Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

la física > Electricity P1 > Flashcards

Electricity P1 Flashcards

1
Q

Define energy

A

The ability to do work, energy allows matter to move or cause change and makes things happen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Name 9 types of energy

A

Sound, kinetic, chemical, heat, light, elastic potential, gravitational potential, magnetic, nuclear

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Identify 4 ways to transfer energy

A

Mechanically (by a force doing work), electrically (work done by mpving charges), heating, radiation (light or sound)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How do energy transfers work?

A

In order to increase an energy store, it must be transferred between stores. When a system (object or group of objects) changes energy is transferred into or away from the system between different types of energy stores

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the law of conservation of energy?

A

Energy can be transferred usefully, stored or dissipated but never created or destroyed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Define work

A

To move an object with an applied force

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What must happen to move an object along a surface?

A

Frictional forces opposing the direction of motion must be overcome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Define friction

A

An opposing force to direction of movement when two surfaces are in contact

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Equation for work

A

Work = force x distance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What happens when an object is moved vertically?

A

Work is done against gravitational force and the objects gravitational potential increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What happens when an object is moved down?

A

It’s gravitational store decreases and the energy is equal to the work done by the force of gravity acting upon it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Equation for weight/force

A

Weight= mass x gravitational field strength =force

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Equation for work done

A

Work done = Force x distance = weight x height

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Equation for change in gravitational potential energy

A

Change in gravitational potential energy = mass x gravitational field strength x change in height

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Three uses of mechanical springs

A

To provide a force, to provide flexibility, to absorb energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Equation for force of a spring

A

Force = spring constant(N/m) x extension (in metres)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What happens when we stretch or compress a string?

A

They become deformed and we have had to put energy into doing this therefore the energy is now stored in the string in the form of elastic potential energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Equation for kinetic energy

A

0.5 x mass x velocity^2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Define energy efficiency

A

Getting as much useful energy output as possible from a device

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Define being efficient

A

Performing in the best possible way with the least waste of time or effort

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What happens to waste energy?

A

It is dissipated to the surroundings which become warmer. It becomes increasingly spread out and less useful

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Compare CLF bulbs and filament bulbs

A

CLF bulbs transfer less energy as heat compared to filament bulbs therefore they require less power

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Equation for efficiency

A

Efficiency = useful energy out divided by total energy supplied in x 100

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Equation for energy, power and time

A

Energy = power x time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Define powering a device

A

To supply a device with mechanical or electrical energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Define power

A

How quickly energy is used

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Define thermal conductivity

A

The rate at which energy is transferred through a material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Define infrared radiation

A

A type of electromagnetic wave which transfers heat energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Define a perfect black body

A

An object which absorbs all of the radiation which hits oyster and does not reflect/transmit any radiation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Name two factors affecting the specific heat capacity of a substance

A

Mass & type of substance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Equation for specific heat capacity

A

Change in energy required = mass x specific heat capacity x temperature change

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Define specific heat capacity

A

The amount of energy needed to change the temperature of 1kg of a substance by 1 degree Celsius

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Define u-value

A

Measures how effective a material is as an insulator, the lower it is the better the insulator

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Name 6 ways of insulating your home

A

Loft insulation, cavity wall insulation, double glazing, draught proofing, carpets, radiators, have thick walls made from a material with a low thermal conductivity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Equation for payback time

A

Payback time = cost of installation divided by savings per year

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Name 8 energy sources

A

Tidal, biomass, geothermal, nuclear, wind, hydroelectric, solar, fossil fuels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

How does a fossil fuelled power plant work?

A

Burns coal, produces steam, turns the turbine, generates energy in the generator, energy is transformed in the transformer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

How does hydroelectric power work?

A

Water is held behind a dam, rainwater is caught and runs through pipes and passes through a turbine, turbine is connected to generator to produce electricity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Name 6 advantages of hydroelectric power

A

Reliable except in times of drought, water can be stored until demand is high, no pollution, constant rate of electricity generation, lasts many decades, no fuel costs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

Name 5 disadvantages of hydroelectric power

A

Expensive set up, people have to leave their homes, causes flooding of the valley (rotting vegetation releases methane and carbon dioxide), must operate for decades before profitable, habitats destroyed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

How does geothermal energy work?

