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Flashcards in TOPIC 3 Deck (21)
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1

3.4 what is conservation of energy

energy can't be created or destroyed, it can only be transferred from one store to another. this means the total energy transferred by a system is the same as the energy put into the system

2

3.5energy transfers- object projected upwards or up a slope

object does work against gravitational force so energy is transferred mechanically from kinetic energy store of the object to its GPE store

3

3.5energy transfers-- moving object hitting an obstacle

the moving object has kinetic energy so some is transferred mechanically to the obstacles kinetic energy store. some is transferred to the TE stores and surroundings by heating.

4

3.5energy transfers-- object being accelerated by a constant force

energy transferred from chemical energy mechanically to the kinetic stores

5

3.5energy transfers- vehicle slowing down

KE transferred mechanically, due to friction and then heating to TE stores of car and road

6

3.5energy transfers- boiling water

energy is transferred by electricity to TE store of water. some is lost as sound

7

3.6energy transfers in a closed system

where there are energy transfers in a closed system there is no net change to the total energy in that system

8

3.8energy transferred in not closed system

in all system changes, energy is dissipated and stored in less useful ways

9

3.7 when do mechanical processes become wasteful

mechanical processes become wasteful when they cause a rise in temperature so dissipating energy in heating the surroundings

10

3.9 how to reduce unwanted energy transfers- lubication

when there is friction energy transferred mechanically to TE of objects which is then dissipated by heating to surroundings
lubricants reduce friction

11

3.12how can efficiency be increased

reducing the amount of wasted energy. for mechanical processes this can mean reducing friction or finding ways to make sure all fuel going into an engine is burned or finding a way to use the energy transferred by heating

12

3.9- how to reduce unwanted energy transfers- insulation

slows down the rate at which energy is transferred out of a house by heating
s

13

3.10- effects of thickness and thermal conductivity on the rate of cooling

by increasing thickness of the wall, the slower the energy transfer
thermal conductivity - how well a material transfers energy by conduction, air had a low TC. the lower the thermal conductivity of walls, the slower the rate of cooling
ome houses have cavity with air gaps inside, the air reduces the amount of energy transferred by conduction as air has a low thermal conductivity, this helps to reduce energy transfers out of the house, keeping it warm

14

trends in uses of energy resources

20th century- use of electricity increased as the population got bigger and we used electricity for more things
21- use of electricity has decreased because people are trying to make appliances more efficient and we are being careful with the energy use in our homes. we are trying to increase the use of renewable resources to reduce pollution and made supplies of the fuels last longer

15

fossil fuels

non renewable
coal, oil, natural gas
we use oil to make petrol and diesel
natural gas is used to heat homes or for cooking
release carbon dioxide and contribute to climate change

16

nuclear fuel

don't emit carbon dioxide
but waste is radioactive and is expensive to dispose of safely and decommission nuclear power stations

17

biofuel

used in same ways as fossil fuels
made from animals waste and plants
carbon neutral- release same amount of co2 when they burn as they took from the environment when they grew

18

wind power

wind turbines are turned by the wind which turn generators and produce electricity
lots needed to produce the same amount of energy as fossil fuel stations

19

hydroelectricity

involves flooding a valley by building a dam. water it then let out through turbines to produce electricity
available at anytime and can be started and stopped very quickly unlike fossil fuels

20

tidal power

dams are built across estuaries with turbines in them. when the tide comes in it falls up the estuary, the water is then let out to generate electricity

21

solar power

use energy transferred by light to create an electrical current.
used on a small scale