P7 Energy Flashcards
What is magnetic energy store?
Energy stored when like poles are pushed closer together / opposite poles pulled further apart
What is thermal energy store?
Due to vibrations of particles in object - hotter = vibrates faster
What is chemical energy store?
Energy store associated with chemical bonds eg those between molecules
What is kinetic energy store?
Energy associated with a moving object
What is electrostatic energy store?
Energy stored when like charges are moved closer together / opposite charges moved further apart
What is elastic energy store?
Energy stored when an object is stretched, squashed or twisted
What is gravitational energy store?
Energy associated with an object at height
What is nuclear energy store?
Energy associated with nuclear interactions
When a ___ occurs, energy is ___ from one ___ to another
Change
Transferred
Store
What is mechanical energy transfer?
When forces act to cause a change
Eg a car
What is electrical energy transfer?
When an electric current flows in a circuit
Eg a mobile phone
What is thermal energy transfer?
When heat energy is transferred through the motion of particles
Eg a radiator
What is radiative energy transfer?
When electromagnetic waves transfer energy
Eg photosynthesis
What is the law of energy conservation?
The total amount of energy stored in a closed system is constant. It can only be transferred from one form to another
What is efficiency?
A measure of how much input energy is transferred in a useful way
When a ____ acts on an object, there will be a…
We say…
Force
Transfer of energy
Work is done
How can we make mechanical devices more efficient?
Lubrication to reduce friction - reduces wasted energy in the form of thermal
Why are nuclear power stations often located by the coast?
Large volume of water required for cooling
What is specific heat capacity?
The amount of energy needed to raise the temperature of 1kg of a substance by 1 degree
The higher the specific heat capacity…
The more energy the material can hold
The longer it will take to heat up or cool down
Salty water has a ____ specific heat capacity than ____ water
Lower
Fresh
Would it be better to build a nuclear reactor by a fresh water lake or the coast?
Fresh water lake because fresh water has a higher specific heat capacity - will absorb more energy but only raise its temp by a small amount
Define specific latent heat
Energy needed to break intermolecular bonds and cause a change of state of 1kg of a material
What is thermal conductivity?
A property of a material that measures the rate of energy transfer through a material
How do we make a fair test for thermal conductivity?
Area of 1m squared
Thickness of 1m
Temp difference across it of 1 degree
How does insulation slow rate of cooling?
Traps air in foam
Air is poor conductor of heat - slows conduction
What is the rule for current in a series circuit?
Same everywhere
What is the rule for potential difference in a series circuit?
Total pd = sum of pd across components
What is the rule for resistance in series circuits?
Resistors in series increases overall resistance
Add them together
What is the rule for current in parallel circuits?
Split between branches
What is the rule for potential difference in parallel circuits?
Each branch has same pd as power supply
What is the rule for resistance in parallel circuits?
Overall resistance is less than any of the individual resistors
Power = ?
Rate of energy transfer
Efficiency = ?
The percentage of the input energy transferred into useful stores
Dissipation = ?
The transfer of energy to the thermal store of the surroundings
Unit for energy?
Joules
A unit is…
1 kilowatt hour
Define kilowatt hour
A kilowatt hour is the amount of energy transferred by a 1 kilowatt device when switched on for 1 hour
