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Description
Flashcards by harv.hill01, updated more than 1 year ago
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Created by harv.hill01
over 8 years ago
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| Question | Answer |
| Generating static electricity | 1. When an insulating material is rubbed with another insulating material 2. Electrons transferred from one material to the other 3. one material has positive charge, another negative (called ions) 4. e.g. dusting brushes, synthetic clothing and balloons on jumper |
| Discharging static electricity | 1. Earth it - electrons transferred from charged object to Easrth 2. Electrostatic shock if you become charged then earthed 3. e.g. friction between carpet and soles of feet, shock when touching radiator |
| Problems of static electricity | 1. Dust attracted to tv screen (insulating) 2. some materials cling to skin 3. discharge of static in flour mill leads to explosion 4. lightning flowing through body |
| repulsion and attraction | 1. Two insulating materials with the same charge repel 2. Two insulating materials with different charges oppose e.g. ebonite and perspex attracted |
| Charging up objects | 1. material receives electrons becomes negatively charged 2. Material that gives away electrons becomes positively charged 3. e.g. perspex rubbed with cloth - positive ebonite rubbed with fur - negative |
| Reducing the danger | 1. correctly earthing appliances 2. using insulation mats effectively 3. wearing shoes with insulating soles 4. e.g. lorries containing flammable substance need to be earthed before unloading anti-static sprays stop charge in first place |
| Using static in everyday life part I | 1. Paint - paint gains electrons as it passes through nozzle (negative) so repel each other forming fine spray, car panel lost electrons (positive), paint sticks so charges cancel = even coat of paint. Less is wasted and even parts in shadow of spray receive a coat |
| Using static in everyday life part II | 2. Smoke precipitors - remove dust particles from chimney. metal grids - high potential difference dust passes, loses electrons giving positive charge, dust particles attracted to negative metal plates, gather there then falll back down |
| Using static in everyday life part III | 3. Defibrillators - two charged paddles in good electrical contact with patients chest with gel are charged, avoiginig chocking the operator |
| Circuits | 1. Electrons flow from negative electrode to positive electrode. |
| Fixed and variable resistors | 1. fixed resistor - constant resistance 2. Variable resistor (rheostat) - changeable resistance. i.e long wire = high resistance, low current. vice versa |
| Current, voltage and resistance | Resistance (Ω) = Voltage (V)/ Current (A) |
| Live, Neutral and Earth wires | 1. Live wire (brown) - carries current to appliance at high voltage (230V) 2. Neutral wire (blue) - completes circuit and carries current away from appliance 3. Earth wire (green + yellow) - safety wire, stops appliance becoming live |
| Double insulation | 1. Appliances with outer metal (conducting) cases are earthed with earth wires. 2. Appliances with insulating cases i.e plastic don't have an earth wire as they're double insulated |
| Earthing | 1. Fault means case becomes live 2. circuit short circuits (flow of charge changes) as earth wire is less resistant 3. fuse wire melts 4. circuit is broken 5. user and appliance protected |
| Fuses and circuit breakers | 1. fault causes current of appliance to exceed rating of fuse 2. fuse wire gets hot and melts 3. circuit broken so current can't flow 4. appliance and user protected circuit breaker - same but can be reset |
| Power | Power (W) = Current (A) x Voltage (V) |
| Example of a fuse in action | 1. current of appliance below current rating of fuse 2. fault mean live wire contacts neutral, so current is higher than fuse rating as less resistance 3. fuse wire gets hotter and melts prevent injury, fire, death and damage |
| Ultrasound p.s - think slinky! | longitudinal waves - above 20.000 Hz 1. rarefaction - area of low pressure 2. compression - area of high pressure 3. wavelength - distance between 2 corresponding points on 2 successive disturbances 4. frequency - waves produced in 1 sec amplitude - max disturbance by wave |
