Unit 2- Energy, Materials, Systems and Devices

Fossil Fuels

Fossil fuels are a finite resource, meaning that they cannot be replaced once extracted from the ground. In 2015, 80 per cent of energy consumed in the world came from fossil fuels. In early 2018, the UK's dependence on fossil fuels was at a low of 77 per cent. Examples include: coal, natural gas and oil

Coal

This energy is created through the burning of coal, which is usually crushed first. The hot coal heats water, turning it into steam.The steam builds up to a very high pressure and this is used to spin a turbine.The turbine is connected to an electrical generatorwhich creates electricity.

Renewable Energy sources

Wind turbines, Solar energy, Tidal energy, Hydroelectric power, Biofuel, Nuclear power

There are a number of ways to produce and store mechanical power. Most mechanical power used in technological products is stored by using tension or compression

Kinetic Energy Stores

Kinetic energy is the energy involved in motion. Objects that are not in motion possess potential energy, which is converted in to kinetic energy when some force, such as gravity, acts on the object to set it in motion.

What is a modern material?

Traditional materials are those that have been in use for centuries, such as paper, wood,stone and metals. We have also developed modern materials, which can be used alongside them.

Examples of modern materials

Concrete, aluminium and steel are all commonly used modern materials, but more recent additions include materials that have changed the way we manufacture and use products.

Graphine is a single carbon layer material, which is hypothetically 100 times stronger than steel. It is hypothetical because we are yet to manufacture it in large enough quantities to prove this. In theory, it could provide body armour that is bulletproof, invisible and almost weightless.

Titanium is a modern metal and is used in sporting and medical applications, such as replacement hip joints and high-performance bicycles. It is an excellent material for these purposes as it has a high strength-to-weight ratio and is resistant to corrosion.

A smart material is one which reacts to an external stimulus or imput. this means that it can alter its function or aesthetic properties in responce to the changing environment. This group of materials can react to stimuli such as heat, pressure, moisture, stress, PH level, light (including UV) and electricity.

Thermochromic Pigments

Thermochromic pigments change colour when their temperature changes. The term ‘thermo’ relates to heat, and chroma means colour - so thermochromic pigments change colour when they are heated up. These pigments can be mixed with paint or polymersto give the materials the same colour-changing propertiesas the pigment. An example of this technology is seen on colour-changing mugs or bath items for children.

Photochromic Pigments

Photochromic pigments work in a similar way but 'photo' refers to light - so these pigments change their properties when exposed to UVlight. A well-known example would be glasses where the lenses are clear when worn inside a building, but become more like sunglasses when exposed to bright sunlight outside. The same technology has been used in windows to prevent rooms from getting too hot in warm weather

Working Properties

• strength - the ability of a material to withstand compression, tension and shear,e.g in woven fabrics cotton isn’t as strong as wool when pulled
• hardness - the ability to withstand impact without damage, eg pine is easier to dent with an impact than oak; therefore, oak is harder
• toughness - materials that are hard to break or snap are tough and can absorb shock, eg Kevlar in bulletproof vests is a very tough material
• malleability - being able to bend or shape easily would make a material easily malleable, eg sheet metal such as steel or silver is malleable and can be hammered into shape
• ductility - materials that can be stretched are ductile, eg pulling copper into wire shows it is ductile
• elasticity - the ability to be stretched and then return to its original shape, eg elastane in swimming costumes is a highly elastic material

Physical Properties

• absorbency - the ability to soak up moisture, light or heat, eg natural materials (such as cotton or paper) tend to be more absorbent than man-made materials (such as acrylic or polystyrene)
• density - how solid a material is. This is measured by dividing mass (grams) by volume (cm³), eg lead is a dense material
• fusibility - the ability of a material to be heated and joined to another material when cooled, eg webbing is fusible and can be ironed onto fabrics
• electrical conductivity - the ability to conduct electricity, eg copper is a good conductor of electricity
• thermal conductivity - the ability to conduct heat, eg steel is a good heat conductor, whereas pine is not

Composite materials consists of two or more materials with different properties.They are combined to produce a material with improved properties. Most composite materials have two components:

• the renforcement
• the matrix, which binds the reinforcement together

It is often possible to separate the reinforcement from the matrix by physical processes. For example, reinforced concrete can be broken up using machinery. This is one stage in recycling the components of reinforced concrete.

