P1 topic 5&6 Flashcards
1
Q
how is an ammeter connected in a circuit?
A
in series
2
Q
which way does conventional current flow?
A
from positive to negative
3
Q
how is an voltmeter connected in a circuit?
A
it’s connected in parallel across the component
4
Q
potential difference/voltage
A
the amount of energy transferred per unit charge
5
Q
electrical power
A
the rate of energy transfer or the rate of work done
6
Q
fuse
A
a very thin piece of wire that acts as a safety device in a mains plug- if a fault occurs and the current becomes too high, the fuse will melt and break the circuit, preventing further damage or a fire
7
Q
current
A
the rate of flow of charge
8
Q
what are dull black surfaces?
A
good radiators and absorbers of heat radiation
9
Q
what is a bright shiny surface?
A
a poor absorber and radiator of heat- it reflects the heat radiation away
10
Q
what will happen to objects that are warmer than their surroundings?
A
they will emit more energy per unit time than they absorb
11
Q
what is the link between all objects and infrared radiation?
A
all objects emit, absorb and reflect infrared radiation
12
Q
what does the amount of infrared radiation an object emits depend on?
A
its temperature and its surface
13
Q
what do all objects greater than absolute zero do?
A
they emit infrared radiation- the hotter an object, the more power it radiates
14
Q
thermal equilibrium
A
when the rate of heat absorption equals the rate of heat radiation and the temperature of an object remains steady
15
Q
when will temperature rise?
A
when the rate of absorption is greater than the rate of radiation
16
Q
what do all atoms have?
A
kinetic energy (due to their vibrations) and potential energy (due to their position)
17
Q
heat energy of a substance
A
total kinetic energy and potential energy of all the atoms in a substance
18
Q
how can you investigate the different rates of heat radiation of different surfaces?
A
you can compare the temperature over time of a silvered beaker and a blackened one
19
Q
how can you investigate the different rates of heat absorption?
A
you can use a radiant heater between two copper plates- one silvered and one blackened- time how long it takes for each plate to get hot enough to melt some wax
20
Q
thermal energy
A
an object at a higher temperature has greater thermal energy
21
Q
light energy
A
light is a wave that is emitted from anything at a very high temperature
22
Q
electrical energy
A
this is usually associated with electric current
23
Q
sound energy
A
an object vibrating will emit sound
24
Q
kinetic energy
A
this is energy due to movement
25
chemical energy
this is energy stored by atoms
26
nuclear energy
this is energy stored by the nuclei of atoms
27
elastic potential energy
an object that is pulled or squashed has this type of energy
28
gravitational potential energy
this is energy due to an object's position in the Earth's gravitational field- an object lifted higher will have greater gravitational potential energy
29
examples of thermal energy
heater, the Sun, hot water
30
example of light energy
lamp, stars, fire
31
examines of electrical energy
mains supply, overhead cables, output from a transformer
32
examples of sound energy
buzzer, bell, siren, person talking
33
examples of kinetic energy
person running, high-speed train, planet orbiting the sun
34
examples of chemical energy
food, chemical cell, coal
35
examples of nuclear energy
nuclear power station, radioactivity, nuclear bombs
36
examples of elastic potential energy
a stretched rubber band, cables supporting a bridge
37
examples of gravitational potential energy
aeroplane in the sky, person up a ladder
38
what must happen when anything moves or changes?
an energy transfer must happen
39
principle of conservation of energy
energy cannot be created or destroyed; it can simply be transferred from one form to another- total energy input must be equal to risk beefy output
40
what is the useful energy transferred in a lightbulb?
light
41
what is the water energy transferred in a lightbulb?
heat
42
what is the most common form of wasted energy?
heat- the heat energy produced may be due to electric currents flowing in wires or due to friction between moving surfaces
43
efficiency
a measure of how well a device transfers energy in the form we want- the proportion of input energy that is transferred to useful form
44
sankey diagrams
energy-transfer diagrams that die the different forms energy takes during a transfer-thickness of arrow is drawn to scale to show the amount if energy transferred
45
when is a voltage induced? what is electromagnetic induction?
when a wire is moved in a magnetic field- if the piece of wire is part of a circuit, a current will flow
46
how is the direction of current reversed?
when the motion of wire is reversed or when the magnet is turned around
47
when is a voltage anyways induced?
when there is relative movement between a magnet and a coil of wire- the induced voltage is larger when the magnet is moved more quickly
48
what do you need in order to generate electricity?
a magnet, a coil of wire and movement
49
how do you create a continuous induced current?
you must keep the magnet moving relative to the coil of wire- it doesn't matter whether the coil or the magnet moves
50
how can the size of an induced current be increased?
putting more turns in the coil, using an iron core inside the coil of wire, stronger magnets, faster movement
51
how do bicycles produce energy for their lights?
using dynamos- wind up radios and torches also use them
52
generator
electricity induced in the coil of the generator is transferred to a circuit through the slip rings, which touch carbon brushed attached to the circuit- sling rings and bridges allow electricity to flow between the moving coil and stationary circuit without wires getting twisted
53
electrical generator
a coil is rotated in a magnetic field- as the coil rotates, it cuts the magnetic field lines to induce a voltage across the coil- the coil has slip rings, which are connected to a circuit via brushes- this causes an alternating current to flow in the circuit
54
direct current
always flows in the same direction- cell provides direct current
55
alternating current
changed direction at a frequency determined by a rotating coil
56
what frequency is mains electricity generated at?
