November test Weeks 6-10 Flashcards

1
Q

how is electricity produced (generally)

A
  • involves rotating a turbine which turns a generator
  • fossil fuels burned to create heat to superheat the water
  • steam turns turbine (linked to generator) to produce electricity
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2
Q

Fossil fuels advantages

A
  • cheap and reliable (does not rely on weather)
  • well developed systems to harness energy
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3
Q

Fossil fuels disadvantages

A
  • contains high levels of carbon and contributes to global warming
  • non-renewable and unsustainable
  • accidents could occur to add to pollution and environmental contamination
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4
Q

What are fossil fuels

A
  • finite resources
  • gas -> electricity in the UK, heating and cooking
  • coal -> burned to create energy
  • oil -> create plastics or fuel
  • burning these fuels produces large amounts of CO2 (climate change)
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5
Q

What is shale gas?

A
  • a natural gas trapped in the earth’s crust
  • fracking: process to release gas from shale
  • sends a high pressure mixture of water, sand, chemicals into the rock to release gas
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6
Q

Why is fracking controversial?

A
  • fractures rock to release gas -> causes earth tremors that damage building foundations
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7
Q

What is nuclear power?

A
  • produces energy by fission (splitting uranium atoms in a nuclear reactor)
  • same heat/steam/turbine process as coal power station except heat is made with nuclear fission
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8
Q

Advantages of nuclear power

A
  • no need for a large amount of space to generate electricity
  • does not produce CO2 or contribute to global warming
  • reliable (not dependant on weather)
  • low volume of waste produced
  • reduces demand for finite resources
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9
Q

Disadvantages of nuclear power

A
  • risk of nuclear accidents
  • disposal of nuclear waste (expensive), takes a long time to decay
  • high levels of security of needed (terrorism)
  • decommissioning nuclear plants safely-> costly (high risk of contamination)
  • construction, operation and decommissioning nuclear power plant may harm the environment
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10
Q

what is renewable energy?

A

Natural sources of energy that are non-finite and can be quickly replenished (eg. wind, biomass, solar)

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11
Q

What is wind power?

A

energy from wind turns propeller-like blades on rotor (connected to generator)

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12
Q

Advantages of wind power

A
  • cost effective
  • clean source of energy
  • sustianable and renewable
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13
Q

Disadvantages of wind power

A
  • unpredictable (weather based)
  • can be noisy
  • affect visual appearance of landscape
  • distance from wind sites (location on hilltops or out at sea) = high costs to connect to national grid
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14
Q

what is tidal power?

A
  • movement of water (tide) turn underwater turbines which drive the generators
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15
Q

Advantages of tidal power

A
  • predictable
  • renewable
  • clean source of energy
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16
Q

Disadvantages of tidal power

A
  • expensive to set up and maintain
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17
Q

How do solar panels create energy

A
  • abosorb light into photovoltaic cells which is converted into electricity
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18
Q

Advantages of solar panels

A
  • renewable
  • clean
  • energy can be collected on sunny or cloudy days
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19
Q

Disadvantages of solar panels

A
  • low energy generated during winter months (daylight hours are shorter)
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20
Q

What is biomass and how is it used?

A
  • produced from organic matter
  • energy extracted by burning/ anaerobic digestion (no air, bacteria breaks down organic matter and produces methane)
  • methane can be used to heat homes or fuel
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21
Q

Advantages of biomass

A
  • renewable
  • carbon neutral
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22
Q

Disadvantages of biomass

A
  • risk of deforestation if trees are not planted
  • CO2 emissions are made (global warming)
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23
Q

What is hydroelectric power?

