Glossary

GLOSSARY

For the purposes of this study design the following definitions will apply.

Alternating Current (AC):  

Alternating Current (AC) is a form of electricity where electrons rapidly

change direction. AC current varies over time, creating a sine-wave

waveform.

AC and DC waveforms

Acceleration (A): 

The rate of change in velocity.

Amperes (A) 

The unit of current measurement (often referred to as amps). The amount

of electric charge flowing through a circuit.

Belt and pulley 

A continuous loop (usually of rubber) used to connect two pulleys over a

distance in order to transfer rotary motion.

Cam and follower 

An elliptical piece (cam) that rotates on a shaft that lifts and drops a rod

(follower).

Capacitor 

A device that stores an electric charge.

Closed loop (control) system 

A system that uses self-monitoring or feedback and self-adjustment to

alter or maintain a predetermined level of output. The use of a thermostat

can provide a basic closed loop system, with a set temperature output.

Compression control system 

A force that tends to shorten or squeeze something, decreasing its

volume. A system which manages or manipulates an output through direct,

predetermined or programmed instruction.

Crank

A handle with a lever used to provide mechanical advantage.

Diode 

A device that allows current to flow in one direction only.

Direct Current (DC) 

Direct Current (DC) is a form of electricity where all electrons move in

the same direction. DC current does not vary with time, creating a flat

waveform.

Efficiency A measure of how well energy is used, determined by Energy out/Energy

in.

Effort 

An applied force.

Electrical charge (Q–Coulomb) 

Amount of stored electrons (Charge = Capacitance × Voltage) (Q = C × V).

Element 

A distinct part of a process or actual part of a system that can be

identified, that is generally not considered a component.

Feedback 

A monitoring or sampling of the output which is directed back to the input

controls. A system with feedback is a closed loop system.

Force (F) 

A push or a pull (Force = Mass × Acceleration) (F = M × A).

Fossil fuels 

Decayed matter over millennia from which chemical fuels are derived,

including coal, oil and natural gas.

Frequency (f) 

The number of cycles, oscillations, or vibrations of a wave motion or

oscillation in unit time.

Friction 

A force resisting motion related to the rubbing between surfaces.

Fuel cell 

Cell that produces electricity by oxidation of fuel (hydrogen and oxygen or

zinc and air). Can be used in electric cars.

Gear 

A toothed component that meshes with another to transfer motion in

mechanical systems.

Simple gear train 

Two or more gears that mesh, used to increase or

decrease speed, and to change direction.

Compound gear 

A compound gear is made up of two or more gears

that are joined together and share the same shaft.

Compound gear train 

A compound gear train is a combination of gears

and axles or shafts that have at least one axle or

shaft with a compound gear.

Gear ratio 

The relationship of the number of turns between two gears expressed as

a ratio, that is, the number of turns of the driver to one turn of the driven

(x:1). For example, (for a reduction gear box) a driver gear has 40 teeth and

the driven gear has 80 teeth; using the formula driven ÷ driver the ratio is

expressed as 2:1 or for two turns of the driver gear the driven gear turns

once.

Inclined plane 

A wedge, ramp or slope.

Infared transmitter and receiver 

Data transmission and reception via non visible light, e.g. as used in a

television remote control.

Input 

The starting point, where the raw elements are applied, such as energy,

material, data or physical action.

Integrated circuit (IC) 

A single electronic component that contains within it circuitry to perform a

set of functions.

Integrated system 

A system that contains mechanical, pneumatic or hydraulic functions

together with electrical or electronic (electrotechnology) function/s.

Lever 

A simple machine that provides mechanical advantage.

Light dependent resistor (LDR) 

A device that increases in resistance with decreasing light.

Light emitting diode (LED) 

A specific diode designed to give off light when current flows through it.

Linear motion 

Straight line movement in one direction.

Load (N – Newton) (mechanical) 

A force or burden (Load = Mass × Acceleration) (N = M × A).

Load (Ω – Ohmns) r (R) (electrical) 

A resistive device at the output where the electrical power is dissipated.

Logic gates 

A configuration of transistors that performs a defined switching sequence

or logic function.

Mass (M) 

The amount of matter in an object.

