Physics Flashcards
Energy cannot be… but it can be…
created or destroyed
transferred, stored, or dissipated
Dissipated energy =
waste energy
Give an example of dissipated energy
thermal energy in car
sound energy in blenders
light energy on fire
Higher thermal conductivity =
higher rate of energy transferred by conduction
Should building insulators have a high or low thermal conductivity?
low
With a thicker material, is more or less heat conducted?
less
Kinetic energy (J) =
0.5 x mass (kg) x velocity squared (m/s)
Elastic potential energy (J) =
0.5 x spring constance (N/m) x extension squared (m)
Gravitational potential energy (J) =
mass (kg) x gravitational field strength (N/kg) x height (m)
What should we assume the gravitational field strength is if not stated otherwise?
10N/kg
work done is the same as…
energy transferred
How many energy stores are there?
8
Name all energy stores
(write on whiteboard)
Thermal, kinetic, gravitational potential, elastic potential, chemical, magnetic, electrostatic, nuclear
Name the 4 ways energy is transferred
mechanically (force), electrically (moving charges), heating, or radiation
What is a system?
single object or group of objects
When a system changes, what 3 ways is energy transferred?
into or away from the system, between different objects in the system, and between different types of energy stores
Closed system =
no matter or energy can enter or leave
net change = 0
Radiation = + example
electromagnetic waves at the speed of light
e.g. the sun
Conduction = + example
transfer of heat between adjacent (nearby) molecules
e.g. burning feet on hot sand
Convection = + example
Transfer or heat through the air or liquid currents. Warmer and less dense regions will rise above denser, cooler regions. Therefore heat is transferred from warmer regions to cooler regions.
e.g. boiling water in a kettle
Change in thermal energy (J) =
mass (kg) x specific heat capacity (J/kg degrees) x temperature change (degrees)
Power (W) =
work done (J) divided by time (s)
Work done (J) =
force (N) x distance (m)
Efficiency =
useful energy transfer (J) divided by total energy transferred (J)
What is an insulator?
a material that does not conduct electricity
Name all fossil fuels
coal, oil, and natural gas
What is the difference between renewable and non-renewable resources?
Renewable will never run out, whereas non-renewable will one day.
Name all renewable energy sources
solar, wind, water waves, hydro-electricity, bio-fuel, tides, geothermal
Which type of energy source provides most of our energy?
Non-renewable
Which type of energy source causes more damage to the environment?
Non-renewable
Whenever something moves, what type of force usually acts against it?
Frictional force
What can be used to reduce the friction between the objects’ surfaces when they are rubbed together?
Lubricants
What is an example of a lubricant?
usually liquid (like oil)
When an object is heated, where is the energy transferred to?
thermal energy stores
Name all types of renewable energy sources
(write on whiteboard)
Wind power
Solar cells
Geothermal power
Hydroelectric power
Wave power
Tidal barrages
Biofuels
What does wind power involve doing?
Putting lots of wind turbines up in exposed places like on moors or round coasts.
Each turbine has blades that turn the generator inside and produce electricity.
Positives of wind power
No pollution
No permanent damage to the landscape
Minimal running costs
Negatives of wind power
Spoil the view
Very noisy
Turbines stop when winds stop or wind too stong
High initial costs
Describe how solar cells work
They generate electric currents directly from sunlight
Positives of solar cells
No pollution
Reliable in sunny countries
Running costs minimal
Negatives of solar cells
Only works in daytime
High initial costs
Describe how geothermal power works
Possible in volcanic areas or where hot rocks lie near the surface
The source of energy is the slow decay of various radioactive elements deep inside the earth
Positives of geothermal power
Free
Very little damage to enviroment
Negatives of geothermal power
Not very many suitable locations
Describe how hydroelectric power works
Flooding of valleys by building a big dam. Water is allowed out through turbines.
Positives of hydroelectric power
No pollution
Immediate energy
Minimal running costs
Negatives of hydroelectric power
Big impact on the environment
High initial costs
Describe how wave power works
Lots of wave-powered, moving turbines located around a coast are connected to a generator
Positives of wave power
No pollution
Minimal running costs
Negatives of wave power
Disturbs marine animals
Spoils view
Hazard to boats
High initial costs
Unreliable as when wind drops, waves tend to die out
Describe how tidal barrages work
Big dams built across river estuaries with turbines in. As the tide comes in, it fills up the estuary, and the water is allowed out through turbines at a controlled speed.
How are tides produced?
By the gravitational pull of the sun and the moon.
Positives of tidal barrages
No pollution
Minimal running costs
Negatives of tidal barrages
Prevents free access by boats
Spoils view
Alters habitats of creatures who live in sand
High initial costs
Describe how bio-fuels work and what they are used for.
Created from either plant products or animal dung. They can be solid, liquid or gas and they are burnt to produce electricity to run cars in the same way as fossil fuels.
Positives of bio-fuels
Crops take a short time to grow
Negatives of bio-fuels
Not immediate
Takes up space for other crops that are grown for food
Increases CO2 and methane emissions
What are the different types of non-renewable energy?
Fossil fuels and nuclear energy
Positives of non-renewable energy
Cost-effective
Quick response for change in demand
Negatives of non-renewable energy
Slowly running out
Coal, oil and gas release CO2 into the atmosphere which adds to the greenhouse effect and contributes to global warming
What does cavity wall insulation do?
When houses have cavity walls (inner and outer walls with a gap in the middle) we can fill them with foam. This reduces energy transfer by convection.
What does loft insulation do?
Reduces convection currents being created in lofts
What do double-glazed windows do?
Leave an air gap between two sheets of glass to prevent energy transfer by conduction.
What do cavity walls do?
Leave an air gap between the inner and outer walls which reduces the amount of energy transferred by conduction.
What do draught excluders do?
Block gaps by doors and windows to reduce energy transfer by convection (like in Grandad’s living room)
Describe how to do the specific heat capacity experiment
1) Place the beaker on balance and press zero
2) Add oil to the beaker and record the mass of the oil
3) Place a thermometer and immersion heater into the oil
4) Wrap beaker in insulating foam to reduce energy transfer to surroundings
5) Connect a joulemeter and powerpack to the immersion heater
6) Time for 30 minutes
7) Read the number of joules of energy that passed into the immersion heater
8) Read final temperature of oil
