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physics > energy > Flashcards

energy Flashcards

1
Q

what is the rule for energy

A

it is never created or destroyed but only transferred between different objects and forms

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2
Q

list some energy stores

A

thermal -heat
kinetic-movement
gravitational potential-position in gravitational field
elastic potential- held in already stretched spring
chemical-held by chemical bonds
magnetic
electrostatic
nuclear-breaking atoms apart

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3
Q

what are the 4 ways we can transfer energy

A

mechanically-physically stretching an elastic band
heating-
through radiation -like light or sound waves
electrically-plugging item into socket

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4
Q

what happens when a system changes and how does it happen

A

energy is transferred between different objects or different forms

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5
Q

what is a system

A

collection of matter

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6
Q

what can happen in an open system that cant in a closed-give an example

A

no matter or energy can leave so overall change is 0

kettle is connected into plug socket
electrical energy flows to heating element(Transferred electrically) of store warming metal heating element transferring it to the waters thermal energy store

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7
Q

what is work done = to and what are the 2 types

A

it equals energy transferred

mechanical(using force to move object)-chemical energy from your leg when kicking a ball transferred to kinetic energy store of ball
and electrical(when current flows) energy required to overcome resistance in the wires of a circuit

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8
Q

what is the equation for kinetic energy

A

e =1/2 mv2

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9
Q

what is the equation for gravitaional potential energy

A

e=mgh

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10
Q

what is the equation for elastic potential energy

A

e=1/2ke2(extension-m)
(spring constant-N/m)

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11
Q

what is the equation for thermal energy

A

E=mc x change in temp

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12
Q

efficiency equation

A

useful nrg out/total nrg in x100
or power

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13
Q

what are some finite energy sources

A

coal oil/natural gas

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14
Q

what are renewable

A

wind/hydoelectric/solar/geothermal/biofuel

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15
Q

what is internal enrgy

A

sum of potential/kinetic energy

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16
Q

what is specific latent heat

A

energy required to change state of substance

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17
Q

what is the relation of mass and speed and kinetic energy

A

the faster an object moves the more kinetic energy it has
the more mass an object has the more kinetic energy it has if everything else is constant

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18
Q

how many kilos in a tonne

A

1000

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19
Q

what is gravity

A

the force of attraction between 2 objects which is dependent on mass and the distance between the objects

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20
Q

what is the gravitational field strength on the earth and mars

A

9.8N/kg and 1.6N/kg

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21
Q

what is weight

A

the force of attraction an object experiences when entering a gravitational field

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22
Q

weight/ mass and gravitational field strength

A

w=m(kg)g(9.8)

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23
Q

what is the formula for gravitational potential energy

A

ep=mgh
kg/n/kg/m

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24
Q

what is gpe

A

the energy transferred to the objects potential energy store to lift up an object

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25
Q

as an object rises what happens

A

ke is converted to gpe

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26
Q
A
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27
Q

gpe or ke lost=

A

ke gained or gpe gained

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28
Q
A
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29
Q

what is internal energy

A

potential energy stores and kinetic energy stores
-total energy stored by particles of a substance

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30
Q

what is the equation for specific heat capacity

A

change in internal energy=mass x spec heat capacity x change in temp

30
Q

what is the specific heat capacity

A

amount of energy needed to raise the temp of 1 kg of a substance by 1 degrees

30
Q

what is temperature

A

average internal energy of a substance

30
Q

v

A
30
Q

what is conservation of energy

A

energy can be transferred stored or disspated but cant be created or destroyed

30
Q
A
31
Q

what forms can wasted energy come as

A

heat mainly

31
Q

what are the 3 ways heat is transferred

A

conduction in solids
convection in liquids
radiation through empty space

32
Q

why does conduction mainly happen in solids

A

as they collide a lot unlike in liquids or gases where they are spread out

33
Q

what do you use to measure how well objects transfer energy by conduction

A

thermal conductivity

34
Q

what is convection current

A

hotter particles spread out and are replaced by colder particles which go near heat source and then these cool down and repeat

35
Q

what are some example of convection current

A

radiation and oceans

36
Q

what does a fluid refer to

A

a substance that has particles that are free to move like liquids or gases

37
Q

how do we reduce thermal energy that escapes our house

A

ensure door is sealed closed(convection so air cant escape)

thick cavity walls(with low thermal conductivity)

38
Q

conduction vs insulation

A

conduction is how heat moves through a material

insulation is keeping heat and not allowing it to flow

double glazed windows

39
Q

how do we reduce friction

A

using lubricants
making cars and planes streamlined

40
Q

what is the 1st equation for power

A

power is the rate at which energy transferred
p=e/t

41
Q

2nd equation for power

A

p(watts)=w(joules)/t(s)
power is the rate that work is done

42
Q

why is no device 100% apart from some

A

they all produce some form of waste mainly thermal energy

apart from heaters which all energy would go into heat

43
Q

what are some non renewable energy sources

A

coal
oil
natural gas
nuclear energy

44
Q

what are some renewable resources

A

solar
wind
hydroelectric
geothermal
tidal
biofuels

45
Q

what non renewable energy mainly used for

A

natural gas for cooking
coal for fireplaces
crude oil for petrol and diesel(transport)

46
Q

what is a renewable form of heating

A

biofuels can be burned for heat just like coal

solar water heaters use suns energy to heat water and pump through our heaters

47
Q

Explain the difference between renewable and non-renewable energy resources. Use an example for each.

