Energy Flashcards
What happens when a system changes?
There are changes in the way energy is stored
calculation of kinetic energy
kinetic energy (J) = 0.5 x mass (kg) x speed squared (m/s)
the calculation for the gravitational potential energy gained by raising an object above ground level
gravitational potential energy (J) = mass (kg) x gravitational field strength (N/kg) x height (m)
the amount of elastic energy stored in a stretched or compressed spring can be found with the equation:
Ee (J) = 0.5 x spring constant (N/m) x extension ^2 (m)
the equation for power (energy transfer)
energy transferred/ time
equation for power (word done)
work done / time
what is wasted energy caused by?
unwanted energy transfer
How can unwanted transfers be reduced ?
lubrcation- reduces the friction that produces heat
tightening any loose parts - prevents unwanted vibration that wastes energy as sound
thermal insulation - resuces heat loss
What is thermal conductivity?
a measure of how well a material conducts energy when it is heated.
What does the rate of cooling depend on?
the thickness and thermal conductivity of the walls
what is special heat capacity?
the amount of energy required to raise the temperature of one kilogram of the substance by 1 degree celsius
what is internal energy?
the total kinetic and potential energy of all the particles that make up a system
what is the result of doing work on a system
it increases the energy stored in a system
How does heating change the energy in a system
by increasing the energy of the particles within it
as energy increases……
what happens to the state and the temperture
it will either increase the temperature or produce a change of state
the law of conservation of energy is ……
energy cannot be created or destroyed
the higher the thermal conductivity of a material
the higher the rate of energy transfer by conduction across the material.
thin walls with hight thermal conductivity will conduct heat …..
the quickest and the building will cool down rapidly
what are the three ways in which thermal energy can be transferred?
radiation, convection and conduction
when does convection occur?
when particles with a lot of heat energy in a liquid or gas move and take the place of particles with less energy
Heat energy is transferred from ______________________ places by convection
hot to cooler
How is heat energy transferred from homes?
convection, conduction, radiation
convection - cold air can enter the house through gaps in the doors and windows and convection current can transfer heat energy in the loft to the roof tiles
conduction - through the walls, floor, roof and windows.
radiation - through the walls, roof and windows.
materials with low thermal conductivity are _______ insulators
good
what are the several ways in which you can reduce heat loss in homes
- carpets, curtains and draught excluders
- double glazing
- cavity wall insulation
- loft insulation
how does double glazing reduce heat loss through windows?
double glazing has a vacuum in between the two panes of glass which means that there will be no conduction or convection
if double glazing has air, convection is minimised because there is little room for the air to move. Air is a poor conductor so there will be very little heat loss by conduction
how is heat loss reduced through cavity wall insulation and loft insulation?
the insulating material is blown into the gap between the brick and the inside wall.
Insulating materials have low thermal conductivity and so this reduces the heat loss by conduction. The material also prevents air circulating inside the cavity, therefore reducing heat loss by convection.
What is a renewable energy resource?
one that is being (or can be) replenished as it is used.
What are the main uses of energy resources?
transport, electricity generation and heating
What is a non-renewable energy resource?
resources which will eventually run out
what are the renewable energy resources? (7)
bio-fuel wind hydro-electricity geothermal Tidal Solar water waves.
What are the non-renewable energy resources? (4)
- Nuclear fuel
- coal
- oil
- gas
