4.1.2 P1 Conservation and dissipation of energy (will come up) Flashcards
What happens when energy is dissipated with an example
Some energy is always dissipated when an energy transfer take place
Its also known as wasted energy as the energy gets stored in a way which is not useful
Eg when you charge a phone some energy is dissipated to the thermal energy store
How can you reduce unwanted energy transfers
Insulating objects eg a kettle so less heat goes to surroundings
Lubricating eg an axel for an electric fan
Making objects more streamlined
What happens when the thermal conductivity of a material is high
The higher the thermal conductivity of a material the higher the rate of energy transfer by conduction across the material
How do cavity walls reduce the amount of energy transferred
The air gap in the middle reduces the amount of energy transferred by conduction through the walls because air is an insulator
State the law of energy conservation
Energy cannot be created or destroyed
it can only be 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 waste 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
Electrical energy is transferred into light and heat energy
Light is a useful energy form, heat is waste energy
How can the efficiency of a system be increased
Reducing waste output (by lubrication, thermal insulation)
Recycling waste output
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 lower thermal conductivity
Do double-glazed windows have a higher or lower thermal conductivity than single-glazed windows
Lower as less energy transfers through them
What key factors affect the rate of cooling of a building
The thickness of the walls
Thermal conductivity of the walls
3 methods of reducing heat loss in a building
Double glazing
Loft and wall insulation
Thicker walls
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 be improved
By placing a lid on the pan to reduce the heat loss from the top
