P5. Energy and Power Flashcards
What is energy?
A number in joules that tells you what is possible but doesnt tell you what will happen
What is an energy store?
A store indicates amount of energy in joules
What are the different types of stores? 6
Chemical
Thermal
Kinetic
Gravitational
Nuclear
Elastic
What is an example of a chemical store?
Coal and oxygen, glucose and oxygen
What is an example of a thermal store?
Hot bath
What is an example of a kenetic store?
Moving car
What is an example of a gravitational store?
Skier at top of hill
What is an example of a nuclear store?
Hydrogen in sun
What is an example of an electrostatic store?
Stretched elastic band
What is an example of a magnetic store?
Opposite poles of magnet held apart
What are the 4 ways energy is transferred?
Mechanical
Heated by radiation
Electrical
Heated by particles
What is the conservation of energy?
Energy cannot be created nor destroyed, energy can only be transferred between stores
How do you do an energy analysis?
Choose two points in a process
Identify which stores have more or less energy in them at those points
Work out which type of transfer has transferred the energy between stores
How do you know which energy transfer it is?
Mechanical is most things
Electrically - electrical current
Rest are self explanatory
When is energy transferred in an electric current?
When a charge is moved.
In electrical devices, energy is transferred when a charge moves from…? (2)
From chemical potential energy store in battery.
From chemical or nuclear store in a power station
What do electrical appliances transfer electrical energy from?
Chemical potential store
What affects the cost of electricity? 2
Power
Time
What is power?
Power is energy transferred every second?
What is the unit of power?
Watts
What is energy dissipation?
You cannot use the energy in the surroundings, it has been dissipated and is no longer in a store that is useful
What is lubrication?
You can reduce energy dissipated due to friction by lubrication
What is insulation?
You can reduce the energy dissipated due to heating by insulation
What is an insulator?
Material that doesnt conduct very well between hot and cold object
True or False: Using lubrication or insulation reduces energy transferred to thermal store of surroundings?
True
What does the rate at which energy is transferred through walls depend on? 3
Thickness of the wall
What they are made of
Difference in temperature between two sides of the wall
What is efficiency?
How good a device is at converting energy into useful forms of energy known as its efficiency
What do you need to think about when building walls? Efficiency
Thermal conductivity of the material
What is thermal conductivity?
How quickly energy is transferred through a wall with:
an area of 1m^2
a thickness of 1m
a temperature difference across it of 1 degree celsius
What is better for staying warm? Low or high thermal conductivity?
Low
Why can igloos stay warm?
Ice has a low thermal conductivity
if you want to increase efficiency, what do you need to reduce? ( not examples)
You need to reduce wasted energy
How do you reduce the wasted energy?
Use Insulation to reduce heating of surroundings
Use technology that are better at their job