A

Several rocks contain radioactive substances which release heat energy whilst decaying, hot rocks can heat water which rises to the surface as steam which can be used to turn turbines connected to generators

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

Name 5 advantages of geothermal energy

A

Renewable, no fuel costs, no pollution, reliable, free resource

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

Name 4 disadvantages of geothermal power

A

Only possible in volcanic areas where hot rocks lie close to the surface, harmful gases released, most sites far from populations, high installation costs compared to amount of energy it produces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

How does wind power work?

A

Wind farms set up in exposed areas like on moors and wind over the blades turns the turbine and therefore the generator inside it which produces electricity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

Name 5 advantages of wind power

A

Wind is free, no pollution, used in remote locations, land under the turbine can still be used, no permanent damage to landscape

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

Name 5 disadvantages of wind power

A

Unreliable (only produce electricity 70-85% of time because they stop when the wind stops are is too strong), noisy, ugly, huge wind farms needed to supply a town or city with electricity (1500 turbines to replace one coal fired power station), initial costs are high

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

How does solar power work?

A

Generates electric currents directly from sunlight. Focusing sunlight generates heat to boil water and steam turns a turbine connected to a generator

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

Name 4 advantages of solar power

A

Once set up the energy is free, no pollution, used in remote locations, renewable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

Name 4 disadvantages of solar power

A

Initial set up is expensive, only works during the day and when its sunny, require large amounts of land

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

How does wave energy work?

A

Lots of small wave powered turbines located around the coast, moving turbines are connected to a generator

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

Name 3 advantages of wave power

A

No pollution, minimal running costs, no fuel costs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

Name 4 disadvantages of wave power

A

Cost up set up is high, disrupts sea life, unreliable since waves die out when wind drops, never likely to provide energy on a large scale

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

Name 4 advantages of fossil fuels

A

Produces a lot of energy, power plants always have fuel in stock to respond quickly to changes in demand, safer, cheaper running costs than some other energy resources

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

Name 6 disadvantages of fossil fuels

A

Non-renewable and running out, greenhouse gases released leading to global warming, sulphur dioxide released which causes acid rain, global dimming caused, high cost to set up power plants, coal mining makes a mess of the landscape

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

How does nuclear power work?

A

Originates from the splitting of uranium atoms which generates heat and produces steam to turn a turbine connected to a generator

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

Name 3 advantages of nuclear power

A

Reliable generation of electricity, no carbon dioxide or sulphur dioxide produced, meets basic deman

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

Name 3 disadvantages of nuclear power

A

Radioactive materials are dangerous, radioactive waste products need to be disposed of, expensive to decommission

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

Define electric current

A

Flow of electric charge (in coulombs). Current can only flow around a complete circuit if there’s potential difference. Measured in amperes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

What happens when charge builds up?

A

It spreads out and takes the route to the ground

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

Name the 2 types of circuit

A

Series and parallel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

What do amps measure?

A

The amount of electric charge flowing each second

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

Equation for current

A

Current = charge divided by time (seconds)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

How do electrons move through a circuit?

A

From the negative terminal of the battery to the positive terminal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

When can a metal object hold charge?

A

When it is insulated from the ground

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

What happens when two negatively charged metal objects are brought into contact?

A

Electrons transfer from the negative to the positive object

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
66
Q

Define resistance

A

How easy it is for current to get through a wire

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
67
Q

What are resistors used for?

A

Slowing down the current

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
68
Q

Name 5 factors affecting resistance

A

Thickness of wire, length of wire, material, temperature, whether components are in series or parallel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
69
Q

What is the relationship between thickness of wire and resistance?

A

The thicker the wire, the less resistance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
70
Q

What is the relationship between temperature and resistance?

A

Heating a wire increases its resistance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
71
Q

Define ohms law

A

The current through a conductor at constant temperature is directly proportional to the voltage across two points

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
72
Q

Relationship between resistance, voltage and current

A

Resistance = voltage divided by current

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
73
Q

Define an ohmic resistor

A

A wire in which the current and voltage are directly proportional

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
74
Q

What is the relationship between length of wire and resistance?