A
  • turbine converts kinetic energy of falling water into mechanical energy and generator turns it into electricity
  • eg. dams
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24
Q

Advantages of hydroelectric power

A
  • renewable
  • reliable
  • clean
  • regulated according to demand (can be switched on and off)
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25
Disadvantages of hydroelectric power
- cost and environmental pollution of building dam is high (CO2 produced when building) - impacts on surrounding water flow - affects ecosystems
26
How is kinetic energy stored?
- using kinetic pumped storage systems
27
How do kinetic pumped storage systems work?
- holds water in upper reservoir - high electricity demand = dam opens and water released into lower reservoir to drive turbines -> electricity - night (lower electricty demand) water is pumped back up & cycle continues
28
How do batteries (portable energy storage systems) work
- contains electro-chemicals that react with each other to produce an electric voltage
29
Describe alkaline batteries
- high energy capacity - long shelf life - once chemical reactants are used = no longer usable - power output decreases over time - 1.5 V (except PP3, which is 9 V)
30
Describe rechargable batteries
- can be charged many times - will drain whether if you use it or not - power output remains constant until it runs flat - 1.2 V per cell
31
Why should batteries be disposed of properly?
- contains toxic chemicals - can contaminate the soil and water if left at landfill - dispose at recycling centre
32
What is a modern material?
- discovered or developed since WW2 (1945) - materials specifically developed with enhanced properties, through the invention of new or improved processes
33
What is graphene?
- a single layer of carbon atoms bound togther in a hexagonal lattice
34
What are graphene's properties?
- thinnest known material - strong, light, conductive - used in sports equipment, cooling technology in mobile phones
35
What is metal foam?
- metal containing gas filled pores
36
What are the properties of metal foam?
- good stiffness to weight ratio - good thermal insulation - good sound absorption - used for weight saving and impact absorbing structures in vehicles
37
What are liquid crystal displays? (LCD)
- matrix of pixels that display an image on the screen - backlight provides light to individual pixels - varies red, blue, green light to make colour combinations
38
Why are LCDs developed?
- high consumer demand for wearable and large displays, higher definition, longer battery life for portable devices
39
What are coated metals?
- protects metal, reduces wear and tear (more durable) - unprotected ferrous metal is liable to rust - eg. galvanised (zinc coated) steel, Teflon (non-stick), anodising (coloured aluminium)
40
What are nanomaterials?
- materials or substances made at a very small scale - less than 100 nanometres in size - adds properties to products
41
What properties can nanomaterials add?
- tensile strength - rigidity - produce more lightweight products - used in electronics + medicine - make textiles resistant to bacteria, super hydrophobic, repel dirt, neutralise bad odours
42
What are smart materials?
- responsive materials that are designed to react to external stimuli. they can alter the functional or aesthetic properties in response to a changing environment.
43
What is titanium?
- a metal found in the earth's crust
44
What are the properties of titanium?
- high strength - lightweight - resists corrosion - does not react with human tissue - used to make artificial joints
45
What is polymorph?
- polymer that can be shaped and reshaped many times - when warmed to 62C beomes flexible and easy to mold - as it cools it becomes stiff and strong
46
What is polymorph used for?
- making ergonomic handles - prototype mechanical parts - mouldings
47
What is a shape memory alloy? (SMA)
- group of materials that revert back to their original shape after being deformed by heat or another external stimulus
48
What is an example of SMAs?
- Nitinol used in dentistry for braces - Nitinol mesh used for expandable stents in vascular surgery
49
What is a quantum tunnelling composite? (QTC)
- flexible polymer with tiny metal particles embedded into it - when squeezed current of electrons flows between neighbouring particles - electrons jumping across a gap from one conducting material to another is known as quantum tunnelling - used in microswitches, touch sensitive pads
50
What is a composite material?
- composed of at least two materials - when combined the properties are *superior* to those of the individual components - eg. fire/ corrosion resistance, better strength to weight ratio, better tensile strength
51
What are some disadavantages of composite materials?
- hard to separate and recycle - can be expensive - resins/ adhesives can cause risks
52
What are thermochromic materials?
