2. 22/11/2016 OCR Additional Science W Richards Radiation for Life

3. 22/11/2016 P4a: Sparks

4. 22/11/2016 Static Electricity An introduction – click here

5. 22/11/2016 Static Electricity 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: + - + - + + - - - + + + - - + + + - - -

6. 22/11/2016 Short Static Experiments 22/11/2016 Try the following quick static electricity experiments: 1)Rubbing a balloon on your jumper and “sticking” it to the wall 2)Charging a plastic rod by rubbing it with a cloth and then holding it near the water from a smooth-running tap 3)Charging a plastic rod and trying to pick up small pieces of paper (or someone else’s hair!) with it 4)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?

7. 22/11/2016 Static Electricity + + + - - - - - - - - -

8. 22/11/2016 Static Electricity in Lightning 22/11/2016 e-e- e-e- e-e- e-e-

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

10. 22/11/2016 Dangers of Static – fuelling lines

11. 22/11/2016 P4b: Uses of Electrostatics

12. 22/11/2016 Using Static in Paint Sprayers Connected to negative voltage Connected to positive voltage 1)Why is the paint sprayer given a negative charge? 2)Why is the car given a positive charge?

13. 22/11/2016 Uses of Static – Smoke Precipitators - - - - - - + + + Chimney Negatively charged plates Positively charged grid

14. 22/11/2016 Uses of Static - Defibrillators How do defibrillators work?

15. 22/11/2016 P4c: Safe Electricals

16. 22/11/2016 Electric Current Electric current is a flow of negatively charged particles (i.e. electrons). Note that electrons go from negative to positive -+ e-e- e-e- By definition, current is “the rate of flow of charge” and it is larger through shorter, wider wires

17. 22/11/2016 Georg Simon Ohm 1789-1854Resistance The resistance of a component can be calculated using Ohm’s Law: Resistance = Voltage (in V) (in  )Current (in A) V RI 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.

18. 22/11/2016 An example question: V A 1)What is the resistance across this bulb? 2)Assuming all the bulbs are the same what is the total resistance in this circuit? Voltmeter reads 10V Ammeter reads 2A

19. 22/11/2016 More examples… 12V 3A 6V 4V 2A 1A 2V What is the resistance of these bulbs?

20. 22/11/2016 Resistance Resistance is anything that opposes an electric current. Resistance (Ohms,  ) = Potential Difference (volts, V) Current (amps, A) What is the resistance of the following: 1)A bulb with a voltage of 3V and a current of 1A. 2)A resistor with a voltage of 12V and a current of 3A 3)A diode with a voltage of 240V and a current of 40A 4)A thermistor with a current of 0.5A and a voltage of 10V 20  33 44 66

21. 22/11/2016 Wiring a plug Earth wire Neutral wire Insulation Live wire Fuse 1. 2. 3. 4. 5. 6. Cable grip The Earth wire of a plug keeps the device safe by stopping the appliance becoming “live” The neutral wire of a plug is used to complete the circuit.

22. 22/11/2016Fuses 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

23. 22/11/2016 Circuit breakers Residual Current Circuit Breakers (RCCBs) are often used with fuses. They have some advantages over fuses: 1)They are safer – they don’t get hot 2)They react more quickly 3)They can be switched off for repairs 4)They are easy to reset 5)Each RCCB is attached to a certain circuit, so if one switches off you can see which circuit has a fault

24. 22/11/2016 Earth wires 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

25. 22/11/2016 Power and fuses Power is “the rate of doing work”. The amount of power being used in an electrical circuit is given by: P IV 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).

