Unit 2 - Energy, Materials, Systems and Devices

How does fracking work?

A well is drilled into crust until it hits shale rock, sending a high-pressure mixture of water, sand and chemicals to release the gas.

How is a fossil fuel used to generate electricity?

As the fossil fuel burns it generates heat, which is used to create steam that drives a turbine to generate electricity.

What is potential energy?

Stored energy to be released

What is kinetic energy?

• The energy an object has due to its motion • Can be transferred

How are flywheels used in the National Grid?

• When there's low demand, surplus energy spins a flywheel • Flywheels maintain momentum due to an almost frictionless environment • If demand rises the momentum is used to drive a generator to feed energy back into the grid

How do pneumatic systems work?

Pneumatic systems rely on a constant supply of compressed air, provided by an air compressor, to produce a force

How do hydraulic systems work?

Hydraulic systems rely on compressed fluid, provided by a pump, to produce a force

How do batteries work?

They store chemical energy and chemical reactions are used to generate electricity

Give a suitable material for surgical sutures or drug delivery

Biodegradable polymers, break down after use

Give a suitable material to use for receptions desks or door fronts and why

flexible MDF, can be folded into curved desks etc.

Suggest what can be used for joint replacement or fibre optics and why

titanium, strong and light

Suggest what can be used for screens on handheld devices and why

LCDs, compact, light and have low power use

Suggest a suitable material for a frying pan base or antifraud banknotes and why

Teflon, creates a non-stick surface and water-proof

Suggest a suitable material for prototypes and why

polymorph, easy to remould

Why are biodegradable polymers carbon neutral?

Energy used in manufacturing and transport comes from vegetable starch that absorb CO2 during growth, which offsets the CO2 released

Suggest a suitable material for car helmets and why

• Glass-reinforced plastic • Light and strong • Corrosion, chemical and heat resistant

Suggest a suitable material for race cars and why

• Carbon fibre • Light and strong • Good tensile strength • Water and chemical proof

Suggest a suitable material for summer clothing and why

• Gore-Tex • Waterproof • Breathable as moisture vapour can escape

Suggest a suitable material for armour and why

• Kevlar • Very strong and hard-wearing • Cut and tear resistant • High thermal protection

Suggest a suitable material for fire blankets and why

• Fire-resistant fabrics • Resist heat and ignition from naked flame

Suggest a suitable material for medical textiles and why

• Microfibres • Absorbent and fast-drying

Describe the process of making glass-reinforced plastic

1. Prepare mold

2. Apply release agent

3. Apply gel coat

4. Apply GRP matting

5. Apply resin and work it evenly into the matting

6. Clamp in position and leave to cure

7. Release mold

8. Trim and finish workpiece

What does analogue mean?

continuous variation with no set scale

What does digital mean?

signals that are on or off with a set scale

Name a smart material affected by sound

piezoelectric material

Name a smart material affect by UV rays

Photochromic pigments

Name smart materials affected by pressure

QTC and piezoelectric material

Name smart materials affected by electricity

QTC, piezoelectric material and shape memory alloy

Name smart materials affected by heat

Thermochromic pigments and shape memory alloy

Name a smart material affected by pH

litmus paper

Name smart materials affected by stress

Piezoelectric material, self-healing polymers

Give an example of a shape memory alloy

Nitinol - alloy of nickel and titanium

Give an example of a piezoelectric material

quartz

How does self healing concrete work?

• When cracks appear water seeps into them rupturing spheres of food and bacteria and activating them • Bacteria begins to feed resulting in calcium carbonate that bonds the concrete and fills the crack

How does QTC work?

• QTC changes its electrical resistance based on changes in applied force. • The more force applied the lower the resistance

How do piezoelectric materials work?

They change shape if voltage is applied

What does a speaker do?

emit sound - output

What does a LDR do?

resistance decreases when light intensity increases - input

What does a LED do?

emits light when a current passes through it - output

What does a push-to-make switch do?

provides a momentary connection - input

What does a push-to-brake switch do?

provide a temporary disconnection - input

What does a buzzer do?

produces an audio signal - output

What does a thermistor do?

resistance decreases when temperature increases - input

What does a toggle switch do?

latches on a connection - input

What is an open loop system?

A system that does not respond to changing conditions

What is a closed loop system?

Uses feedback built into the device to respond to changing conditions

What is a monostable device?

A signal pulse is triggered by a switch or sensor - used for timing length of an event

What is an astable device?

Produces a stream of pulses that are oscillating and constant

What is a linkage?

changes magnitude/direction of a force

What is a class 1 lever?

axis of rotation (fulcrum) is between the effort (force) and load

What is a class 2 lever?

load is between the axis of rotation (fulcrum) and the effort (force)

What does oscillating mean?

repeated back and forth movement of an object

What does reciprocating mean?

repetitive linear motion

What is an idler gear?

A gear that allows the driver gear and the driven gear to turn in the same direction

What is an eccentric cam?

round with hole for offcentred camshaft

What is a snail cam?

long dwell, slow rise, sudden drop

What is a pear cam?

long dwell, rapid rise and fall

What is a constant velocity cam?

designed to have no dwell period

How are pulleys adapted?

• Pulley wheels have V-shaped grooves for extra friction from larger surface area, as well as to insure the belt is engaged • Belts may have notches for more efficient flexing • Pulleys attach to driver shafts to transfer motion to other parts of the mechanism