| Applications of ultrasound | Medicine - 1. scanning organs 2. vibrate kidney stones, which break and come out in urine 3. measure speed of blood flow 4. detect gallstones and tumours 5. pre natal scanning as less risk than x-ray |
| More on ultrasound | 1. partially reflected at boundaries - time taken to reflect can be calculated for depth of reflecting surface 2. advantages over X-rays include: a) able to produce image of soft tissue b) doesn't damage living cells |
| Particle motion in waves | |
| Radioactivity | - give out nuclear radiation from nuclei - unstable and decay naturally - during decay, radiation given out as a) alpha - helium nucleus - highly ionising (2+ charge) attracts electrons from atoms b) beta - fast moving electron c) gamma - electromagnetic wave |
| Alpha emission | 1 - atom decays by ejecting alpha particle from nucleus 2. new atom's nucleus differs i.e a) different element b) 2 fewer protons and 2 fewer neutrons c) atomic mass decreased by 2 d) mass number increased by 4 |
| Beta emission | 1 - atom decays by changing neutron into a proton + electron. high energy electron ejected from nucleus is beta particle 2. new atom's nucleus differs i.e a) one more proton, one less neutron b) atomic number increased by one c) muss number stays same |
| Half-life | Igneous rocks can contain uranium atoms which deacy to produce stable lead atoms Rocks can be dated by - 1. measuring proportion of uranium and lead 2. knowing half - life of uranium |
| calculations involving half-life | hello my name is harvey and you smelel tveyhfe |
| background radiation | released by - 1. radioactive substances in soil and rocks 2. comsic rays from outer space 3. Industry and hospitals |
| Tracers | Made of radioisotopes. In industry - 1. track waste dispersal 2. find leaks and blockages in pipes 3. find underground pipe routes leak - material will escape and be detected blockage - material will stop flowing |
| S | Contain alpha emitter which cause air particles to ionise which are attracted to opposite charged electrodes to make an electric current when smoke enters space between electrodes - alpha particles absorbed by smoke - less ionisation occurs - smaller current, alarm sounds |
| Carbon dating | 1. Same amount of carbon 14 in atmosphere 2. dead organism decays and radioactivity decreases 3. ratio between dead and living organism's radioactivity can be used to find approximate age (within 50 years) |
| R | 1. X rays - electromagnetic wave - used in medicine - made by firing high speed electrons at metal target 2. Gamma rays - used in medicine - damage cells, treat cancer - sterilise medical equipment, tracers gamma radiation emitted as extra energy from nucleus post Alpha/beta decay |
| Treating cancer | wide gamma ray beam focused on tumour 2. beam rotated around tumour outside body, to concentrate rays on tumour with less damage to body 3. Destroys cancer without surgery but damage healthy cells and cause sickness |
| Tracers | small half life so patients aren't damaged injected or swallowed by patient spreading monitered by gamma camera e.g. iodine tracer for thryoid gland |
| Producing electricity | 1. conventional - fossil fuels - heat - steam - turbine - generator - electricity 2. nuclear - uranium - reaction - heat - steam - turbine - generator - electricity |
| Fission | 1. Uranium nucleus absorbs extra neutron 2. Nucleus splits releasing energy + neutrons 3. The cycle continues = chain reaction produce radioactive waste nuclear bomb is an uncontrollable chain reaction |
| Fusion | Nuclei fuse together releasing heat energy |
| Small scale nuclear fission | uranium hit with neutron nucleus splits into two smaller nuclei energy and new neutrons released new atoms formed |
| large scale nuclear Fission | control rods placed in reactor, which absorb some neutrons |
| Nuclear Fusion | happens at extremely high temperatures, two nuclei fuse. e.g. hydrogen + hyrdogen = helium in fusion bomb, initial high temperatures needed are produced by fission reaction |
| cold fusion | 1989 - pons and fleischmann claimed to have been able to initiate a fusion reaction at room temperature. However, in 20 years the results they found have not been recipricated |
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