- change colour at certain ranges of temperature (cold or hot activation) - can be incorportaed into inks and printed onto plastic - used in baby safety products, mugs
53
What are photochromic materials?
- change colour when exposed to different UV levels - pigments degrade from over exposure to UV light - used in glasses
54
What is glass reinforced plastic (GRP)?
- polyester material reinforced with the addition of glass fibre - combines thermosetting polyester resin and glass fibre matting - strong, lightweight - used in circuit boards, pond liner, kayaks - cheap but heavier than CFRP
55
What is carbon fibre reinforced plastic? (CFRP)
- thermoplastic reinforced with carbon fibres - produced by combining thermoplastic polymer resin with carbon fibre matting using a "lay up" process - high strength to weight ratio - rigid - used in sports equipment, aerospace engineering
56
What are technical textiles?
- made from a combination of natural and synthetic fibres and filaments - can be coated, laminated or impregnated to improve the properties and performance of the item - used in geotextiles, argotextiles
57
What is Gore-Tex?
- breathable and waterproof - allows vapour to escape but pores are too small for water - used for outdoor clothing
58
What is Kevlar and what is it made of?
- plastic fibre with high tensile strength - made of modified polyamide fibres (from class of fibres called aramids) - polyamide molecules connect to form long chains - aligned parallel to each other inside the fibres acting as reinforcement
59
What are the properties of Kevlar and what is it used for?
- plastic fibre with high tensile strength - heat resistant, extremely hard- wearing - flexible and lightweight - cut, puncture, ballistic resistant/ bullet proof - make body armour, bullet proof vests, reinforce tyres, add strength and durability to sports equipment
60
How is Kevlar so bullet proof
- projectile hits Kelvar -> fibres "catch" it - abosorbs and dissipates its energy
61
What are technical textiles used to make?
- protective clothing in sports, medical, hazardous and industrial enviornments - provides chemical protection - flame resistance - cut resistance
62
What are microfibres?
- synthetic fibres less than one denier thick - can be micro-encapuslated
63
What is micro-encapsulation?
- packaging particles or droplets - can improve properties of microfibre as they can hold anti-microbial agents, insecticides, medicine etc - can release these with control
64
What are fire resistant fabrics?
- designed to withstand heat and resist burning - provides protection against heat without melting or dripping - eg when Nomex is exposed to heat the fibres thicken and absorb heat energy
65
What are conductive fabrics?
- made from, coated or blended with conductive materials - used for thermal heating or allowing electrical signals to pass through with little resistance - can have batteries, small lights, electronics embedded into them - used in sportsear to monitor vital statistics
66
What does an input device do in a electrical circuit?
- sense that something has changed eg. motion, heat, light, moisture etc
67
What does an process device do in a electrical circuit?
- manipulate/ notice the voltage/ signal from the input to control the output component, usually by switching it on or off
68
# Input, process or output? What does an LDR do?
- detects changes in light levels - resistance increases in dark and decreases in light - used in street lamps and security lights
69
# Input, process or output? What does a pressure sensor do?
- detects changes in pressure in gases or liquids - eg. detect leak in fuel system - used to detect weight - eg. detect a burgular has stepped on a mat
70
# Input, process or output? What does a switch do?
- switches circuit on or off - used in lighting, control panels and power switches
71
# Input, process or output? What does a thermistor do?
- detects change in temperature - as temperature increases resistance decreases - used in household appliances and vehicles
72
# Input, process or output? What does a resistor do?
- limit the flow of the current - protects some components from being overloaded
73
# Input, process or output? What does a microcontroller do?
- programmable component, can be programmed in a variety of programming languages or software that uses flowcharts for programming - tiny computer on a single chip - can perform the task of multiple ICs - used in electrical products such as washing machines
74
What are the advantages of using a microcontroller rather than multiple ICs?
- microcontroller is cheaper than multiple ICs - circuit can be made smaller - can be updated with software updates/ reprogrammed
75
What can microcontrollers be programmed to do?
- decision making with timing and counting functions
76
What are the symbols used for a flowchart