26. 22/11/2016 Power and fuses Copy and complete the following table: AppliancePower rating (W) Voltage (V)Current needed (A) Fuse needed (3, 5 or 13A) Toaster920230 Fire2000230 Hairdryer300230 Hoover1000230 Computer100230 Stereo80230

27. 22/11/2016 Power and fuses Copy and complete the following table: AppliancePower rating (W) Voltage (V)Current needed (A) Fuse needed (3, 5 or 13A) Toaster92023045 Fire20002308.713 Hairdryer3002301.33 Hoover10002304.35 Computer1002300.433 or 1 Stereo802300.33 or 1

28. 22/11/2016 P4d: Ultrasound

29. 22/11/2016 Waves- Some definitions… 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)

30. 22/11/2016 Transverse vs. longitudinal waves Transverse waves are when the displacement is at right angles to the direction of the wave (e.g. light and other electromagnetic waves)… Longitudinal waves are when the displacement is parallel to the direction of the wave (e.g. sound waves)… Displacement Direction Displacement Where are the compressions and rarefactions?

31. 22/11/2016Ultrasound 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 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?

32. 22/11/2016 Other uses of ultrasound 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.

33. 22/11/2016 P4e: What is Radioactivity?

34. 22/11/2016 The structure of the atom ELECTRON – negative, mass nearly nothing PROTON – positive, same mass as neutron (“1”) NEUTRON – neutral, same mass as proton (“1”)

35. 22/11/2016 Introduction to Radioactivity 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)”.

36. 22/11/2016 Types of radiation 1) Alpha (  ) – an atom decays into a new atom and emits an alpha particle (2 protons and 2 ______ – the nucleus of a ______ atom) 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. 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. Unstable nucleus New nucleus Alpha particle Beta particle Gamma radiation Words – frequency, proton, energy, neutrons, helium, beta

37. 22/11/2016 Changes in Mass and Proton Number Alpha decay: Am 241 95 Np 237 93 α 4 2 + 90 39 Sr 90 38 Y β 0 + Beta decay:

38. 22/11/2016Ionisation 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.

39. 22/11/2016 Half life 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… At start there are 16 radioisotopes After 1 half life half have decayed (that’s 8) After 3 half lives another 2 have decayed (14 altogether) After 2 half lives another half have decayed (12 altogether) = radioisotope= new atom formed

40. 22/11/2016 A radioactive decay graph Time Activity (Bq) “1 Becquerel” means “1 radioactive count per second”

41. 22/11/2016 A radioactive decay graph Time Count 1 half life

42. 22/11/2016 P4f: Uses of Radioisotopes

43. 22/11/2016 Background Radiation Radon gas Food Cosmic rays Gamma rays Medical Nuclear power 13% are man-made

44. 22/11/2016 Background Radiation by Location 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

45. 22/11/2016 Uses of radioisotopes - tracers 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.

46. 22/11/2016 Uses of radioactivity – smoke detectors Smoke detectors Alarm +ve electrode -ve electrode Alpha emitter Ionised air particles If smoke enters here a current no longer flows

47. 22/11/2016 Uses of radioactivity – dating rocks 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. 8 8 Answer: The sample was originally completely uranium… …of the sample was uranium 4 8 2 8 1 8 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. 1 half life later…

48. 22/11/2016 An exam question… 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

49. 22/11/2016 Carbon Dating 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

50. 22/11/2016 P4g: Treatment

51. 22/11/2016 X-Rays and Gamma Rays 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.

52. 22/11/2016 Uses of Radioactivity - sterilisation 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.

53. 22/11/2016 Uses of Radioactivity - Treating Cancer 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.

54. 22/11/2016 Uses of radioactivity – medical tracers 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.

55. 22/11/2016 Exposure to Radiation 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).

56. 22/11/2016 P4h: Fission and Fusion

57. 22/11/2016 How Power Stations Work 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

58. 22/11/2016 Nuclear power stations Notice that the heat from these reactions is used to heat water and turn it into steam, which then drives turbines.

59. 22/11/2016 Nuclear fission Uranium or plutonium nucleus Unstable nucleus New nuclei (e.g. barium and krypton) More neutrons Neutron

60. 22/11/2016 Chain reactions 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!!

61. 22/11/2016 Fission in Nuclear power stations 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.

62. 22/11/2016 Nuclear Fusion in stars ProtonNeutron Nuclear fusion happens in stars but it’s not possible to use it in power stations yet as it needs temperatures of around 10,000,000 O C and very high pressures.

63. 22/11/2016 Cold Fusion 22/11/2016 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.