A

The longer the wire, the higher the resistance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
75
Q

Is resistance higher in series or parallel and why?

A

Series because there are more pathways for current to flow in parallel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
76
Q

Define voltage

A

The amount of push in a circuit, the driving force of the circuit. Energy transferred per charge pressent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
77
Q

Describe current in a series circuit

A

Current is the same everywhere. The size of the current is determined by total potential difference of cells and total resistance of the circuit

78
Q

Describe voltage in a series circuit

A

There is a higher voltage when there are more cells provided that they are connected the same way. The total potential difference of the supply is shared between components. Potential differences around a series circuit always add up to the source potential difference

79
Q

Describe resistance in a series circuit

A

Total resistance of two components is the sum of their resistances because by adding a resistor in series the two resistors have to share the total potential difference. The pd and current through each resistor is lower and current is the same everywhere but is reduced when a resistor is added which means total resistance increases

80
Q

Describe current in a parallel circuit

A

The current along the branches is equal to that flowing around the circuit

81
Q

Describe voltage in a parallel circuit

A

Voltage is the same between components, full source voltage

82
Q

Relationship between resistance and light intensity

A

The resistance of a light dependent resistor increases as the light intensity decreases

83
Q

Define alternating current

A

Current that repeatedly changes direction, caused by the charge carriers moving one way and then the other, frequency defines how often direction changes

84
Q

Define direct current

A

Current which flows in one direction only

85
Q

How is alternating current produced and used?

A

Produced by generators and used in mains electricity that is distributed to our homes

86
Q

Can alternating current be transferred efficiently over large distances?

A

Yes, with the help of transformers

87
Q

How is direct current produced and used?

A

Produced by cells and batteries, created by a direct potential difference and use sod electronic circuits such as those in computers

88
Q

Can direct current be transferred efficiently over large distances?

A

No

89
Q

What would happen to an AC waveform on an oscilloscope screen if the time base is switched off?

A

A vertical line would appear

90
Q

Give two reasons alternating currents are dangerous

A

Were used to electrocute animals, were used to electrocute people on the death penalty

91
Q

Give three positives of alternating current

A

Half the price of direct, can be transmitted over great distances, efficient way to ‘step down’ voltage for common uses

92
Q

Give three negatives of direct current

A

Expensive at $1million, no efficient way to ‘step down’ voltage for common uses, cannot be transmitted over great distances

93
Q

Give one positive of direct current

A

Worked well for powering light bulbs

94
Q

What does the live wire do?

A

Carries the alternating current from the supply at 230V

95
Q

Colour of live wire

A

Brown

96
Q

What does the neutral wire do?

A

Completes the circuit at 0V and carries away current

97
Q

Colour of neutral wire

A

Blue

98
Q

What does the earth wire do?

A

Stops the device becoming ‘live’, acts as a safety wire and protects the wiring, only carries current when there is a fault, it is also at 0V

99
Q

Colour of earth wire

A

Green and yellow

100
Q

Why are wires made of copper?

A

It is a good conductor which can be drawn out into long thin wires

101
Q

Why are wires surrounded by plastic?

A

It is flexible and a good insulator

102
Q

Why are the pins in a plug made of brass?

A

It is a good conductor

103
Q

What happens if too much current passes through a fuse wire?

A

The fuse wire melts which cuts off the live wire

104
Q

What is a nanowatt?

A

0.000000001W (8 zeros after decimal point)

105
Q

What is a milliwatt?

A

0.001W (2 zeros after decimal point)

106
Q

What is a kilowatt?

A

1000W

107
Q

What is the equation for power, current and resistance?

A

Power = Current^2 x resistance

108
Q

What is the equation for energy, coulomb, time?

A

Current = Coulomb divided by time

109
Q

What is the equivalent in electrons to 1 coulomb?

A

6.2 x 10^18 electrons

110
Q

What is the equation linking energy transferred, potential difference and charge?

A

Energy transferred = potential difference (V) x charge (Q)

111
Q

Identify 5 ways energy gets from the power station to your home?

A

National grid, transformer, step down, step up, pylons

112
Q

What is the national grid?

