energy Flashcards
What is the advantage of transmitting electricity at a very high potential difference?
less thermal energy is transferred to the surroundings
Define the specific heat capacity of a substance
The amount of energy needed to raise the temperature of 1 kg of a substance by 1°C
State the units for specific heat capacity
j/degrees Celsius/kg
what is the definition of power?
The rate of which energy is transferred
Describe the energy changes involved when a ball is thrown upwards and then returns to it starting position
upwards:KE is converted to GOE
peak:maximum GPE,zero KE
downwards:GPE is converted to KE
explain why a bungee jumper slows down once the cord begins to stretch
Kinetic energy decreases since it is converted to a elastic potential
Since kinetic energy is proportional to velocity squared as kinetic energy decreases, so does velocity
give two examples of chemical energy stores
Food fuel batteries
State for different stores of energy
Kinetic energy, gravitation and potential energy, elastic potential energy, chemical energy
State any changes in the total energy of a bar that is kicked, assuming that no external forces act
The total energy of the system remains constant due to the conservation of energy
what is waste energy?
The energy that is not used by the device for its desired purpose
How can the efficiency of a system be increased?
reducing waste output(by lubrication, thermal insulation)
Recycling waste output (recycling thermal waste energy as an input energy)
State the consequence for energy transfer of material with a high thermal conductivity
The rate of energy transfer for the material is higher than material with a lower thermal conductivity
Do double glaze windows have a higher or lower firm or conductivity than single glaze windows?
Low, meaning less energy transfers through them
What key factors affect the rate of cooling of a building?
The thickness of the walls, the thermal conductivity of the walls
How can the efficiency of a mechanical machine with moving parts be improved?
lubricate any moving parts to reduce the friction and therefore energy loss due to heating
how can the efficiency of a radiator be improved?
Installing metal foil sheets behind the radiator to reflect the heat back into the room rather than it being absorbed into the walls
How can the efficiency of boiling water in a pan being improved?
By placing a lid on the pan to reduce the heat loss from the top
what is a renewable energy resource?
An energy source, which can be a replenished as it is been used up
Give four examples of renewable energy resources
Wind, hydroelectricity, tidal ,solar
what are the advantages of generating power using gas rather than coal?
Flexible generation: gas power stations have short start-up time so it can be switched on/off more readily
Lower missions of carbon dioxide
State two disadvantages of using renewable energy resources to generate power
Output often determined by external factors(like wind speed) so supply is uncertain
Generating power through other means is often more efficient and economical beneficial
Explain environmental impacts of burning fossil fuels
carbon dioxide contributes the greenhouse effect and causes global warming
Sulphur dioxide leaves to acid rain which can damage buildings and crops
State three advantages of fossil fuels as energy resource
reliable: not dependent on external factors who can generate power any time
Can produce larger amount of energy for a given quantity
Still relatively abundant, so cost-effective
State three advantages of nuclear power
Very large amounts of energy for relatively small quantities of fuel
Doesn’t release greenhouse gases and so doesn’t contribute to climate change
Low fuel costs
