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What is thermal radiation?
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Which objects emit thermal radiation?
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GCSE Physics P1
| Question | Answer |
|---|---|
| What is thermal radiation? | Energy transfer by electromagnetic waves. |
| Which objects emit thermal radiation? | All objects. |
| What is the relation between the hotness of an object and thermal radiation emitted? | The hotter the object, the more thermal radiation emitted. |
| Which is better at emitting thermal radiation. A dark matt surface, or a shiny, light surface? | Dark matt surface. |
| Which is better at absorbing thermal radiation. A dark matt surface, or a shiny, light surface? | Dark matt surface. |
| How does conduction occur in a metal? | Free electrons transferring energy. |
| Why are non metals poor conductors? | They do not contain free electrons. |
| Why are materials such as fibreglass good insulators? | They contain pockets of trapped air. |
| In which states of matter does convection occur? | Fluids (Liquids and Gases) |
| How does heating a fluid affect density? | Makes it less dense. |
| What causes convection? | A hot liquid or gas rising. |
| Why does a radiator have a large surface area? | So it can lose heat easily. |
| Which loses heat more easily. Small or Large objects? | Small objects. |
| How can heat loss from a building be reduced? | -Aluminium foil behind radiators.-Cavity wall insulation.-Double glazing.-Loft insulation. |
| Does energy only exist in one form? | No, energy exists in many forms. |
| Can energy transform into different forms? | Yes- energy can transfor from one form to another. |
| What is 'The Conservation of Energy'? | Energy cannot be created or desroyed. |
| Can energy be transferred from one place to another? | Yes. |
| What is 'useful energy'? | Energy in the place and form we need it. |
| What is 'wasted energy'? | Not useful energy. |
| What happens to both useful and wasted energy? | Transferred to surroundings as heat. |
| What happens as energy spreads out? | It gets more and more difficuly to use for more energy transfers. |
| What unit is energy measured in? | Joules. |
| How do you calculate the efficiency of a device? | Useful energy (divided by) Total Energy |
| What effect does wasted energy have on efficiency? | Causes inefficiency. |
| What is electrical energy? | Energy transfer due to an electric current. |
| What are electrical devices used for? | Heating, lighting, motorising, sound and visual. |
| What is the unit of power? | Watt (W) |
| What does the unit 'Watt' mean. | 1 Joule / Second |
| What is the calculation to find power? | energy transferred (J) (divided by) time taken (seconds) |
| What is the calculation for energy transferred? (kWh) | power (kW) x time (hours) |
| What is the calculation for price of energy transferred? | number of KWh x cost per kWh |
| What is the national grid? | A network of cables and transformers. |
| What are step up transformers used for in the national grid? | To increase voltage levels from those used in powerstations, to those on the grid. |
| What are step up transformers used for in the national grid? | To decrease voltage levels for use in homes. |
| Why is electricity transferred over the grid at high voltage? | A higher voltage means less current, which means less energy lost as heat. |
| What are generators driven by in power stations? | Turbines. |
| Which releases more energy per kilogram. Uranium or other fossil fuels? | Uranium. |
| What is a wind tubine? | An electricity generator on top of a tall tower. |
| What is a wave generator? | A generator turned by the waves. |
| How are hydrolectricity generators turned? | Water flowing downhill. |
| How does a tidal power station work? | Traps each high tide and uses it to turn generators. |
| How can we use solar energy in the home? | -Solar cells-Solar panels - used to heat water |
| Where does geothermal energy come from? | Radioactive energy from sustances in the earth. |
| What do all fossil fuels produce? | Greenhouse gases. |
| What do all Nuclear fuels produce? | Radioactive waste. |
| What is a disadvantage of using renewable energy sources? | Could affect plant and animal life. |
| List the electromagnetic spectrum in order of increasing wavelength. | Gamma, X, U-V, Visible, Infra red, Microwaves, Radio. |
| At what speed do all electromagnetic waves travel through space? | 300 Million m/s |
| What is the formula for wave speed? | wavelength x frequency |
| What can absorb X-rays and gamma radiation? | Dense materials (eg metal + bone) |
| Are there any disadvantages to humans regarding X rays and gamma radiation? | Damage living tissue when they pass through it. |
| What are X-Rays used for? | In hospitals to take radiographs. |
| What are Gamma rays used for? | Kill bacteria in food, sterilise surgical equipment, kill cancer cells. |
| What are the effects of U-V radiation on humans? | Harms skin and eyes. |
| How can we change the use of radio waves? | By altering the frequency. |
| Which parts of the electromagnetic spectrum are used in fibre optics? | Infra red and visible. |
| Are analogue signals constant in amplitude? | No, they vary. |
| How many form of digital signal are there? | 2 - (1 or 0) |
| WHat are the differences between analogue and digital transmission? | Digital can carry more information and is free of noise and distortion. |
| What does a radioactive substance contain? | Unstable nuclei. |
| How does an unstable electron become stable? | By emitting radiation. |
| How many types of radiation are there? | 3- Alpha beta gamma |
| Can we predict or influence radioactive decay? | No- it is a random event. |
| What is alpha radiation stopped by? | paper or a few cm of air |
| What is beta radiation stopped by? | thin metal or a metre of air |
| What is gamma radiation stopped by? | thick lead, unlimited in air |
| What is the 'half life' of a radioactive isotope? | The time it takes for the number of nuclei of the isotope in a sample halves. |
| What happens to the number of unstable atoms and activity in one half life? | Decreases to half. |
| What affects the use we can make of a radioactive substance? | Half Life, Type of radiation |
| What happens to light from distant galaxies? | It is red-shifted to longer wavelengths. |
| How far away are the most distant galaxies? | 13,000 million light years. |
| Is the universe expanding? | Yes. |
| How didthe universe begin? | The big bang- a massive explosion from a very small point. |
| What is background microwave radiation? | Radiation created just after the big bang. |
| Which electromagnetic waves are absorbed by the atmosphere? | All but visible, radio and some UV. |
| What are satellite detectors used for? | To make observations outside the visible and radio spectrum. |
| What are the advantages of a space telescope? | Less atmospheric distortion, clearer image. |
| What are 2 sources of energy that can respond to surges in demnd for electricity? | Hydroelectric, Tidal. |
| How does convection occur? | Waater molucules gsin kinetic energy and move apart causing the region of water above the flame to expand and rise, carrying the heat with it. |
| Is nuclear a renewable energy source? | No. |
| Are digital signals faster than analogue? | No. |
| Is alpha radiation affected by a magnetic field? | Yes, it is deflected to the negative. |
| Is beta radiation affected by a magnetic field? | Yes, it is deflected to the negative. (opposite to alpha) |
| Is gamma radiation affected by a magnetic field? | No it is not. |
| What is alpha radiation? | Helium Nucleus (2 protons 2 neutrons) |
| What is beta radiation? | A high speed electron from the nucleus. Emitted when a neutron changes to a proton and an electron. The proton remains in the nucleus. |
| What is gamma radiation? | Very short wavelength electromagnetic wave from nucleus. |
| What affects rate of heat transfer? | Shape/dimensions, Temperature difference between body and surroundings. |
| What are the disadvantages of using fossil fuels? | Expensive to build, release greenhouse gases, radioactive waste etc. |
Created by:
james1234190
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