A

A system of cable and transformer connecting power stations to consumers. It transfers electrical power from any power station on the grid to any homes or industry etc on the grid

113
Q

What are pylons?

A

Tall structures which carry electricity above the ground through aluminium cables

114
Q

Give three advantages of overhead cables

A

Relatively cheap to link between tall towers, easy access to maintain, open to air cooling

115
Q

Give three disadvantages of overhead cables

A

Ruin landscapes, vulnerable to weather, cut across large areas of land

116
Q

Give four disadvantages of underground cables

A

Expensive, harder maintenance, hard to cool, need to mark where they are

117
Q

What is the equation for primary and secondary voltage and number of turns?

A

Primary voltage divided by secondary voltage = primary number of turns divided by secondary number of turns

118
Q

Why does the matte back metal case of a stove improve rate of energy transfer?

A

Black is a good emitter. Matte surfaces are better emitters than glossy surfaces

119
Q

Give 2 environmental advantages of using a wood burning stove to heat a home rather than heaters which use electricity from fossil fuels

A

Fossil fuels release sulphur dioxide which causes acid rain, wood is a carbon neutral

120
Q

How does a cavity wall reduce unwanted energy transfers?

A

The cavity wall insulation, the clock and the brick have a low thermal conductivities so less energy is transferred by conduction. The wall is thick because it has three layers

121
Q

How are different energy stores changed by a boiler?

A

Chemical energy store of fuel decreases. Thermal energy store of the water increases. Thermal energy store of the air increases

122
Q

What is the equivalent in joules to one megajoule?

A

1MJ = 1000000J

123
Q

Equation for power, energy, time

A

Power = energy divided by time

124
Q

Equation for power, current and resistance

A

Power = current^2 x resistance

125
Q

Equation for charge, current and time

A

Charge = current x time

126
Q

How do the readings change on an ammeter and voltmeter in a series circuit with a LDR and fixed resistor when environmental conditions change?

A

When light intensity increases, the resistance of an LDR decreases, overall resistance of the circuit decreases, potential difference across total resistance remains unchanged, current in ammeter increases, potential difference across fixed resistor increases and PD across LDR decreases, reading on the voltmeter decreases. Potential difference is shared between components in series, the lower the resistance of the LDR the smaller the share of the potential difference, trading on the voltmeter decreases

127
Q

Identify 8 energy stores

A

Thermal, kinetic, elastic potential, gravitational potential, magnetic, electrostatic, nuclear, chemical

128
Q

Give an example of water being transferred by heating

A

You could think of the kettle’s heating element and the water as a two object system. Energy is transferred electrically to the thermal energy store of the kettle’s heating element which transfers energy by heating to the water’s thermal energy store

129
Q

In what two ways can work be done?

A

When current flows work Is done against resistance in a circuit, when a force moves an object

130
Q

What happens in terms of energy when a person throws a ball?

A

The initial force exerted by a person to throw a ball upwards does work, it causes an energy transfer from the chemical energy store of the person’s arm to the kinetic energy store of the ball and arm

131
Q

What happens in terms of energy when a car brakes?

A

The friction between a car’s brakes and wheels does work as the car slows down which causes an energy transfer from the wheels’ kinetic energy store to the thermal energy store of the surroundings

132
Q

What happens in terms of energy in a collision between a car and a stationary object?

A

The normal contact force between the car and the object does work, it causes energy to be transferred from the car’s kinetic energy store to other energy stores. Some energy may be transferred away by sound waves

133
Q

How do falling objects transfer energy?

A

When something is dropped from a height it’s accelerated by gravity, the gravitational force does work. As it falls energy from the object’s gravitational potential energy store is transferred to its kinetic energy store. For a falling object when there’s no air resistance energy lost from the GPE store is equal to energy gained in the kinetic energy store

134
Q

What does air resistance do?

A

Acts against all falling objects, causes some energy to be transferred to other energy stores e.g thermal energy stores of the object and surroundings

135
Q

How does energy in an object’s kinetic energy store change?

A

Energy is transferred to this store when a moving object speeds up and is transferred away from this store when the object slows down

136
Q

What does energy in the kinetic energy store depend on?

A

The greater its mass and the faster the object is travelling, the more energy in its kinetic energy store

137
Q

What materials can store a lot of energy?