Systems

A system comprises parts or components that work together to control a task or activity. a system consists of imputs, processes and outputs. all designs and manufacturing tasks are made up of systems, from printing a simple image onto a piece of paper to manufacturing a sports car.#

Whithin each systems there can be many subtasks or subsystems. For example, a digital camara has a power system and a memory storage system, amoungst others. A camaras power system would comprise subsystems to operate the charging of the battery, indicatewhen it is fully charged or empty, and automatically turn off when not in use.

Inputs

Input devices allow systems to understand changes in the environment around them. ExamplesInput devices allow systems to understand changes in the environment around them. Examples include a sensor such as a light-dependent resistor (LDR) that senses light levels for street lamps to know when it is dark, or thermistors that detect when it is too hot or cold in a room. include a sensor such as a light-dependent resistor (LDR) that senses light levels for street lamps to know when it is dark, or thermistors that detect when it is too hot or cold in a room.

There pupose

 · examples of real-world signals include light level, temperature and pressure

·examples of electronic signals include voltage and current

Input devices are usually either switches or sensors.

Outputs

Output components are used to give off a stimulus as light, heat, movement or sound. Some output components sucvh as light emittingdiodes(LEDs) require very little power to drive them but others, such as heating elements, require a lot of energy. Output components sometimes need to be connectde to devices called transducer driverswhich increasethe power avaliable and help a circuit to perform correctly without overheating.

Most output components (excluding lamps) have polarity.

Electronic Systems 

Have both Inputs and Outputs with the output or outputs being produced by processing the inputs. Also, the input signal(s) may cause the process to change or may itself cause the operation of the system to change. Therefore the input(s) to a system is the “cause” of the change, while the resulting action that occurs on the systems output due to this cause being present is called the “effect”, with the effect being a consequence of the cause.In other words, an electronic system can be classed as “causal” in nature as there is a direct relationship between its input and its output. Electronic systems analysis and process control theory are generally based upon this Cause and Effect analysis.So for example in an audio system, a microphone (input device) causes sound waves to be converted into electrical signals for the amplifier to amplify (a process), and a loudspeaker (output device) produces sound waves as an effect of being driven by the amplifiers electrical signals.But an electronic system need not be a simple or single operation. It can also be an interconnection of several sub-systems all working together within the same overall system.Our audio system could for example, involve the connection of a CD player, or a DVD player, an MP3 player, or a radio receiver all being multiple inputs to the same amplifier which in turn drives one or more sets of stereo or home theatre type surround loudspeakers.But an electronic system can not just be a collection of inputs and outputs, it must “do something”, even if it is just to monitor a switch or to turn “ON” a light. We know that sensors are input devices that detect or turn real world measurements into electronic signals which can then be processed. These electrical signals can be in the form of either voltages or currents within a circuit. The opposite or output device is called an actuator, that converts the processed signal into some operation or action, usually in the form of mechanical movement.

Types of Motion

Mechanical devices all have an inputmotion, which transforms into force to make an output motion. The four types of motion are:

• linear
• rotary
• reciprocating
• oscillating

First order levers (Class 1) place the fulcrum between the effort and the load. An example would be a seesaw, which places the fulcrum in the centre and allows equally weighted children to lift each other up.

Second order levers (Class 2) place the fulcrum at one end of the lever and the effort at the other, with the load in the centre. The closer together the fulcrum and load are, the easier it is to lift the load. Examples include wheelbarrows, nutcrackers and some bottle openers.

Third order leavers (Class 3) place the effort between the fulcrum and the load. If the effort and the fulcrum are further apart, it becomes easier to lift. A third order lever does not have the mechanical advantage of first order levers or second order levers so are less common. They are generally used for moving small or delicate items. Examples include tweezers or fishing rods.