Flashcards
P1
Cards in this deck (86)
- 1What are infrared waves part of?The electromagnetic spectrum.
- 2How can we detect infrared radiation?With our skin-It makes us feel warm.
- 3What do all object do?Emit infrared radiation.
- 4What does it mean if the object is hotter?There is more infrared radiation emitted, in a given time.
- 5What can infrared radiation travel through?A vacuum, as in travelling through space. This is how we get energy from the sun.
- 6What are good absorbers of infrared radiation?Dark, matt surfaces.
- 7What will become hotter in the sun? A object painted dull black, or a object painted shiny white.The dull black object.
- 8What are good emitters of infrared radiation?Dark matt surfaces
- 9What are good reflectors of infrared radiation?Light, shiny surfaces.
- 10What are the three states of matter?Solid, liquid and gas.
- 11How can we make a substance change between states?Melting and cooling.
- 12Why has a sold got a fixed shape?Because the particles vibrate in a fixed positions.
- 13Why doesn't a liquid have a fixed shape?Because the particles are in contact with each other but can move about at random.
- 14Why doesn't a gas have a fixed shape?Because the particles are usually far apart and move at random much faster.
- 15Can a gas flow?Yes. The density of a gas is much less than that of a sold or liquid.
- 16Where does conduction mainly occur?In solids, most liquids and all gases are poor conductors.
- 17How is energy transferred through a solid?The particles at the end that is being heated vibrate more as they gain kinetic energy and this energy is then passed to neighbouring particles.
- 18Where does conduction occur?In metals
- 19Why are metals good conductors?Because when they are heated, their free electrons gain kinetic energy and move through the metal, transferring energy by colliding with other particles.
- 20What are poor conductors?Insulators, materials such as wool and fibre glass are good insulators because they contain trapped air.
- 21Where does convection occur?In fluids. Fluids are liquids and gases.
- 22How is energy transferred throughout a fluid?When a fluid is heated it expands. The fluid become less dense and rises. The warm fluid is replaced by cooler, denser fluid. The resulting convection current transfers energy throughout a fluid.
- 23How are convection currents used on a small and large scale?Small: Such as heating water in a beaker
Large: Such as heating the air above land and sea. Convection current are responsible for onshore and offshore breezes. - 24What is evaporation?Evaporation is when a liquid turns into a gas.
- 25Why does evaporation take place?Because the most energetic liquid molecules escape from the liquids surface and enter the air. Therefore the average kinetic energy of the remaining molecules is less. So the temperature of the liquid decreases. This means that evaporation causes cooling.
- 26How is the rate of evaporation increased?-Increasing the surface are of the liquid.
-Increasing the temperature of the liquid.
-Creating a draught of air across the liquids surface. - 27What is condensation?When a gas turns into a liquid.
- 28Where does condensation often take place?On cold surfaces, such as windows and mirrors.
- 29How is the rate of condensation increased?-Increasing the surface area
-Increasing the surface temperature - 30How is the rate of energy transferred increased?By increasing the temperature difference between an object and its surroundings.
- 31What does the rate at which energy is transferred dependant on?-The material the object is in contact with
-The objects shape
-The objects surface area - 32How do we maximise the rate of energy transfer to keep things cool?We may use things that:
-Are good conductors
-Are painted dull black
-have the air flow around them maximised. - 33How do we minimise the rate of energy transfer (keep things warm)?We need to minimise the transfer of energy by conduction, convection and radiation. We use things that:
- Are good insulators
-Are white and shiny
-Prevent convection currents by trapping air in small pockets. - 34Label a vacuum flask?-A plastic cap
--Double-walled glass (or plastic) container
-Plastic protective cover
-Hot or cold liquid
-Sponge pad (for protection)
-Inside surfaces silvered to stop radiation
-Vacuum prevents conduction and convection
-Plastic spring for support - 35What happens when we heat something?We transfer energy to it which will increase its temperature.
- 36What is the specific heat capacity of a substance?The amount of energy required to raise the temperature of 1 kilogram of the substance by 1 degree Celsius.
- 37What do different substances have?Different heat capacities.
- 38What does having a greater specific heat capacity mean?More energy is required for each degree temperature change. For example the specific heat capacity of aluminium is 900j/kg, and copper is 490j/kg, if we wanted to raise the temperature of 1kg of aluminium, we would need to transfer almost twice the energy needed to raise the temperature of 1kg of copper by the same amount.
- 39Does increasing the mass of a substance, lower of higher the amount of energy required for each degree change?Higher, if we had a 2 kg piece of copper we would need to transfer twice the energy needed to raise the temperature of 1kg of copper by the same amount.
- 40What is the equation for specific heat capacity?E=m x c x 0
E=energy transferred(j)
m=mass (kg)
c=Specific heat capacity (j/kg Celsius)
0 is temperature change (Celsius) - 41How can people minimise the rate of energy transfer out of their homes to reduce fuel bills?- Fibre glass loft insulation to reduce energy transfer by conduction.
-Cavity wall insulation that traps air in small pockets to reduce energy transfer by convection.
-Double glazing to reduce energy transfer by conduction through windows.
-Draught proofing to reduce energy transfer by convection.
-Aluminium foil behind radiators to reflect infrared radiation back into the room. - 42What does the U-Value of a material tell us?How much energy per second passes through it.
- 43What does knowing the U-Values of different materials allow us to do?Compare them, the lower the U-Value the better the material is as an insulator.
- 44How are solar heating panels run?They contain water that is heated by radiation from the sun. This water may then be used to heat buildings or provide domestic hot water.
- 45Why are solar heating panels cheap to run?Because they do not use fuel. However they are expensive to buy and install, and water is not heated at night.
- 46What different forms does energy exist as?Light
Sound
Kinetic
Nuclear
Electrical
Gravitational Potential
Elastic Potential
Chemical - 47What forms of energy are stored?Gravitational Potential
Elastic potential
Chemical - 48Can energy be transferred from one form into another?Yes
- 49What energy does a falling object have?It transfers gravitational Potential energy to kinetic.
- 50What energy does any object above the ground have?Gravitational Potential
- 51Can you create energy?No, you cannot create or destroy energy, only transfer it form one form into another, or from one place to another.
- 52What does the fact that energy cannot be created or destroyed mean?That the total amount of energy is always the same. This is called the conservation of energy and it applies to all energy transfers.
- 53What does stretching an elastic band transfer?Chemical energy to elastic potential energy
- 54In a solar cell, what energy is transferred?Light energy into electrical energy.
- 55What energy does a swinging pendulum transfer?Gravitational potential to kinetic energy and back again as it swings.
- 56What is a machine?Something that transfers energy from one place to another or form one form into another.
- 57What energy do we get out of a machine?Useful energy: Which is transferred to the place we want and in the form we want it.
Wasted Energy:, which is not usually transferred. - 58Where will both the useful and wasted energy be transferred?To its surroundings, and make them warm up. As the energy become more spread out, it becomes more difficult to use for further energy transfers.
- 59Why is energy often wasted?Because of the friction between the moving parts and of a machine. This energy warms the machine and the surroundings.
- 60In what cases may friction be useful?In the brakes of a bicycle of car. Some of the kinetic energy of the vehicle is transferred to energy heating the breaks.
- 61What is energy measure in?Joules. This unit is used for all forms of energy.
- 62What is input energy?The energy supplied to a machine.
- 63From the conservation energy we know what?Input energy=Useful energy transferred+ energy wasted
- 64What make a machine efficient?The less energy wasted.
- 65How do we calculate the efficiency of an appliance?Efficiency=Useful energy transferred by the appliance, divided by total energy supplied to the appliance time by 100%.
- 66How can the efficiency be written?Left as a fraction or multiplied by 100 to give a percentage.
- 67No appliance can be 100% efficient except one what is it?An electric heater, which usually transfers all the electrical energy supplied to it by heating its surroundings.
- 68What can the energy transfer be represented with?A Sankey Diagram
- 69Why are electrical appliances useful?They transfer electrical energy into whatever form of energy we need at the flick of a switch.
- 70Name a few electrical appliances?-Lamps to produce light
-Electric mixers to produce kinetic energy
-Speakers to produce sound energy
-Televisions to produce light and sound energy. - 71How should appliances be designed?Too waste as little energy as possible.
- 72What is the power of an appliance?The rate at which it transfers energy.
- 73What is the unit of power?Watt (W) An appliance with a power of 1 watt transfers 1 joule of electrical energy to other forms of energy every second.
- 74Often a watt is too small a unit to be used. what is used instead?A kilowatt=1000watts
- 75What is the equation for power?P=E/t
P=Power in watts
E=energy in joules
t=time taken in seconds - 76Equation for efficiency in terms of power?Efficiency= Useful power out/Useful power in x 100%
- 77Companies that supply mains electricity charge customers for what?The amount of electrical energy they use.
- 78Because of the large numbers involve with companies Joules are not used what is the amount of energy used measured in?The amount of energy used is measured in Kilowatt-hour(kWh).
- 79What is a kilowatt hour?The amount of energy that is transferred by a one-Kilowatt appliance when used for an hour.
- 80What is the equation used for calculating how much energy is transferred to a mains appliance?E=P x t
E=Energy transferred
P=Power of the appliance is kW
t=Time taken in hours - 81What does an electricity meter in a house record?The number of kWh of energy used. If the previous meter reading is subtracted form the current reading the electrical energy used between the reading can be calculated.
- 82What is the equation for the cost of the electrical energy supplied?Total cost=No. of kWh x Cost per kWh
The cost per kWh is given on the electricity bill. - 83In order to compare the cost effectiveness of different appliances we must consider a number of different cost such as what?-The cost of buying the appliance
-The cost of installing the appliance
-The running costs
-The maintenance costs
-Environmental costs
-The interest charged on a loan to buy the appliance - 84How could householders reduce their energy bill?By buying newer, more efficient appliance such as a new fridge or by installing materials designed to reduce energy wastage such as loft insulation.
- 85What is payback time?The time it takes for an appliance or installation to pay for itself in terms of energy savings.
- 86What are the energy loss percentages in a house?-25% through the roof
-35% through the walls
-15% in draughts
-15% through the floor
-10% through the windows
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- Flashcards on P1, created by Lilian Sandhu on 18/03/2015.
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- Lilian Sandhu
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