November test Weeks 6-10 Flashcards
how is electricity produced (generally)
- 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
Fossil fuels advantages
- cheap and reliable (does not rely on weather)
- well developed systems to harness energy
Fossil fuels disadvantages
- contains high levels of carbon and contributes to global warming
- non-renewable and unsustainable
- accidents could occur to add to pollution and environmental contamination
What are fossil fuels
- 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)
What is shale gas?
- 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
Why is fracking controversial?
- fractures rock to release gas -> causes earth tremors that damage building foundations
What is nuclear power?
- 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
Advantages of nuclear power
- 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
Disadvantages of nuclear power
- 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
what is renewable energy?
Natural sources of energy that are non-finite and can be quickly replenished (eg. wind, biomass, solar)
What is wind power?
energy from wind turns propeller-like blades on rotor (connected to generator)
Advantages of wind power
- cost effective
- clean source of energy
- sustianable and renewable
Disadvantages of wind power
- 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
what is tidal power?
- movement of water (tide) turn underwater turbines which drive the generators
Advantages of tidal power
- predictable
- renewable
- clean source of energy
Disadvantages of tidal power
- expensive to set up and maintain
How do solar panels create energy
- abosorb light into photovoltaic cells which is converted into electricity
Advantages of solar panels
- renewable
- clean
- energy can be collected on sunny or cloudy days
Disadvantages of solar panels
- low energy generated during winter months (daylight hours are shorter)
What is biomass and how is it used?
- 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
Advantages of biomass
- renewable
- carbon neutral
Disadvantages of biomass
- risk of deforestation if trees are not planted
- CO2 emissions are made (global warming)
What is hydroelectric power?
- turbine converts kinetic energy of falling water into mechanical energy and generator turns it into electricity
- eg. dams
Advantages of hydroelectric power
- renewable
- reliable
- clean
- regulated according to demand (can be switched on and off)
Disadvantages of hydroelectric power
- cost and environmental pollution of building dam is high (CO2 produced when building)
- impacts on surrounding water flow
- affects ecosystems
How is kinetic energy stored?
- using kinetic pumped storage systems
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
How do batteries (portable energy storage systems) work
- contains electro-chemicals that react with each other to produce an electric voltage
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)
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
Why should batteries be disposed of properly?
- contains toxic chemicals
- can contaminate the soil and water if left at landfill
- dispose at recycling centre
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
What is graphene?
- a single layer of carbon atoms bound togther in a hexagonal lattice
What are graphene’s properties?
- thinnest known material
- strong, light, conductive
- used in sports equipment, cooling technology in mobile phones
What is metal foam?
- metal containing gas filled pores
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
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
Why are LCDs developed?
- high consumer demand for wearable and large displays, higher definition, longer battery life for portable devices
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)
What are nanomaterials?
- materials or substances made at a very small scale
- less than 100 nanometres in size
- adds properties to products
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
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.
What is titanium?
- a metal found in the earth’s crust
What are the properties of titanium?
- high strength
- lightweight
- resists corrosion
- does not react with human tissue
- used to make artificial joints
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
What is polymorph used for?
- making ergonomic handles
- prototype mechanical parts
- mouldings
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
What is an example of SMAs?
- Nitinol used in dentistry for braces
- Nitinol mesh used for expandable stents in vascular surgery
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
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
What are some disadavantages of composite materials?
- hard to separate and recycle
- can be expensive
- resins/ adhesives can cause risks
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
What are photochromic materials?
- change colour when exposed to different UV levels
- pigments degrade from over exposure to UV light
- used in glasses
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
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
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
What is Gore-Tex?
- breathable and waterproof
- allows vapour to escape but pores are too small for water
- used for outdoor clothing
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
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 synthetic fibre
- cut, puncture, ballistic resistant/ bullet proof
- make body armour, bullet proof vests, reinforce tyres, add strength and durability to sports equipment
How is Kevlar so bullet proof
- projectile hits Kelvar -> fibres “catch” it
- abosorbs and dissipates its energy
What are technical textiles used to make?
- protective clothing in sports, medical, hazardous and industrial enviornments
- provides chemical protection
- flame resistance
- cut resistance
What are microfibres?
- synthetic fibres less than one denier thick
- can be micro-encapuslated
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
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
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
What does an input device do in a electrical circuit?
- sense that something has changed eg. motion, heat, light, moisture etc
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
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
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
Input, process or output?
What does a switch do?
- switches circuit on or off
- used in lighting, control panels and power switches
Input, process or output?
What does a thermistor do?
- detects change in temperature
- as temperature increases resistance decreases
- used in household appliances and vehicles
Input, process or output?
What does a resistor do?
- limit the flow of the current
- protects some components from being overloaded
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
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
What can microcontrollers be programmed to do?
- decision making with timing and counting functions
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
What is an open loop system?
- the output does not directly affect the input
- eg. toaster
What is a closed loop system?
- output does directly affect the input
- eg. house thermostat
What is polarity?
- have positive and negative connections
- must be connected the right way around a circuit otherwise they will not work
What is a buzzer?
- gives a sound output
- electromagnetic wires turn circuit on and off to create buzz
What is a lamp?
- uses electricity to produce light of varying levels
What is a light emitting diode? (LED)
- low power light used in power indicators and lamps
- long lasting
What is a speaker?
- translate electrical signal into audible sound
What is linear motion
- movement in one direction along a straight line
What is reciprocating motion?
- repetitive up and down or back and forth linear motion
What is rotary motion?
- movement on or around an axis
- eg. wheel
what is oscillating motion?
- movement backwards and forwards along a curved path
- e.g swing
What does a typical lever consist of
- fulcrum: a pivot point around which a lever turns
- effort: an input force
- load: an output force
how to calculate mechanical advantage
MA = load/ effort
How to calcualte how much does it need to balance forces
force A x distance A = force B x distance B
What is a first order lever
- fulcrum is in the middle of effort and load
- eg. pliers
What is a second order lever?
- load is in the middle of the effort and fulcrum
- eg. wheelbarrow
What is a third order lever?
- effort is in the middle of fulcrum and load
- eg. tweezers
What is a reverse motion linkage?
- input & output move in opposite directions
- eg. clothes dryer
- Z shape
what is a push pull linkage?
- maintains direction of input to output (travels in same direction)
- eg. windscreen wipers on cars
What is a bell crank linkage?
- changes the direction of input motion 90 degrees
- changes horizontal motion into vertical motion (vice versa)
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
How does a circular cam or eccentric cam move?
- steady rise and fall
how does a pear cam move?
- rapid rise and fall followed by long dwell (rest)
How does a snail cam move?
- steady rise and sudden drop
- only turns in one direction otherwise it would jam
Flat follower advantages and disadvantages
- greater load carrying capabilities
- increased friction
- less accurate
Knife edge follower advantages and disadvantages
- greater accuracy
- wears quickly
- large side thrust
Roller follower advantages and disadvantages
- reduced friction
- runs at high speed
- more complex
- higher cost
What are gears?
- toothed wheels that mesh to transfer motion from one part of a machine to another
What is a gear train
- two are more gears meshed together
What is torque?
- force that causes rotation
What can gears change
- position of the movement
- direction of rotation
- speed of rotation
What does a drive gear do?
- turns the driven gear
- gears turn in opposite directions
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
How to calculate gear ratio?
gear ratio = number of teeth on driven gear/ number of teeth on drive gear (no units)
How to calculate velocity ratio
- rotations of the drive gear/ rotations of driven gear
- velocity ratio = gear ratio
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
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**
What is a drive belt?
- loop of flexible rubber
Label a diagram of a cam
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