Mechanical advantage (MA) 

The ratio of the force performing the work done by a mechanism to the

input force, e.g. as provided by a lever.

Micro-controller 

A micro-controller is an electronic device that contains a combination of

processor, memory and input/output facilities.

Moments about a point 

A turning or twisting force at a distance from a turning point.

Motion 

The act of changing position. The types of motion or movement of

mechanisms are linear, rotary, reciprocating and oscillating.

Ohm’s Law 

The rules of the relationship between voltage, current and resistance in DC

circuits (Voltage = Current × Resistance) (V = I × R).

Ohms (Ω) or (R) 

The unit of electrical resistance measurement.

Open loop system 

A system that has no monitoring or self adjustment, which results in an

output unaffected by the inputs; its function can be altered only by human

intervention.

Oscillating motion 

Circular motion in two directions – backwards and forwards.

Output 

The derived outcome produced by the process that occurs within a

system.

Piston 

A mechanism that provides the compression of gases within a cylinder.

Pneumatic 

The use of air pressure to transfer force or motion.

Polarity 

The condition of a body or system in which it has opposing physical

properties at different points, especially magnetic poles or electric charge.

Power (P – Watts) 

The rate at which work is done or energy used.

Electrical term: (Power = Voltage × Current), (P = V × I)

1 horsepower (hp) = 746 Watts of power.

Printed circuit boards (PCBs) 

A circuit board usually made of fibreglass on which copper tracks are

‘printed’ to make an orderly connection of components.

Process 

How the inputs of a system work together in a system to achieve a desired

output.

Programmable Interface Controller, also

known as Programmable Integrated

Circuit (PIC)

An electronic component which can be externally programmed to perform

a series of functions.

Prototype 

An electronic component which can be externally programmed to perform

a series of functions.

Pulley 

A mechanical component that together with a belt transfers rotary motion.

Reciprocating motion 

Motion alternately backward and forward, or up and down, as of a piston

rod.

Rectifier 

A device that converts alternating current (AC) to direct current (DC)

(unregulated).

Relay 

An electromagnetic switch.

Renewable energy sources 

Sources of energy that will never run out or that can be replenished within

a span of time, through natural ecological cycles or sound management

practices, e.g. wind, solar, wave, bio-fuels, firewood. Non-renewable

energy sources are fossil fuels (coal, oil and gas).

Resistance (Ω or R – Ohms) 

The degree to which electron flow is impeded.

Resistor 

A device that provides a specified amount of opposition to the flow of

current. Resistance is measured in Ohms.

Rotary motion 

Circular movement in one direction.

Schematic 

A structural or procedural diagram, especially of an electrical or a

mechanical system.

Screw 

A mechanical device consisting of a cylinder or cone that has one or more

helical (advancing spiral) ridges winding around it. Not only used as a fixing

device, the screw principle is applied in machinery such as a worm gear or

a grain lifter.

Shaft 

A rod, bar or tube that connects two rotating components.

Speed 

The rate of change of position over time.

Spring 

A device, such as a coil or strip of steel, that stores potential energy when

it is compressed, stretched, or bent and releases it when the restraining

force is removed.

Sprocket 

A toothed mechanical component that when combined with a chain,

transfers rotary motion over a distance.

Switch 

A device which closes (turns on) or opens (turns off) a circuit, to interrupt

current flow.

Tension 

A force tending to stretch or elongate something.

Thermistor 

A device that changes resistance with a change in temperature, available

as both a positive or negative coefficient type.

Thermostat 

A device that closes (turns on) or opens (turns off) a circuit according to

temperature.

Torque 

A twisting force.

Trade-off 

A technological system or process which has benefit, but also has the

potential for detriment to society or the environment.

Transducers 

A device that transforms one form of energy to another form.

Transformer 

A device which can step up (increase) or step down (decrease) AC voltage.

Transistor 

A semiconductor device which can control current flow, used as an

amplifier or switch.

Velocity 

The rate of change of displacement over time.

Voltage (V) 

The electromagnetic force (EMF) at which electrons are moved.

Voltage regulator 

A device which provides a stable DC voltage power source within the

specified current range of the device.

Volts (V) 

The unit of voltage measurement.