Conservation And Dissipation Flash Cards
How can the efficiency of boiling water in a pan be improved?
By placing a lid on the pan to reduce the heat loss from the top
State the law of energy conservation
Energy cannot be created or destroyed only transferred into different forms
State any changes in the total energy of a ball 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 waist energy
The energy that is not used by the device for its desired purpose
Describe the energy changes that occur in a filament light bulb
Electric energy is transferred unit light and heat energy.
Light is a useful energy form, heat is waste energy
State two equations to calculate efficiency
Efficiency=useful output energy transfer/total input energy transfer
Efficiency=useful power output/total power outpu
How can efficiency of a system be increased
- reducing waist output (lubricant, thermal insulation)
2. recycling waste output (recycling thermal waste energy as input energy)
State the consequence for energy transfer of a material with a high thermal conductivity
The rate of energy transfer through the material is higher than for a material with a lower thermal conductivity
Do double glazed windows have a higher or lower thermal conductivity than single glazed windows
Lower meaning less energy transfers through them
What key factors effect the rate of cooling of a building
Thickness of the walls
Thermal conductivity of the walls
State three methods of reducing heat loss in a building
Double glazing
Loft and wall insulation
Thicker 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
