PHYSICS TOPIC 1

?

energy stores and systems

energy is transfered between stores

THERMAL(INTERNAL ENERGY STORES),KINETIC,GRAVITAIONAL POTENTIAL,ELSTAIC POTENTIAL,CHEMICAL,MAGNETCI,ELECTROSTATIC,NUCLEAR

energy transfered mechanically-doing work- electrically or heating or radiation

energy transfered when system changes-single object

energy can be transfered away from system, between objects

closed syetms=matter and energy cant leave

net change always zero

1 of 30

energy transfers

HEATING

example-

kettle-water is SYSTEM, energy transfered to water -from kettle heating element - by heating into WATERS THERMAL ENERGY STORE

DOING WORK

when current flows or when moving an object

2 of 30

examples of energy transfers when doing work

THROWING A BALL

Force exerted by perosn throing ball DOES WORK

ENERGY TRANSFERS FROM CHEMICAL ENERGY STORES PEROSN ARM TO KINETIC EMNERGGY STORE OF BALL AND ARM

DROPPING A BALL

when dropped from height is accelertaed by gravity

gravitaional force does work

energy transfered from balls gravitational potential energy store to kinetic

CARS  BRAKES

friction between brakes and wheels does work

energy transfered from wheels kinetci energy store to to thermal energy in surroundings

3 of 30

examples of energy transfers when doing work

COLLISION BETWEEN CAR AND STATIONARY OBJECT

normal contact force between car and obkect does work

energy transfered from cars kinetic energgy store to other energy stores for exmaple elastic potential and thermal energy of object and car body

some energy transfered away by sound waves

4 of 30

kinetic and potential energy stores

anything moving has kinetic energy

energy transfered to this store when when obkect speeds up

energy transfered away when slowing down

kinectic energy store deends on objects mass and speed

gteater the mass and faster the more energy in kinetic energgy store

KINETIC ENERGY=1/2 X MASS X SPEED 2 -SQUARED-

5 of 30

gravitational potential energy

lifiting object in gravitaionla field requires work

this causes transfer of energy to gravitatinal potentail energy store of raisied object

higher the object more energy tranfered

amount depends on mass height and strength of gravitational field its in

GPE-J-=MASS-KG- X GFS-N/KG X H-M

WHEN SOMETHING FALLS ENERGY FROM GRAVITATINAL ENERGGY STORE TRANSFERED TO ITS KINETIC ENRGY STORE

ENERGY LOST FROM GPE STORE=ENERGGY GAINED IN KINETIC ENERGY STORE

AIR RESISTNACE ACTS AGAINST FALLING OBJECT

SOME ENERGY TRANSFERED TO OTHER ENERGGY STORES LIKE THERMAL TO SURROUNDING

6 of 30

specific heat capacity

how much energy needed to raise temperature

more energy neede to transfer to thermal energy stores than others to increase temperature

need gain alot of energy in thermal energy stores to heat up

CHANGE IN THERMAL ENERGY=MASS X SPECIFICHC X TEMP CHANGE

7 of 30

investigating specific heat capacity

use solid material -like copper- with two holes in it

1.meausre mass of block and then wrap in insulating layer to REDUCE ENERGY TRANSFERED FROM BLOCK TO SURROUNDINGS

2.INSERT THERMOMETER AND HEATER

3.measuer initial temp of block

set potentila difference of supply to 10v

turn on power supply and start stopwatch

4.when power turned on CURRENT IN CIRCUIT DOES WORK ON HEATER

ENERGY TRANSFERED ELECTRICALLY FROM POWEWR SUPPLY TO HEATERS THERMAL ENERGY STORE  BY HEATING CAUSING TEMP TO INCREASE

5.take reading of temp and current every min for 10 mins

6.turn off power supply calculate power supplied  by heater

8 of 30

investigating specific heat capacity

using this calculate power supplied by heater at each time of each temp reading

ENERGY=POWER X TIME

PLOT GRAPH

TEMP ON Y AND ENERGY TRANSFERED ON X

SPECIFIC HEAT CAAPCITY OF BLOCK

1 DIVIDED BY (GRADIENT X MASS OF THE BLOCK)

REPEAT WITH DIFFERNT MATERIALS

9 of 30

conservation of energy and power

CONSERVATION OF ENERGY PRINCIPLE-ENERGY CAN BE TRANSFERED USEFULLY, STORED OR DISSIPATED BUT CAN NEVER BE CREATED OR DETROYED

when energy transfered between stores NOT ALL transfered usefully, some dissipates-watsed energy-

for exmaple-

A MOBILE PHONE

energy usefly transfered from chemicla energy store in battery to but some dissipated to thermal energy stores of phone

