Energy Flashcards
What is kinetic energy
Energy stored in movin objects
How to calculate kinetic energy?
1/2m X m X v(2)
0.5 X mass (kg) X velocity squared (m/s)
What is specific heat capacity?
amount of energy needed to raise the temperature of 1kg of the substance by 1 C
Formula for energy with SHC
E = mc△t
change in thermal energy (J) - mass (kg) X change in temp (C) X SHC
What is elastic potential energy?
Putting energy to stretch spring, stretched spring is storing this energy called EPE
R/s between force applied and extension(m)
Straight line, directly proportional
If force if too great, it reaches limit of proportionality - inelastically deformed
Formula for elastic potential energy
E = 1/2 X k X e(2)
E = spring constant X extension (m)
Law of conservation of energy
Energy can be transferred usefully, stores or dissipated, but cant be created or destroyed
What is a system
Object/group of objects
What is a closed system
no energ ycan enter/leave
What is dissipated energy?
wasted
How can you reduce dissipated energy?
Reduce friction by:
* Lubricant eg oil
* remove air particles
What is gravitational potential energy
- energy stored in object due to its position above the earths surface
- due to gravity acting on object
Formula for gravitational energy
E = mgh
mass X gr/ field strength X height (m)
When is work done?
when energy is transferred from one store to another
What is mechanical work?
force to move an object
What is electrical work?
current transferring energy
Equation for work done
W = FD
Force (N) X distance (m)
Factors that affect how quickly a building cools down
- Thermal conductivity of walls - the higher TC of material, the higher than rate of energy ransfer by conduction
- Thick walls - reduces rate of thermal energy transfer
What are modern houses built of? How is it kept warm?
- 2 layers: external brick and internal breezeblock
- between there is a cavity
- builders pack cavity with insulating material with low TC
Single glazed vs double glazed
- single = high TC
- double = Low TC
What is loft insulation
- for roof
- low TC reduces thermal energy leaving
What is power?
Rate at which energy is transferred
Formula for power
P = E/T(s)
What is 1 watt
energy transfer of 1j per second
RP: SHC of a liquid
- Place beaker on balance + press 0
- Add liquid and record mass
- Place thermometer and immersion heater in liquid
- Read starting temp of liquid
- Wrap beaker in insulating foam - reduce thermal energy transfer
- Connect joulemeter to immersion heater and power pack
- Leave for 30 min
- Read joulemeter
- Read final temp of liquid
Formula for SHC
c = change in energy
/
mass X temp change
Sources for inaccuracy for SHC + improvements
- Thermal Energy passing out of beaker == use insulator with low TC
- Not all thermal energy passing to liquid == ensure immersion heater is fully submerged
- Incorrect reading of thermometer == use electronic temp probe
- Thermal energy not spread in liquid == stir
Efficiency formula
Useful output/total input
3 fossil fuels
coal, oil, gas
Advantages of fossil fuels
- Reliable
- Release great deal of energy
- Abundant and cheap
- Versatile - use them for many things
Cons of fossil fuels
- Release co2 - global warming
- non renewable - not being replensished as we us them - one day run out
- Release other pollutants
What does burning diesel release
carbon particles and nitrogen oxides
What does burning coal release?
Sulfur dioxide = acid rain
What is a renewable energy source?
one that is being replenished as its used
Examples of renewable energy resources
- wind power
- solar power
- hydroelectric power
- tidal power
- biofuels
- geothermal
- wave power
Pros of all renewable energy resources
- never run out
- dont add co2 to atmosphere
cons of wind and solar power
- not reliable - days not windy/ cloudy
pros and cons of hydroelectric power
- reliable
- habitats are destroyed when dams are built and valleys are flooded
- only good is countries which have lots of rivers (not UK)
pros of tidal power
- reliable
cons of all renewable energy resources
- they only produce electricity
- energy mostly used in transport which runs on petrol/diesel which are fossil fuels
What is nuclear power
- Non renewable
- Run on urnamium and plutonium
PROS of nuclear power
- No co2 - doesnt contribute to climate change
- reliable - lots of electricity when we need it
cons of nuclear power
- highly dangerous radioactive materials- - if released into environment = disastrous
- decomissioning a power plant takes many yrs and expensive
- produces large amount of dangerous radioactive watse - needs to be stored for thousands of yrs before its safe
What does the UK have abundant reserves of?
coal
up until 1950s, all of electricity generated from coal
What happend when nuclear power came online in the 1950s
- by the 1980s, it produced around 20% of uks electricity
Benefits of burning gas over burning coal for electricity
- burning gas = less co2
- gas fired power stations are flexible - can be swiched on quickly during periods of high demand (short start up time), coal fired power stations have a long start up time
Econonmic factor to why politicians didnt see that fossil fuels were releasing co2
fossil fuels are cheap
switching away costs money and that could cost jobs
What is the Kyoto protocal
countries signed up to this and comitted themsleves to reduce green house gases emissions
Why is the UK in a good position to reduce greenhouse gas emissions
- wind-farms are built here because there is lots of space
future of uk energy
What is a baseload and which power is ideal for this?
- baseload = constant supply of electricity thats on all the time
- nuclear power - cant easily be turned on and off so tend to be on all the time, no co2 released
future of uk energy
What can we use for power in times of emergency in peak demand
- gas - fired power stations - switched on quickly
future of uk energy
What will renewables and other sources play a role in the future?
- Renewables = bulk of electricity
- nuclear = base load
- gas = peak demand
SHC method for a solid
- Measure mass of block
- Wrap into insulating layer to reduce energy transferred from block to surroundings
- Add few drops of water into thermometer hole otherwise there will be an air gap
- Insert thermometer and heater
- Measure initial temp of block
- Set pd of power supply to 10V and start stop watch
- Take readings of current and temp every minute for 10 minutes
- Turn off power supply and calc P = VI then E = Pt to find out energy
- Draw energy (x) and temp (y) graph
- calc gradient = 1 / (gradient X mass of block)
- repeat and compare with diff materials
RP 2:
Thermal insulators effectiveness of diff materials
- place small beaker in big beaker
- boil water and transfer 80 in small beaker
- cardboard for large beaker + hole for thermometer
- record starting temp and start stopwatch
- record temp every 3 min for 15 in (5 readings)
- repeat with same vol of water but add some insulating material to fill gap between 2 beakers
- test range of diff matierials with same mass (iv)
Why are gas-powered stations better than coal-powered stations?
- no acid rain
- less global warming
When the kettle, is on, why doesnt it quickly heat up the water?
heating element takes time to heat up
At the bottom of the slide, why is it that everyone has the same speed?
- decrease in potential energy = increase in kinetic
- masses cancel on both sides of equation
- speed only depends on vertical height
- variations will be due to friction