50 Hz
57
what does the variation with time follow?
a sinusoidal curve
58
transformer
a device that converts the voltage of an alternating current supply to another voltage
59
what is a transformer made up of?
two coils of wire are wrapped around a soft iron core- the ac voltage supply is connected to the primary coil and the output ac voltage is induced across the secondary coil
60
step up transformer
conveys a low voltage input to a higher voltage output- the primary coil will have fewer turns than the secondary coil
61
step down transformer
confess a fight voltage input to a Lowe voltage output- the primary coil will have more turns than the secondary coil
62
national grid
network of pylons, high voltage cables and transformers that carries electricity from power stations across the country
63
how are step up transformers used in the national grid?
they increase the 23kV power station output to higher voltages (275kV or 400kV) reducing heat loss in the cables and improving efficiency of transmission
64
how are step down transformers used in the national grid?
they lower the voltage to 230V, which is safer for homes
65
why can overhead cables cause serious harm?
electricity transmission is hazardous- the cables are not insulated, so they can cause serious harm or even death if they are touched
66
how can risks of electricity cables be reduced?
risks can be minimised by burning cables underground, but this makes it expensive and difficult to maintain cables- suspending them fro. pylons is a cheaper option
67
how is an ac voltage induced in a transformer?
the ac voltage in the primary coil of a transformer creates and ever-changing magnetic field around it- the magnetic soft iron core channels the magnetic field through the secondary coil- the alternating magnetic field will continuously cut through the wires in the secondary coil and the ac voltage will be induced
68
what sort of current do transformers only work with?
alternating current
69
why are coal, oil and natural had called fossil fuels?
they are formed from the remains of prehistoric plants and animals
70
why are fossil fuels and nuclear firms non renewable resources?
they cannot be replaced and will eventually run out
71
advantages of coal
fuel is cheap, coal-burning power stations have a quick start-up time, coal will last at least 200 years
72
advantages of natural gas
gas-fired power stations are efficient and have the quickest start-up time so they are flexible at meeting demand for power, gas will last another 50 years, gas doesn't produce sulfur dioxide
73
advantages of oil
oil burning power statins have a quick start-up time, there is enough oil left to last 50 years
74
advantages of nuclear fuel
nuclear power statins are located far away from population centres, it died t product carbon dioxide or sulfur dioxide
75
disadvantages of coal
burning it produces carbon dioxide and sulfur dioxide, sulfur dioxide produces acid rain, mining can be dangerous, stockpiles are needed to meet demand
76
disadvantages of natural gas
burning gas produces carbon dioxide (although less than coal and oil), pipelines necessary for transporting gas are expensive
77
disadvantages of oil
burning oil release carbon dioxide and sulfur dioxide, oil prices are extremely variable, there is danger of spillage and pollution during transport of oil by road rail or sea
78
disadvantages of nuclear fuel
building and decommissioning a power station is expensive, start-up time is the longest; radioactive waste remains dangerous for thousands of years
79
solar power
turns light energy from the Sun into electrical energy, using solar cells
80
wind power
is used to rotate huge propeller blades on a turbine to generate electricity
81
wave power
generated when large floats containing coils and magnets move up and down with ocean waves
82
hydroelectric power
when fast-flowing water, stored in a reservoir above a power station is used to generate electricity
83
tidal power
used seawater from incoming and outgoing tides to create electricity
84
biomass
organic material from decaying plant or animal waste is used as fuel in power staton, in the sane way fossil fuels are-wood can be used in a power staton in a similar way
85
why don't we always use renewable resources?
although they cost nothing to use and produce no greenhouse gases, the cost of building renewable power stations is substantial
86
advantages of solar power
useful in remote areas, single homes can have their own electricity supply
87
advantages of wind power
can be built offshore
88
advantages of wave and tidal power
ideal for island countries
89
advantages of hydroelectric power
creates water reserved as well as electricity supplies
90
advantages of biomass and wood
cheap and readily available as a source of energy- if replaced, biomass can be a long term, sustainable energy source
91
disadvantages of solar power
no power at night or when it's cloudy
92
disadvantages of wind power
can cause noise and visual pollution, amount of electricity depends heavily on the weather
93
disadvantages of wave and tidal power
May be opposed by local or environmental groups
94
disadvantages of hydroelectric power
can cause flooding of surrounding communities and landscapes
95
disadvantages of biomass and wood
gives off carbon dioxide and sulfur dioxide when burned, biomass and wood are only renewable resources if crops and trees are replanted
96
greenhouse effect
infrared radiation emitted by the surface of the earth is absorbed by greenhouse gases in the atmosphere- this causes the atmosphere to warm up in a process called the greenhouse effect
97
what different fuse ratings are available?
1A, 3A, 5A and 13A
98
what is one watt equivalent to?
one joule per second
99
kilowatt-hour
the energy used by an appliance of power 1kW used for 1 hour- it's the unit of energy used by electrical suppliers and is used on electricity bills
100
what is the kilowatt-hour a unit of?
energy- not power
101
examples of energy-saving devices?
compact fluorescent bulbs, motion-activated lights, home insulation and standby detection devices
102
payback time
the number of years it takes it get back the cost of an energy-saving method
103
how do you calculate payback time?
initial cost divided by annual saving
104
what does installing double glazing do?
it provides better soundproofing and increases the saleability of a home
105
what are all electrical appliances marked with?
a power rating in watts or kilowatts
106
what does the cell do in a circuit?
it gives energy to the electrons so that they can transfer energy to the components of the circuit- the chemical energy in the cell is converted to electrical energy of the electrons
107
how does the voltage add up in a series circuit?
the voltage across individual components adds up to the voltage across the power supply
108
how does the voltage add up in parallel circuits?
the voltage across each component is the same as the voltage across the power supply
109
what is the potential difference of 1 volt?
1 joule of energy per coulomb of charge
