2695862
Descrição
FlashCards por Charlie Murray, atualizado more than 1 year ago
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Criado por Charlie Murray
mais de 9 anos atrás
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| Questão | Responda |
| Difference between ac and dc | AC = Alternating current. Current constantly changes direction. DC = Direct current. Current flows in one direction only. |
| Mains frequency and Mains voltage | 50Hz and 230V |
| What are plugs made of? What are wires made of? What are pins made of? | Plastic (good electrical insulator, prevents anyone touching it from receiving an electric shock) Copper (good electrical conductor, bends easily) Brass (good conductor, doesn't rust/oxidise) |
| Diagram of a Plug | bLue = Left bRown = Right sTriped = Top |
| How to determine the frequency of an a.c. supply | 1 __________ time taken for 1 cycle |
| How do fuses work? How does an RCCB work? | Contains a thin wire that will melt if current through them is too high. (should always be in series with live wire between live wire and appliance. When fuse blows, appliance is cut off from live wire." Electromagnet switch that switches a circuit off by detecting a difference between current in live and neutral wires. |
| Comparison of RCCB and Fuse | RCCB can switch a current off faster. Safer. RCCB can be reset, whereas a fuse will simply melt when a high current flows through it. |
| Why do appliances with plastic cases not need earthing? | Plastic is an insulator so cannot become live. |
| How Earth wire protects user | If fault occurs and connects live wire to case Earth wire carries current from case back down Earth wire. Big current flows and melts fuse. |
| What is an isotope? | An element with the same proton number but a different neutron number. |
| Natural Sources of Background Radiation | Cosmic rays Rock e.g. granite Food and drink |
| Artificial Sources of Background Radiation | Nuclear weapons testing X-rays Medical scanners |
| Nature of alpha radiation Nature of beta radiation Nature of gamma radiation | 2 protons and 2 neutrons (same as helium nucleus) Electron Electromagnetic radiation |
| Charge of alpha radiation Charge of beta radiation Charge of gamma radiation | +2 -1 0 |
| fastest type of radiation | Gamma, then beta, then alpha |
| Most penetrating type of radiation? | Gamma, then beta, then alpha |
| Which type of radiation is the most ionising? | Alpha, then beta, then gamma |
| Uses of radiation | Alpha: Smoke alarms Controlling paper thickness Beta: Controlling foil thickness Gamma: Medical tracers Sterilise surgical equipment Kill cancer cells (radiotherapy) |
| Plum pudding model of nucleus and why it was rejected | No nucleus Mass is spread out +ve charge spread out Embedded electrons Couldn't explain why some alpha particles were scattered through large angles. |
| Nuclear model of nucleus and why it was accepted. | There's a nucleus where the charge and mass are concentrated. Electrons orbit nucleus. Correctly explained why, in Geiger and Marsden's experiment, some alpha particles were scattered through large angles. Explains radioactivity in terms of changes that happen to an unstable nucleus when it emits radiation. Predicted existence of neutron, which was later discovered. |
| What happens in alpha particle emission? | Nucleus emits an alpha particle and forms a new nucleus. |
| What happens in beta particle emission? | A neutron in the nucleus changes into a proton. A beta particle is created in the nucleus and instantly emitted. |
| What is a half-life? | The time it takes for half the radioactive nuclei to decay |
| What is nuclear fission? Where does it occur and with which substances? | The splitting up of a nucleus into 2 approximately equal fragments, releasing 2 or more neutrons. Occurs in nuclear power stations with uranium-235 and plutonium-239 |
| What is nuclear fusion? Where does it occur? | The joining together of light nuclei (e.g. hydrogen) to create heavier nuclei, which gives out a lot of energy. Occurs in stars. |
| What happens in a nuclear reactor? | Core contains nuclear fuel rods made of uranium-235 or plutonium-239 Generates heat. Water is heated and turns to steam. Steam goes through heat exchanger. Heats more, water, which turns into steam, which turns turbines to generate electricity. |
| What to do if a fuse blows/RCCB trips when a mains appliance is in use | Switch appliance off and don't use until it's been checked by a qualified electrician. |
| What to do if an appliance overheats and/or you get a distinctive burning smell from it | Switch it off, don't use it until it's been checked by a qualified electrician |
| What is radon gas and why is is dangerous? | An alpha-emitting isotope that seeps into houses through the ground. |
| How do people who work in jobs involving the use of ionising radiation stay safe? | Wear personal radiation monitors to ensure they're not exposed to too much ionising radiation. |
| Dangers of Radiation | Alpha particles are highly ionising and can cause cancer. (not very penetrating so damage cells unless it gets into the body) Beta and gamma are more penetrating so can get through your skin |
| In deflection, why is an alpha particle deflected much less than a beta particle? | Its mass is about 8000 times that of a beta particle |
| What is ionisation? | When radiation can knock electrons out of atoms, the atoms become charged because they lose electrons. |
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