Flashcards
Keeping homes warm - P1
Cards in this deck (25)
- 1What are conductors?Materials that allow heat energy to spread through them quickly are called conductors.
- 2What are insulators? Which materials are the best insulators?Materials that allow heat energy to spread through them slowly are called insulators. Most non-metals, such as wood, plastic, glass and air, are good insulators.
- 3Give some examples of a good conductor and insulator.A saucepan is made of a good conductor to get the heat to the food, e.g. copper or aluminium.
A saucepan handle is made of a good insulator to stop the heat getting to your hand, e.g. wood or plastic.
Clothing and bedding are both good insulators, because they trap air within their material, and between the layers to stop heat leaving your body.
Curtains are good insulators because they trap a layer of air between them and the window, which helps to reduce heat energy loss by conduction. - 4What is a convection current? Use an example of a radiator to help explain it.When air next to a radiator in a room gets warm it will expand and become less dense, so it will rise up and cooler air will move in to take its place. So hot air rises and warms up the air already at ceiling level. This movement of air is called a convection current.
- 5How can heat move?By convection currents and infrared radiation (a type of electromagnetic wave).
- 6What can infrared radiation be reflected by and absorbed by? Give an example of where the shiny surface is used and why.It can be reflected from shiny surfaces but is very easily absorbed by dark or rough surfaces. This is why putting a shiny surface behind a hot object will reflect the heat, but a dark surface will get very hot.
- 7Why are objects hot?If an object is heated, its particles will start to move more quickly - so a hotter object has faster moving particles . In a solid the particles move by vibrating. In a liquid and gas the particles move around, flowing past each other and moving further apart - which is why hot air is less dense and rises.
- 8Give some examples of heat transfer.A hot-water tank is made of stainless steel, which reduces heat loss by radiation.
Hot water tanks usually have an insulating jacket made of foam to reduce heat loss by conduction and convection.
Refrigerators are insulated to reduce heat gain by conduction and convection. - 9What is an important thing to think about when trying to reduce heat loss in the home?It is important to think about the payback time - how long it takes to pay for the insulation from the savings you make.
- 10Where abouts do houses lose energy through?They lose energy through the doors, windows, floors, walls and roofs. Energy is lost from a source to a sink, so when heat is lost from the home, the home is the source and the atmosphere is the sink.
- 11What does fibreglass loft insulation reduce and how?It reduces conduction and convection, by trapping layers of air (a good insulator) between the fibres.
- 12What does reflective foil on walls behind radiators reduce and how?It reduces radiation, by reflecting infrared heat energy into the room.
- 13What does cavity wall insulation reduce and how?It reduces conduction and convection, by trapping air (a good insulator) in the foam.
- 14What does double glazing reduce and how?It reduces conduction and convection, by trapping air (a good insulator) between the panes of glass.
- 15What does draught excluders reduce and how?It reduces convection, by keeping as much warm air inside as possible.
- 16What are other energy-saving strategies?They include: Drawing the curtains early in the evening to reduce heat loss by convection. Having carpets and sealed floors to stop heat loss through the floor. Keeping inside doors to conservatories closed in cold weather.
- 17What is energy efficiency a measure of?It is a measure of how good an appliance is at converting input energy (the energy supplied) into useful output energy.
- 18Use the television for an example of input and output energy.For a television, the input energy is electrical energy and the useful energy output is light and sound. But TV's also produce heat energy which, in this case, is wasted energy.
- 19What do sankey diagrams show?They show how much energy is transferred and where it is lost.
- 20What is conduction and how does it work?It is the transfer of heat energy through a substance from a hotter region to a cooler region without any movement of the substance itself. As a substance, (e.g. a metal poker for a fire) is heated, the kinetic energy of its particles increases (they vibrate/oscillate more). This kinetic energy is transferred along the poker and, gradually, energy is transferred along it.
- 21Heat energy is transferred by the free electrons in a metal, how does this work?The free electrons flow, collide with and transfer energy to other atoms, increasing their kinetic energy and so the temperature rises. This is why metals are good conductors.
- 22Insulation only stops heat loss by .......?Conduction. Heat energy can still be lost from a hot object by radiation and/or convection. A cavity wall in a house should be filled with foam to trap air and to prevent heat loss by convection and conduction.
- 23What is convection?Because fluids (liquids) and gases can flow, they can transfer heat energy from hotter to cooler regions by their own movement. As the liquid or gas gets hotter, its particles move faster causing it to expand and become less dense. It will rise up and be replaced by colder, denser liquid or gas.
- 24What is radiation?It is the transfer of heat energy by electromagnetic waves. Hot objects emit mainly infrared radiation, which can pass through a vacuum, i.e. no material is needed for its transfer.
- 25How much infrared radiation is given out or taken in by an object depends on its surface. What are these surfaces and what do they do?Dark matt surfaces emit more radiation than pale shiny surfaces at the same temperature.
Dark matt surfaces are better absorbers (poor reflectors) of radiation than pale shiny surfaces at the same temperature.
Information
- Description
- GCSE Physics (P1) Flashcards on Keeping homes warm - P1, created by Rebecca Smith on 26/10/2016.
- Created by
- Rebecca Smith
- Views
- 0
- Rating
More on Thermal Insulation and Heating Buildings