CLOSED SYSTEM, COLD SPOON

when dropped into insultaed falsk, which then sealed. energy transfered from thermal energy store of soup to uselss thermal emergy of spoon-causing soup cool down slightly

10 of 30

power

power is the rate of doing work

measured in watts one watt=1 joule energy transfered per secons

power = enerrgy transfered divided by time

11 of 30

conduction and convection

CONDUCTION MAINLY OCCURS IN SOLIDS

IS THE PROCESS WHERE VIBRATING PARTCLES TRANSFER ENERGY TO NEIGHBORING OARTCLES

partcles being heated vibrate and collide with each other, these collisioms cause energy transfered between partcles kinetic energy stores

contines untill all energy transfered to other side of object

yhen transfered to surrounding thermal energy stores

THERMAL CONDUCTIVITY=HOW QUICKLY ENERGY IS TRANSFERED THROUGH A AMATERIAL

HIGH THERMAL CONDUCTIVITY MEANS ENERGY TRANSFERED BETWEEN PARTCLES QUICKER

12 of 30

conduction and convection

CONVETCION OCCURS MAINLY IN LIQUIDS AND GASES

WHERE ENERGETIC PARTCLES MOVE AWAY FROM HOTTER TO COOLER REGIONS

ENERGY TRANSFERED BY HEATING

energy shared across kinetic energy stores of gas or liquids particles

PARTCLES BALE TO MOVE and move fast so space between partcles incrrases causing density to decrease

warmer less dense regions will rise baove denser cooler regions

constnat heat sourec=convection current

13 of 30

energy transfoered from radiator to nearby partcles by conduction

air by radiator becomes warmer and less dense-particles moving quicky-

warm air rises and is replace sby cooler air

same time previously heated air transfers energy to surroundings it coos and become less dense and sinks

this is  CONVECTION CURRENT

14 of 30

reducing unwanted energy transfers

LUBRICATION

reduces frictional forces

when soemthing moves nomally frictional force acting against it

causing some energy to dissipate

when objects rubbed together LUBRICANTS CAN BE USED to reduce friction between objcets surfaces when they move

like liquids they can flow eaily between objects

15 of 30

reducing unwanted energy transfers

INSULATION

reduces rate of energy transfer bu heating

HAVE THICK WALLS MADE FROM MATERIAL WITH LOW THERMAL CONDUCTOR EMANING SLOWER RATE OF ENERGY TRANSFER WILL BE

EXAMPLES-

-some houses have cavity walls made up of inner and outer wall with air gap in middle