- start and stop: round rectangle - process: rectangle - decision (yes or no outcome): rhombus - arrow: indicates the flow of instructions
77
What is an open loop system?
- the output does not directly affect the input - eg. toaster
78
What is a closed loop system?
- output does directly affect the input - eg. house thermostat
79
What is polarity?
- have positive and negative connections - must be connected the right way around a circuit otherwise they will not work
80
What is a buzzer?
- gives a sound output - electromagnetic wires turn circuit on and off to create buzz
81
What is a lamp?
- uses electricity to produce light of varying levels
82
What is a light emitting diode? (LED)
- low power light used in power indicators and lamps - long lasting
83
What is a speaker?
- translate electrical signal into audible sound
84
What is linear motion
- movement in one direction along a straight line
85
What is reciprocating motion?
- repetitive up and down or back and forth linear motion
86
What is rotary motion?
- movement on or around an axis - eg. wheel
87
what is oscillating motion?
- movement backwards and forwards along a curved path - e.g swing
88
What does a typical lever consist of
- fulcrum: a pivot point around which a lever turns - effort: an input force - load: an output force
89
how to calculate mechanical advantage
MA = load/ effort
90
How to calcualte how much does it need to balance forces
force A x distance A = force B x distance B
91
What is a first order lever
- fulcrum is in the middle of effort and load - eg. pliers
92
What is a second order lever?
- load is in the middle of the effort and fulcrum - eg. wheelbarrow
93
What is a third order lever?
- effort is in the middle of fulcrum and load - eg. tweezers
94
What is a reverse motion linkage?
- input & output move in opposite directions - eg. clothes dryer - Z shape
95
what is a push pull linkage?
- maintains direction of input to output (travels in same direction) - eg. windscreen wipers on cars
96
What is a bell crank linkage?
- changes the direction of input motion 90 degrees - changes horizontal motion into vertical motion (vice versa)
97
What is a cam used for?
- used to change rotary motion into reciprocating motion using a follower - crank is used to rotate the shaft which rotates the cam and moves the follower up and down
98
How does a circular cam or eccentric cam move?
- steady rise and fall
99
how does a pear cam move?
- rapid rise and fall followed by long dwell (rest)
100
How does a snail cam move?
- steady rise and sudden drop - only turns in one direction otherwise it would jam
101
Flat follower advantages and disadvantages
- greater load carrying capabilities - increased friction - less accurate
102
Knife edge follower advantages and disadvantages
- greater accuracy - wears quickly - large side thrust
103
Roller follower advantages and disadvantages
- reduced friction - runs at high speed - more complex - higher cost
104
What are gears?
- toothed wheels that mesh to transfer motion from one part of a machine to another
105
What is a gear train
- two are more gears meshed together
106
What is torque?
- force that causes rotation
107
What can gears change
- position of the movement - direction of rotation - speed of rotation
108
What does a drive gear do?
- turns the driven gear - gears turn in opposite directions
109
What does an idler gear do?
- change the direction of rotation - drive and driven gear = same direction - size of idler gear does not affect rotation speed
110
How to calculate gear ratio?
gear ratio = number of teeth on driven gear/ number of teeth on drive gear (no units)
111
How to calculate velocity ratio
- rotations of the drive gear/ rotations of driven gear - velocity ratio = gear ratio
112
What do pulleys do?
- transmit rotary motion and force from input or drive shaft to the output or driven shaft - belts are made with reinforced rubber or high strength materials like Kevlar
113
Compare pulleys to gears
- gears **mesh directly** while pulleys need a **belt to connect** - meshed gears go in **opposite directions** whereas pulleys in a system move in the **same direction** - meshed gears have to be positioned **very precisely** (too close= high friction, too far = wear and fail quickly) - gears connected with chain need to be placed quite precisely, chains are made of **metal of fixed length** - pulley belts **have some flexibility so distance is not cruicial** - gears are used for **high torque** applications (allow for higher torque) - if gear becomes stuck **driver gear would break** - if pulley becomes stuck the** belt would slip off the pulley**
114
What is a drive belt?
- loop of flexible rubber
115
Label a diagram of a cam
116
How is MDF and chipboard made?
- wood processesd into chips or particles - particles are mixed with adhesive (foremaldehyde resin) - mixture is compressed into shape with rollers and heated to cure the adhesive - boards are trimmed to standard sizes