A

Materials that need to gain a lot of energy in their energy stores to warm up but also transfer loads of energy when they cool down again

138
Q

How do you investigate specific heat capacity of a solid material? 10 points

A

Get a block of the substance with two holes in it (one for the heater and thermometer), measure mass of block, wrap in an insulating layer like thick layer of newspaper to reduce energy transferred to surroundings, measure initial temperature of the block, set potential difference of power supply to 10V, turn on power supply and start a stopwatch, when you turn on the power supply the current does work on the heater and transfers energy electrically from the power supply to the heaters thermal energy store, this energy is transferred to the materials thermal energy store by heating which causes temperature increase, measure temperature as block heats up using thermometer every minute and keep an eye on ammeter because the current should not change, after collecting 10 readings turn off the power supply

139
Q

What 5 calculations do you need to do after heating up the block in order to work out its specific heat capacity?

A

Calculate power supplied to heater using potential difference x current, use this to calculate how much energy has been transferred to the heater by timesing power by time (seconds), plot graph of energy transferred to thermal energy store of block against temperature, find gradient of the straight part of the graph, to get specific heat capacity of the material do 1 divided by (gradient x mass of block)

140
Q

What is a powerful machine?

A

One which transfers a lot of energy in a short space of time

141
Q

What is conduction?

A

The process where vibrating particles transfer energy to neighbouring particles.

142
Q

Describe what happens in conduction in 7 steps

A

Energy transferred to an object by heating is transferred to the thermal store of the object, this energy is shared across the kinetic energy store of the particles in the object, the particles in the part of the object vibrate more and collide with eachother , this causes energy to be transferred between particles’ kinetic energy stores, this process continues throughout the object until energy is transferred to the other side of the object, then it is transferred to the thermal energy store of its surroundings

143
Q

What is convection?

A

Energetic particles move away from hotter to cooler regions

144
Q

Describe what happens in convection in 5 steps

A

Energy is transferred by heating to the thermal store of a liquid or gas, energy is shared across the kinetic energy stores of a gas or liquid’s particles, when liquids or gases are heated particles move faster than in solids and the space between individual particles increases as the particles are able to move, this causes density of a region being heated to decrease, the warmer and less dense region rises above the denser cooler regions as liquids and gases flow so energetic particles move away from hotter to cooler regions

145
Q

How can you reduce the friction between two objects’ surfaces being rubbed together?

A

Use lubricants which are usually liquids like oil so can flow easily between objects and coat them

146
Q

What do frictional forces do?

A

Cause some energy in a system to be dissipated

147
Q

How does cavity wall insulation work?

A

Cavity walls are made up of an inner and outer wall with an air gap in the middle which reduces the amount of energy transferred by conduction through the walls. Cavity wall insulation fills the air gap with foam to reduce energy transfer by convection in the wall cavity

148
Q

How does loft insulation work?

A

Can be laid out across the loft floor and ceiling, fibreglass wool is often used which is a good insulator as it has lots of pockets of trapped air. Loft insulation reduces energy loss by conduction and helps prevent convection currents from being created

149
Q

What are convection currents?

A

A cycle where air particles are constantly being heated, rising, cooling then sinking

150
Q

How do double glazed windows work?

A

Have an air gap between two sheets of windows to reduce energy transfer by conduction through windows

151
Q

How do draught excluders work?

A

Put around doors and windows to reduce energy transfer by convection

152
Q

How are electric heaters 100% efficient?

A

All the energy in the electrostatic energy store is transferred to useful thermal energy stores

153
Q

Ultimately, where does all energy end up transferred to?

A

Thermal energy stores

154
Q

Identify 2 ways transport uses non renewable energy resources

A

Petrol and diesel powered vehicles use fuel created from oil, coal is used in some old fashioned steam trains to boil water to produce steam

155
Q

Identify a way transport uses renewable energy resources

A

Some vehicles run on pure biofuels

156
Q

Identify 3 ways heating uses non renewable energy resources

A

Natural gas is used to heat water in homes which is pumped into radiators, coal is burnt in fireplaces, electric heaters use electricity generated from non renewables

157
Q

Identify 3 ways heating uses renewable energy resources

A

Geothermal (or ground source) heat pumps use geothermal energy resources to heat buildings, solar water heaters use the sun to heat water which is then pumped into radiators in the building, burning bio fuel or using electricity from renewable resources can be used for heating

158
Q

What is solar energy used to generate energy for?