A

A renewable energy resource is one that is being replenished as quickly as it is used. For example solar energy is renewable because new sunlight is always being generated by the sun - we don’t use it up.

A non-renewable energy resource on the other hand is one that isn’t being replenished and so has a limited supply. For example fossil fuels like coal are non-renewable because they’re not being replenished and at some point coal could run out.

48
Q

what are some ways fossil fuels can be used

A

to generate electricity
burned to provide heat
to generate electricity

49
Q

what are the pros and cons of fossil fuels

A

pros

-relatively cheap
-can be used in any condition(dont require certain like sunlight)
-many of our modern infrastructure are designed to run on it

cons
-limited
-produce co2 when burned so contribute to global warming
-produce toxic gases when burned

50
Q

pros and cons of nuclear energy

A

Pros
-dont produce any pollutants
-used in any conditions
-unlikely to run out in a long time

Cons
-finite
-produce years of radioactive waste which remain harmful for 1000s of years
-expensive
-small chance of nuclear meltdown/accident

51
Q

what is wind power/how is it generated and used

A

caused by wind turbines with a generator turns generator when wind flows which converts kinetic energy from movement electrical energy which is sent to national grid

52
Q

what is solar power

A

solar cells generate electric current from sunlight
-in watches or calculators
can be used to generate eletricity for towns

53
Q

what are pros for solar and wind energy

A

pros-

-low running costs
-no pollutants produced
-dont damage environment
-get cheaper every year

cons-
-weather dependent
-no way to increase supply in peak demand
-take up lots of space
-high up front costs
-production produces pollutants

54
Q

what is geothermal energy/uses

A

thermal energy generated and stored in earths crust

used for heat and electricity

55
Q

what are cons/pros of geothermal energy

A

cons
-can only be used in certain areas
-power plants can be expensive to build

pros
-only damages environment slightly
-doesnt produce any pollutants while running
-reliable over long periods

56
Q

what are biofuels

A

fuels made from recently living organisms(plants or algae) as they photosynthesis and lock up suns energy which we release later when we burn for fuel

57
Q

why are biofuels carbon neutral

A

they took up co2 when they were growing and when they are burnt they release it so there is no overall release of co2

58
Q

what are pros and cons of biofuels

A

pros
-cheap to make
-easy to transport
-can be mixed with fossil fuels and used in vehicles we already have
-good substitute for fossil fuels

cons-
-processes release co2 and require lots of energy
-damage environments as we need large space to grow

59
Q

In theory biofuels should be carbon neutral, but in reality they are not.

A

Trees may be cut down, so no longer absorb CO2

Trees may be cut down, and will release CO2 if burned

Energy will be required to harvest, process and transport the biofuels…

… which will release more CO2

59
Q

what are the pros and cons of tidal and hydroelectricity

A

pros
-reliable
-low running costs
-large amounts of energy with 0 pollution

cons-
-often flood huge areas
-initial set up is expensive
-sometimes stop boat and fish travelling

60
Q

what are the variables for the spec heat capacity practical

A

independent-material type
dependent-temp rise
control-mass of material/surface of material

61
Q

list the spec heat practical equipment

A

heater
block of material
power supply/pack (10v)
Ammeter
wires
leads
thermometer
insulating material
stopwatch

62
Q

what are the steps for the practical of shc 8 steps

A

1)get block of material with a hole for the heater and the thermometer

2)Measure mass of block and wrap in insulating material(like foam or thick newspaper)
add heater and thermometer
3)measure the starting temp of the block and set the pd of the power supply as 10v
4)Turn the power supply on and start a stopwatch
5)Measure the temperature at eye level every minute for 10 mins
6)look at the ammeter to check if the current changes as it should stay constant
7)when all readings are collected turn off power supply
8)with data find materials spec heat capacity and repeat with differet materials

63
Q

how do you calculate spec heat capacity from your data

A

use p=vi to find out how much power has been supplied to the heater

then use e=pt to find energy transferred to the heater

plot graph of energy transferred(x axis) against temperature(y axis)

find gradient of straight part of the graph

spec heat capacity= 1/ (change in gradient x mass of the block)

64
Q

what is the equipment in the insulation practical (6 steps)

A

boil water in a kettle and pour into a beaker (sealable container) to a safe level

use thermometer to get starting temp of water

seal beaker and leave it for 5 mins measuring using stopwatch

remove lid and measure the final temp of the water

pour water away and let container cool at room temp

repeat experiment but wrap container in different material using same mass of water and reboiling water

65
Q

Why is it important to repeat the experiment?

A

To ensure accuracy and consistency of results

66
Q
A

physics (9 decks)

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