Mechanically (forces), electrically, heating by particles, heating by radiation
9 of 32
Energy transferred mechanically=
(work done) distance*force
10 of 32
Energy transferred electrically=
electrical power*time
11 of 32
Change in thermal energy=
mass*shc*change in temp
12 of 32
What is the Law of conservation of energy?
energy can be stored, transferred between stores and dissipated- but it can never be created or destroyed. The total energy of a closed system has no net change
13 of 32
What happens when energy is trnasferred?
Some energy is always wasted, dissipated
14 of 32
efficiency=
(useful energy output)/(total energy input)
15 of 32
Is any energy tranfer 100% efficient?
No
16 of 32
How can you reduce heat transfer to surroundings?
Using insulation. Lubrication to reduce friction. Use technology better at their jobs (LEDs) create devices from materials that reduce unwanted energy transfer.
17 of 32
power=
current*p.d
18 of 32
power=
energy/time
19 of 32
electrcial energy=
power*time
20 of 32
kWh=
kW*h
21 of 32
What is a kilowatt hour?
Amount of energy transferred by a device with a power rating of 1kW in one hour
22 of 32
What do you pay for electricity in?
kWh
23 of 32
cost=
energy*cost per unit
24 of 32
How is electrical energy generated?
In a power station (usually chemical energy)
25 of 32
How is energy transferred to an electrical device?
Using an electrical pathway
26 of 32
energy in=
energy out
27 of 32
What do we assume when calculating energy tansfers?
All energy goes into useful stores.
28 of 32
What causes energy transfer by heating?
ENergy trnasfers from chemical to thermal store by heating when a fuel burns. An leectrical current can transfer energy to a thermal store (kettle). Energy is transferrend from hotter object to a cooler object by heating
29 of 32
What are 2 factors effecting heat transfers from homes?
Thickness of walls. Thermal conductivity of materail walls are made from.
30 of 32
What does thermal conductivity tell you?
Rate of energy transfer through a material where there is 1m^2 of surface, 1m thick, 1C temp difference
Comments
No comments have yet been made