A

Only used to generate energy on a small scale like to charge batteries in calculators and watches or to power road signs and satellites

159
Q

How do tidal barrages work?

A

Tidal barrages are big dams that are built across river estuaries with turbines in them. As the tide comes in it fills up the estuary then water is allowed out through turbines at a controlled speed. Tides are produced by the gravitational pull of the sun and the moon

160
Q

Identify 5 advantages of tidal barrages

A

Tides are pretty reliable (happen twice a day without fail and always near predicted height), no pollution, no fuel costs, minimal running costs, potential for generating a significant amount of energy

161
Q

Identify 6 disadvantages of tidal barrages

A

Moderately high initial costs, alter habitat of wildlife, prevent free access by boats, spoil view, height of tide is variable so lower tides provide significantly less energy, don’t work when water level is the same on either side of the barrage which happens four times a day

162
Q

What are biofuels?

A

Renewable energy resources created from plant products or animal dung which can be solid, liquid or gas and can be burnt to produce electricity or run cars in the same way as fossil fuels

163
Q

Identify 2 pros of biofuels

A

Carbon neutral if the amount of CO2 released by burning is equal to the amount absorbed by plants you grow to make the biofuel, fairly reliable as crops take a relatively short time to grow

164
Q

Identify 5 cons of biofuels

A

Cost to refine them so they are suitable for use is very high, growing crops specifically for biofuels will mean there isn’t enough space or water to meet the demands for food, large areas of forest have been cleared to make room to grow biofuels which results in loss of species habitats, the decay and burning of this vegetation increases carbon dioxide and methane emissions, cannot meet immediate energy demands

165
Q

How can acid rain be reduced?

A

Take sulphur out before burning fossil fuels

166
Q

What 3 things has the UKs move towards renewable resources been triggered by?

A

Burning fossil fuels is very damaging to the environment, non renewables will run out one day so we need to learn to get by with renewables before this happens, , pressure from other countries caused the government to set targets for using renewables which puts pressure on energy providers to build renewable energy power plants so they don’t lose business/money

167
Q

Why is it difficult to change to renewable resources?

A

Scientists do not have the power to make companies/governments change their behaviour, building new renewable power plants costs money which some people don’t want to pay for or can’t afford to, arguments over where to put new power plants, some energy resources not as reliable as traditional fossil fuels, research on improving reliability and cost of renewables takes time and money, making personal changes like solar panels can be expensive

168
Q

What is the size of current?

A

Rate of flow of charge

169
Q

How does resistance of filament lamps change?

A

When an electrical charge flows through a filament lamp it transfers some energy to the thermal energy store of the filament which is designed to heat up. Resistance increases with temperature so as current increases the filament lamp heats up more and resistance increases

170
Q

How does resistance of diodes change?

A

Resistance depends on direction of the current , they let current flow in one direction but have a very high resistance if the current is reversed

171
Q

What does an ammeter do?

A

Measures current in camps flowing through the test wire in amps, must always be placed in series with whatever you’re investigating

172
Q

What does a voltmeter do?

A

Measure potential difference across the test wire in volts, must always be placed in parallel around whatever you’re investigating

173
Q

How can you investigate length of wire’s effect on resistance? 6 steps

A

Attach crocodile clip to a test wire level with 0cm on a ruler, attach the second crocodile clip to the wire a certain distance from the first wire (e.g 10cm), close the switch on the circuit then record current through the wire and the pd across it, open switch then move crocodile clip another 10cm along wire, close the switch again and record new current and pd, keep repeating with different lengths then use your measurements of current and pd to calculate resistance for each length of wire

174
Q

What is an I-V characteristic?

