1a) Energy Flashcards
What does radiation depend on?
Surface colour - dark absorb and emit more, light reflects
Texture - Matt absorb and emit more, shiny reflect
In what three ways can heat be transferred?
Radiation (infrared radiation)
Conduction (through solids)
Convection (through liquids and gases)
Define conduction of heat energy
Process where vibrating particles pass on their extra kinetic energy to neighbouring particles
Define convection of heat
More energetic particles move from the hotter region to a colder region and take their heat energy with them
Due to changes in density
Why would the rate of evaporation be faster?
Temp is higher
Density is lower
Surface area is larger
Airflow over liquid is greater (so concentration of air is lower)
Why would the rate of condensation be faster?
Temp of gas is lower
Temp of surface touching the gas is lower
Density is higher
Airflow is less (higher concentration of air)
How to work out payback time of a method of insulation?
Payback time = initial cost/ annual saving
What is specific heat capacity?
Amount of energy needed to raise the temperature of 1kg of a substance by 1oC
How much energy a substance can store
What is the specific heat capacity of water?
4200J/KgoC
What is the law of conservation of energy?
Energy can be transferred usefully from one form to another, stored or dissipated
But it can NEVER be created or destroyed
Formula for efficiency of energy
Efficiency = useful energy out / total energy in
OR
Efficiency = useful power out / total power in
Give an example of an exception to the rule that ‘no device is 100% efficient’
Electric heaters - 100% efficient
All electricity is ultimately usefully converted to heat energy
What are the nine types of energy?
Heat/ Thermal, Electrical, Light, Chemical, Elastic Potential, Sound, Gravitational potential, Nuclear, Kinetic/movement
What is kilowatt hour?
Units of electrical energy
Amount of electrical energy used by 1KW appliance left on for 1 hour
How to work it the no.of units (kwh) used?
No. Of units used = power x time
kwh) (Kw) (Hours
Work out the cost of electricity
Cost = no. of units x price per unit
Disadvantages and advantages of battery radios and clockwork radios
Battery radios - expensive, need replacing, can run out, use harmful chemicals to make them
Clockwork - free, winding needed every few hours to recharge (inconvenient), good for the environment
Describe the particle arrangement of each state
Solid - regular arrangement, fixed position, strong forces of attraction, hold particles close together
Liquids - weaker attraction forces, close together, can move past each other, irregular arrangements
Gases - almost no attraction forces, free to move about, spaced out
Describe the particle energies of each state
Solid - not much energy, can only vibrate in fixed positions
Liquid - more energy than solid particles, move in random directions at low speeds
Gases - more energy than solid and liquid particles, free to move in random directions at high speeds
Why is conduction more efficient through a short fat rod than a long thin one?
The electrons have a shorter path to travel through so heat is passed through quicker
How do solar panels work?
Contain water pipes under a black surface
Radiation from sun absorbed by black surface to heat water in pipes
Water can be pumped to radiators to heat the building
