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year 10 physics > energy > Flashcards

energy Flashcards

(70 cards)

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1
Q

what are the golden rules for energy?

A

Energy cannot be created or destroyed
it can only be transferred from one store
to another store.

ENERGY IS MEASURED IN JOULES (J)

ENERGY IS MOVED FROM ONE ENERGY
STORE TO ANOTHER (‘TRANSFER’) by
MECHANICAL WORK, ELECTRICAL WORK,
HEATING, OR RADIATION

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2
Q

what does energy allow?

A

ENERGY ALLOWS WORK, RADIATION AND HEATING TO BE DONE.

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3
Q

how is energy transferred mechanically?

A

when a force moves something through a distance.

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4
Q

how is energy transferred by heating? (H)

A

when a temperature difference causes a transfer of energy from one place to another by conduction or convection.

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5
Q

how is energy transferred electrically?

A

when an electric charge moves through a potential difference; this is the main method of energy transfer in electric circuits.

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6
Q

how is energy transferred by radiation? (R)

A

carried by waves in the electromagnetic spectrum (this includes Radio, microwaves, infra-red, visible light, ultra-violet, x-rays and gamma), or by mechanical waves such as sound.

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7
Q

what is conduction?

A

how thermal energy flows through a substance without moving.

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8
Q

what is convection?

A

transfer of heat through fluids by the upwards movement of warmer, less dense regions of fluids.

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9
Q

how does heat move?

A

heat moves from somewhere hot to somewhere cold.

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10
Q

what are the best conductors of heat?

A

solids and metals

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11
Q

what are the worst conductors of heat?

A

gasses

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12
Q

what is a poor conductor called?

A

an insulator

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13
Q

does a vacuum allow conduction or convection?

A

no

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14
Q

how does thermal conduction occur by molecules?

A

the molecules vibrate when heated, intermolecular forces allow the molecules to pass their vibrations from one to another. the stronger the forces the faster vibrations are passed.

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15
Q

how does conduction occur through metal?

A

they have electrons that can move from one atom to another. these electrons can pass energy through the metal very quickly.

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16
Q

why is diamond a good conductor?

A

because it has strong intermolecular bonds

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17
Q

how do you speed up the rate of thermal transfer?

A

by using a better conductor
by decreasing the thickness of the substance
by increasing the are of the substance
by increasing the temp difference across the substance

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18
Q

what is thermal radiation?

A

the transfer of energy by infrared waves

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19
Q

which surfaces emit radiation the best

A

dark, rough surfaces.

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20
Q

which surfaces absorb radiation the best

A

dark, rough surfaces

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21
Q

which surfaces reflect radiation the best

A

bright, polished surfaces

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22
Q

name a method of heat transfer in solids. Describe, in terms of particles, how energy is transferred through the solid block by this method.

A

conduction because the molecules vibrate when heated, intermolecular forces allow the molecules to pass their vibrations from one to another.

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23
Q

where can convection not take place and why?

A

in solids because convection travels fluids not solids as the particles in a solid are tightly bonded and you need them to flow for convection.

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24
Q

when humans are cold the hairs on their bodies stand on end. explain how this reduces heat loss in the body.

A

when the hairs stand up they trap a layer of air and air is a good insulator.

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25
suggest one way in which heat loss can be reduced from the human body.
wearing clothes because when you wear clothes they trap a layer of air is a good insulator.
26
A homeowner is considering having a cavity wall insulator installed. state one transfer this will help reduce.
conduction because cavity insulated walls stop the hot air from rising.
27
how is heat loss reduced in doors, windows, roofs, floors and walls?
``` doors - draught excluders windows - double glazing/curtains roof - lost insulation floors - carpets walls - cavity wall insulators ```
28
how can you reduce heat loss in a flask?
conduction - reduced by the vacuum, stopper, glass, cork and air spaces convection - reduced by the vacuum, stopper and the trapped air spaces radiation - reduced by the silvered walls.
29
what is energy needed for?
energy is needed to: - heat up objects - make objects move - keep your body alive
30
where is energy stored?
energy is stored in everything, anything that happens anywhere involves energy.
31
name the types of energy stores
``` chemical energy store heat energy store kinetic energy store (KE) nuclear energy store elastic potential energy store gravitational potential energy store (GPE) ```
32
where is chemical energy stored?
inside chemicals. eg. batteries, food, fuel...
33
where is heat energy stored?
in high temp objects
34
where is kinetic energy stored?
stored in anything that's moving
35
where is nuclear energy stored?
the nuclei in the atoms of all materials
36
where is elastic potential energy stored?
something 'elastic'
37
where is gravitational potential energy stored?
in objects above the ground
38
what is the law of conservation energy?
you cannot create or destroy energy. it can only be transferred from one store to another.
39
how do you find the efficiency of something?
useful energy output / total energy input x 100
40
how is energy measured
in joules (J)
41
what is useful energy and wasted energy?
useful energy is energy transferred to where it's required in the form that it's wanted. other forms of energy are referred to as wasted. wasted energy spreads out into the surroundings.
42
how do you improve efficiency?
- reducing friction by using lubricant (eg. oil) - reducing electrical resistance by using streamline shapes. - reduce loss to sound by tightening the loose parts of machinery.
43
how is work done?
when a force caused a body to move through a distance, energy is transferred and work is done.
44
how are work and energy measured?
in joules (J)
45
how do you work out the work done?
= force applied x distance (moves in direction of force) | w = f x d (W = joules, F = newtons, D = meters)
46
what is GPE
Gravitational potential energy is the energy stored in an object as the result of its vertical position or height.
47
how do you work out the gpe
= mass x gravitational field strength x height (mge)(gpe = joults, mass = kg, g = newtons per kilograms [N/kg] - always 10)
48
what is kinetic energy
the kinetic energy of an object is the energy that it possesses due to its motion.
49
how do you work out kinetic energy?
KE = 1/2 x m x v^2 (m = mass - kg, ke = kinetic energy - joults, v = speed - seconds)
50
what is power?
power is a measurement of how quickly work is done.
51
how do you work out power?
P = work done / time taken (power - P = watts [W], work done - W = joules [J], time - T = seconds [S])
52
what is a renewable energy source?
a renewable energy resource is one that will not run out. renewable energy sources do not produce radioactive waste, greenhouse gas or acid ain.
53
what are examples of renewable energy?
wind, hydroelectric, wave, tidal, solar, geothermal
54
fill in the gaps: convection is a method of heat transfer the only occurs in ...... . When part of a fluid is heated the .... in that region move ...... and take up more space. The heated fluid expands and becomes ..... than the surrounding cooler fluid. the heated fluid .... on top of the cooler fluid. the upwards path of the heated fluid is called ..... current.
- fluids - molecules - faster - denser - rises - convection
55
what is an example of a non - renewable energy source?
coal, gas, oil or uranium
56
what is a generator?
a generator is something that if it is turned, will produce energy.
57
explain wind power and state the energy changes.
a wind turbine - the wind is used to rotate a turbine which turns an electrical generator. ec - kinetic to electrical
58
explain hydroelectric power and state the energy changes.
hydroelectric power station - falling water is used to drive a turbine which rotates an electrical generator. ec - GPE to KE to electrical
59
explain wave power and state the energy changes.
wave power generator - waves can be used to drive an electrical generator. ec - KE to electrical
60
give an example of tidal power, explain it and state the energy changes.
tidal power generator - moving water caused by tides rotates a generator. ec - GPE to KE to electrical
61
explain geothermal power and state the energy changes.
geothermal power station - in some volcanic areas hot water and steam rise to the surface. the steam is trapped and used to drive turbines which turn electrical generators. ec - thermal to KE to electrical
62
explain solar heating and state the energy changes.
solar heating generators - heat energy from the sun is focused onto pipes containing water. the water boiled producing steam. the steam is then used to drive turbines which turn electrical generators. ec - thermal to KE to electrical
63
explain solar cells and state the energy changes.
solar panels - electricity produces directly from the sun's radiation. ec - light to electrical
64
explain the advantages and disadvantages of wind power
advantages - renewable - doesn't produce any greenhouse gasses - doesn't produce acid rain - doesn't produce radioactive waste - short start uptime - inexpensive disadvantages - unreliable - need wind - considered unsightly - many turbines are needed to produce energy - noise - danger to wildlife
65
explain the advantages and disadvantages of hydroelectric power
advantages - renewable - doesn't produce any greenhouse gasses - doesn't produce acid rain - doesn't produce radioactive waste - short start uptime disadvantages - limited locations - wildlife affected - expensive
66
explain the advantages and disadvantages of wave power
advantages - renewable - doesn't produce any greenhouse gasses - doesn't produce acid rain - doesn't produce radioactive waste - short start uptime - no land is needed - inexpensive disadvantages - unreliable - limited areas with suitable waves - prone to storm damage - need lots - gets in the way of ships
67
explain the advantages and disadvantages of tidal power
advantages - renewable - doesn't produce any greenhouse gasses - doesn't produce acid rain - doesn't produce radioactive waste - short start uptime - no land is needed disadvantages - limited locations - wildlife affected - expensive
68
explain the advantages and disadvantages of geothermal energy
advantages - renewable - doesn't produce any greenhouse gasses - doesn't produce acid rain - doesn't produce radioactive waste - short start uptime disadvantages - VERY limited locations - expensive to build
69
explain the advantages and disadvantages of solar heating
advantages - renewable - doesn't produce any greenhouse gasses - doesn't produce acid rain - doesn't produce radioactive waste disadvantages - sunshine is needed so only best in desert regions - can only be used during the day - large amounts of land are needed to produce significant amounts of energy
70
explain the advantages and disadvantages of solar cells
advantages - renewable - doesn't produce any greenhouse gasses - doesn't produce acid rain - doesn't produce radioactive waste - instant start uptime disadvantages - sunshine is needed so could be unreliable - can only be used during the day - only 10% of solar energy is converted into electricity - lots of cells are needed to produce significant amounts of energy

year 10 physics (1 decks)

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