A

A graph which shows how current through a component changes as the pd across it is increased. Linear components like ohmic conductors’ graphs are straight lines whereas non linear components like filament lamps have a curved line

175
Q

How can you experiment to find a component’s I-V characteristic? 5 steps

A

Set up a series circuit with a variable resistor, ammeter, battery and component with a voltmeter around it, vary the variable resistor to alter current flowing through the circuit and potential difference across the component, take several pairs of readings from ammeter and voltmeter to see how potential difference varies as current changes, repeat each reading 3 times to get an average pd at each current, swap over wires connected to the cell so direction of current is reversed

176
Q

What is a light dependant resistor?

A

A resistor that is dependent on the intensity of light. In bright light resistance falls but in darkness resistance is very high. Used in automatic night light, outdoor lighting and burglar detectors

177
Q

What is a thermistor?

A

A temperature dependant resistor. In hot conditions resistance drops and in cool conditions it increases so they make useful temperature detectors like electronic thermostats

178
Q

What are sensing circuits used for?

A

Turning on or increasing the power to components depending on the conditions they are in

179
Q

What is potential difference like in a sensing circuit with a thermistor and a fixed resistor with a fan around it?

A

Potential difference of the power supply is shared out between the thermistor and the loop made up of the fixed resistor and fan according to their resistances - the bigger a components resistance, the more of the potential difference it takes. As the heat of the room increases the thermistor’s resistance falls so it takes less potential difference and the fan goes faster

180
Q

What happens if you add a resistor into a parallel circuit?

A

The total resistance of two resistors is less than the resistance of the smallest of the two resistors. The current has more direction to flow in parallel to increases which means a decrease in current

181
Q

How do you investigate the effect of placing resistors in a series circuit? 8 steps

A

Find at least 4 identical resistors, build a circuit with one resistor a battery and ammeter, make a note of pd of battery, measure current through circuit using an ammeter and calculate resistance, add another resistor in series with the first, measure current through circuit and work out resistance, repeat until you’ve used all resistors, plot a graph of number of resistors against total resistance of circuit

182
Q

How do you investigate the effect of placing resistors in a parallel circuit? 8 steps

A

Find at least 4 identical resistors, build a circuit with one resistor a battery and ammeter, measure total current through circuit and calculate resistance using pd of the battery, add another resistor in parallel with the first, measure total current of circuit and calculate overall resistance of the circuit, repeat until you’ve used all resistors, plot a graph of number of resistors against total resistance of circuit

183
Q

Why does touching a live wire give you an electric shock?

A

Your body like the earth is at 0V so touching the live wire produces a large potential difference across your body and a current flows through you

184
Q

What happens if the link between the live wire and earth creates a low resistance path to earth?

A

A large current will flow which could result in a fire

185
Q

What does total energy transferred depend on?

A

How long the appliance is on for and its power. Energy transferred = power x time

186
Q

When is an appliance cheaper to run?

A

If they have a lower power rating because this means they use less energy in a given time

187
Q

What happens when an electrical charge goes through a change in potential difference?

A

Energy is transferred, energy is supplied to the charge at the power source to ‘raise’ it through a potential. The charge gives up this energy when it falls through any potential drop in components elsewhere in the circuit.

188
Q

Equation linking energy transferred, potential difference and charge flow

A

Energy transferred = Charge flow x potential difference. This means a battery with a bigger pd will supply more energy to the circuit for every coulomb of charge which flows round it because the charge is ‘raised up’ higher at the start

189
Q

Equation linking potential difference, power and current

A

Power = potential difference x current

190
Q

What does electricity production need to meet?

A

Electricity usage/demand which is highest when people get up in the morning or return from school/work. Power stations often run at well below their maximum power output so there’s spare capacity to cope with a high demand even if there’s an unexpected shut down of another site

191
Q

What do you need in order to transmit huge amounts of energy?

A

Either a high potential difference or high current but the problem with high current is that you lose loads of energy as the wires heat up and energy is transferred to the thermal energy store of the surroundings. It’s much cheaper to boost the pd up really high and keep the current fairly low (the national grids does this). For a given power, increasing pd decreases current which decreases energy lost by heating wires etc

192
Q

What does boosting the pd to 400,0000 to transmit power require?

A

Transformers as well as big pylons with huge insulators. Step up transformers step up potential difference at one end for efficient transmission then step down transformers bring it back down to safe usable levels at the other end

la física (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions