle New nucleus Unstable nucleus 3) Gamma – after  or  decay surplus ______ is sometimes emitted. This is called gamma radiation and has a very high ______ with short wavelength. The atom is not changed. Words – frequency, proton, energy, neutrons, helium, beta Unstable nucleus New nucleus Gamma radiation

Changes in Mass and Proton Number 13/11/2018 Alpha decay: Am 241 95 Np 237 93 α 4 2 + Beta decay: Sr 90 38 Y β -1 + 90 39

Ionisation 13/11/2018 Radiation is dangerous because it “ionises” atoms – in other words, it turns them into ions by “knocking off” electrons: Alpha radiation is the most ionising (basically, because it’s the biggest). Ionisation causes cells in living tissue to mutate, usually causing cancer.

Half life 13/11/2018 The decay of radioisotopes can be used to measure the material’s age. The HALF-LIFE of an atom is the time taken for HALF of the radioisotopes in a sample to decay… = radioisotope = new atom formed After 2 half lives another half have decayed (12 altogether) After 3 half lives another 2 have decayed (14 altogether) After 1 half life half have decayed (that’s 8) At start there are 16 radioisotopes

A radioactive decay graph 13/11/2018 13/11/2018 Activity (Bq) “1 Becquerel” means “1 radioactive count per second” Time

A radioactive decay graph 13/11/2018 Count 1 half life 1 half life 1 half life Time

P4f: Uses of Radioisotopes 13/11/2018 P4f: Uses of Radioisotopes

Background Radiation 13% are man-made Radon gas Food Cosmic rays 13/11/2018 13/11/2018 13% are man-made Radon gas Food Cosmic rays Gamma rays Medical Nuclear power

Background Radiation by Location 13/11/2018 In 1986 an explosion occurred at the Chernobyl nuclear power plant. Here is a “radiation map” showing the background radiation immediately after the event: Other “risky” areas could be mining underground, being in a plane, working in an x-ray department etc

Uses of radioisotopes - tracers 13/11/2018 A tracer is a small amount of radioactive material used to detect things, e.g. a leak in a pipe: Gamma source The radiation from the radioactive source is picked up above the ground, enabling the leak in the pipe to be detected.

Uses of radioactivity – smoke detectors 13/11/2018 Smoke detectors Alpha emitter +ve electrode -ve electrode Alarm Ionised air particles If smoke enters here a current no longer flows

Uses of radioactivity – dating rocks 13/11/2018 Question: Uranium decays into lead. The half life of uranium is 4,000,000,000 years. A sample of radioactive rock contains 7 times as much lead as it does uranium. Calculate the age of the sample. Answer: The sample was originally completely uranium… 1 half life later… 1 half life later… 1 half life later… 8 4 8 2 8 1 8 …of the sample was uranium Now only 4/8 of the uranium remains – the other 4/8 is lead Now only 2/8 of uranium remains – the other 6/8 is lead Now only 1/8 of uranium remains – the other 7/8 is lead So it must have taken 3 half lives for the sample to decay until only 1/8 remained (which means that there is 7 times as much lead). Each half life is 4,000,000,000 years so the sample is 12,000,000,000 years old.

An exam question… 13/11/2018 Potassium decays into argon. The half life of potassium is 1.3 billion years. A sample of rock from Mars is found to contain three argon atoms for every atom of potassium. How old is the rock? (3 marks) The rock must be 2 half lives old – 2.6 billion years

Carbon Dating 13/11/2018 The amount of the isotope Carbon-14 present in the air has not changed for thousands of years. Therefore scientists can use it to help calculate how old something is. Consider, for example, a fossilised tree: 1) When the tree died it stopped exchanging carbon-14 with the atmosphere 2) As time went on the amount of carbon-14 decreased as it decayed 3) The amount of current activity can then be compared to a living tree to work out how old it is

13/11/2018 P4g: Treatment

X-Rays and Gamma Rays 13/11/2018 X-rays and gamma rays are similar in that they have similar wavelengths and they are both ionising but they are produced in different ways. Gamma rays are given out from the nucleus of radioactive materials whereas X-rays are made by firing high-speed electrons at metal targets and are therefore easier to control. X-ray images are possible because the absorption of X-rays depends on the material’s thickness and density.

Uses of Radioactivity - sterilisation 13/11/2018 13/11/2018 Gamma rays can be used to kill and sterilise germs without the need for heating. The same technique can be used to kill microbes in food so that it lasts longer.

Uses of Radioactivity - Treating Cancer 13/11/2018 13/11/2018 High energy gamma radiation can be used to kill cancerous cells. However, care must be taken in order to enure that the gamma radiation does not affect normal tissue as well. During radiotherapy gamma rays are focused on the tumour and rotated around the patient with the tumour at the centre, thereby limiting damage to non-canerous tissue.

Uses of radioactivity – medical tracers 13/11/2018 As well as using tracers to find leaks in pipes, tracers can also be used in medicine to highlight problem areas within a body by using a radiation detector: What sort of half life would you want a medical tracer to have? Medical radioisotopes are produced by placing materials in a nuclear reactor and they become radioactive by absorbing extra neutrons.

Radiation dose is measured in units called “sieverts” (Sv). Exposure to Radiation 13/11/2018 People like me work with radiation a lot so we need to wear a “dosimeter” to record our exposure to radiation: Radiation dose is measured in units called “sieverts” (Sv).

13/11/2018 P4h: Fission and Fusion

How Power Stations Work 13/11/2018 1) A fossil fuel is burned in the boiler 2) Water turns to steam and the steam drives a turbine (in some gas poer stations the air is heated directly) 3) The turbine turns a generator 4) The output of the generator is connected to a transformer 5) The steam is cooled down in a cooling tower and reused

Nuclear power stations 13/11/2018 13/11/2018 Notice that the heat from these reactions is used to heat water and turn it into steam, which then drives turbines.

Nuclear fission More neutrons Neutron Uranium or plutonium nucleus 13/11/2018 More neutrons Neutron Uranium or plutonium nucleus Unstable nucleus New nuclei (e.g. barium and krypton)

Chain reactions 13/11/2018 Each fission reaction releases neutrons that are used in further reactions. A nuclear bomb is basically a chain reaction that has gone out of control!!

Fission in Nuclear power stations 13/11/2018 These fission reactions occur in the fuel rods and they become very hot. Water (a coolant) cools the rods (which then turns to steam) and the control rods are moved in and out to control the amount of fission reactions taking place.

Nuclear Fusion in stars 13/11/2018 13/11/2018 Proton Neutron Nuclear fusion happens in stars but it’s not possible to use it in power stations yet as it needs temperatures of around 10,000,000OC and very high pressures.

Stanley Pons and Martin Fleishmann Cold Fusion 13/11/2018 13/11/2018 Stanley Pons and Martin Fleishmann In 1989 we claimed that we had enabled “cold fusion”, i.e. we had created fusion reactions in lab temperatures. However, no one else could verify our findings so our theories have not been accepted.