air gap REDUCES AMOUNT energy transfered by conduction though walls

cavity wall insultaion-air gap filled with foam reduces it too

-LOFT INSULATION redice convection surrents created in lofts

-DOUBLE GLAZED WINDOWS air gao between to prevent energy transfer by conduction

-DRAIGHT EXCLUDERS AROUND DOOR AND WINDOWS

16 of 30

investigating the effectiveness of materials as th

1.boil water in kettle pour some in SEALABLE CONATINER TO SAFE LEVEL

measuer masss in conatiner

2.use thermometer meausre initial temo

3.seal conatiner leave 5 mins measure using stop watch

4.remove lid and meausre final temp water

5.pur away water and allow water cool room temp

repeat but wrap conatiner different materials WHEN SEALED

COULD ALSO INVESTAIGET THICKNESS OF LAYER

SHOUDL FIND THICKER INSULATOR SMALL TEMP CHANGE OF WATER SO LESS ENERGY TRANSFERED

THICKER LAYERS=BETTER INSULATORS

17 of 30

efficiency

less enrgy wasted -usually as thermal- the more efficent it is

inprove efficiency=lubricating, indulating or making object more streamlined

EFFICIENCY=USEFUL OUTPUT ENERGY TRANSFER DIVIDED BY TOTAL INPUT ENERGY TRANSFER

EFFICIENCY=USEFUL POWER OUTPUT DIDVIDED BY TOTAL POWER INPUT

USEFUL ENERGY INPUT NOT EQUAL TO TOTAL ENERGY OUTPUT

why-some wasted thermal energy stores

APART FROM ELECTRIC HEATERSALL ENERGY IN ECETROSTAIC ENERGY STORE TRANSFERED TO USEFUL THERMAL ENERGY STORES

18 of 30

energy sources and their uses

NON-RENEWABLE ENERGY SOURCES-will run out one day

fossil fuels and nuclear fuel-urnaium and plutonium-

coal,oil, and -natural-gas

all damage environemnt

RENEWABLE RESOURCES WILL NEVER RUN OUT

sun, wind,water waves,hydro-electricity,bio-fiel,tides,geothermal

most do damage environement but less so

dont provide as much energy and some un-reliable as they depend on the weather

19 of 30

energy sources and their uses

NON RENEWABLE-

PETROL AND DIESEL USE FUEL CREATED FROM OIL

COAL

RENEWABLE-

VEHICLES THAT RUN ON BIO-FUELS

WHEN HEATING-

NON RENEWABLE-natural gas, used to heat water which is pumped through radiators,coal,electric heaters

RENEWABLE-geothermalheat pump uses geothermal energy resources,solar water heatersuse sun to heat water,burning bio fuel

20 of 30

wind solar and geothermal

WIND POWER

each turbine has generator inside produce electricicty

no pollution

SPOIL VIEWS NEED 1500 TO REPLACE ONE COALR-FIRES POWER STATION

very noisy

stop when wind stopsor too strong

impossible to increase supply when high demand

initail costs high but no fuel costs and minimla running costs

no permamnet damage to landscape

21 of 30

wind solar and geothermal

SOLAR CELLS

expensive but no environemental damage

no pollution

very reliable when sunny

cant increase power oitput when extra demand

initail cost high but runnong cost free

generate on small scale

22 of 30

wind solar and geothermal

GEOTHERMAL POWER

volcanic areas

enery is the slow decay of radioactive elements including urnaium deep inside earth

reliable little damage

generate electricity or heat buildings

not very suitable locations for power plants and cost building them high comapred to amaount energy produces

23 of 30

hydroelectricity, waves and tides

HYDRO-ELECTRIC POWER to generate electrcicity

requires flooding of a valley by building a dam, water allowed trhough turbines

no pollution

big impact on environment due to flooding

rotting vevegtation reelases methane

resevoirs can look unsightly when dried up

can create immediate response to increase in demand

initial costs high but no fuel cost and minimla running cocts

24 of 30

hydroelectricity, waves and tidesr

WAVE POWER-

need many small wave powered turbines ocated around coast

no pollution

disturbs seabed and habitats of marine animals  spoling views

failry unreliable

initial costs high

no fuel costs

wave power no energy on karge scale

25 of 30

hydroelectricity, waves and tidesr

TIDAL BARRAGES

big dams with turbines in them built across river esturaies

as tide comes in fills up esturary

water aloowed through turbines at controlled speed

tides produced by graviationla pull of sun and moon

no pollution

aleters habitas and spoils views

relaible

height of tide varaibale so lower tides will provide less energy

initial costs high but no fuel cost

26 of 30

bio fuels and non renewables

bio duels are renewable energy sources made from plant produce or animla dung

failry reiable-crops grown all year round and take long time to gro

cannot respond to immediate demands

to coabte they are stored and continously grown

cost to refine them is big and some worry not enough to meet demands of crops for food

some areas large amounts forest cleared to grow biofuels menaing loss habitat

when burning imcreases co2 and methane emissions

27 of 30

bio fuels and non renewables

non-renewable are reliable

eneough fossil and nuclear fuels to meet demand

however slowly running out

running cots not expensive low fuel extraction prices

cost efficent

BUT CREAT ENVIRONEMNTAL PROBLEMS

coal il and gas release co2 into atmopohere adding to GREENHOUSE EFFECT

relases sulfur dioxide causing ACID RAIN HARMFUL TO TREES AND SOIL

acid rain can be reduced by taking sulfur out before fuel burnt

coal mining makes mess of landscape

oil spillages harms animals and sea creatures

28 of 30

bio fuels and non renewables

nuclear power clean but nuclear waste dangerous and hard to dispose

nuclear fuel-urnaium-cheap but overall cost of nuclear power high

29 of 30

trends in energy resource use

introducing more renewable energy resources

pressure from other countries and public

puts pressure buisnesses create new power plamnst so dont go out of buisness

cra companies and hybrids and ekectric cars

RENEWABLE ENERGY LIMITED BY RELIABILITY MONEY AND POLITICS

building new power planst costs money so energy providers reluctant espeically as fossil fuels cost effective

bills taxes etc

where to put new ones

some not as reliableor cant increase power output on demand

expenive hybrid cars

30 of 30