Electrical Glossary

The electrical world has more than its fair share of obscure terminology but, fortunately, not all of it has much relevance for boaters. The glossary on this page is by no means comprehensive in the overall scheme of things but contains the most common terms we're likely to meet afloat.

Absorption charge:  The second charging stage of a multi-stage charge regime.

Alternating current (AC):  A form of electricity that reverses direction - typically 50-60 cycles per second.

Alternator:  An electrical generator that produces an alternating current.

Amp Hour (Ah): One amp hour is equal to a current of one amp flowing for one hour.

Ampere (amp):  An ampere is the unit of electrical current flow.

Anode: The electrode through which a current enters and electrolyte. See Sacrificial Anode.

Battery: A device that stores electricity by means of chemical processes.

Battery combiner: A device that connects two or more batteries together once a certain charge level has been reached.

Bulk charge: The first charging stage of a multi-stage charge regime.

Circuit breaker:  A safety device that detects exessive power demands and switches off automatically.

Current:  The movement of electrons through a conductor.

Dezincification: A galvanic process affecting brass alloys where the zinc is eroded.

Diode:  A sort of one-way valve for electricity, through which current can only flow in one direction.

Direct current (DC):  The type of electricity we get from batteries. Current flows in one direction.

Electrolysis: A process by which chemically bonded compounds are separated by an electric current.

Electrolytic corrosion:  Corrosion due to electrolysis.

Electrolyte:  A substance that conducts electricity by ionisation. The liquid contained in batteries.

Float charge:  The third charging stage in in a multi-stage charghing regime.

Fuse:   A conductor designed to melt if overheated by exessive current.

Galvanic corrosion:  Electrical interaction between different metals immersed in an electrolyte. Distinct from electrolysis because there is no external current source.

Generator:  A device for producing an electric current.

Inductive loads:  Loads that produce a magnetic field, often accompanied by heat.

Inverter:  An electrical device for converting DC to AC power.

Ion:  An atom either missing an electron or having an extra one.

Kilovolt-Amp (kVA):  Unit commonly used to rate generators.

Kilowatt:  One thousand watts of electricity.

Light emitting diode:  Type of lighting having very low consumption.

Load:  Any device that comsumes electricity.

Modified sine wave:  An AC waveform that approximates a sine wave in a series of steps.

Multimeter:  An instrument for measuring various electrical values - volts, amps and ohms being typical.

Ohm:  The unit of electrical resistance.

Oscillator:  An electro-mechanical device for converting DC to AC.

Oscilloscope:  An instrument providing a visual display of an electrical waveform.

Parallel circuit:  A group of loads wired together so voltage remains constant and current varies.

Photon:  Think of it as a particle of light.

Photovoltaic:  A device that converts light into electricity.

Primary cell:  A battery where the chemical charges are irreversible - i.e. it can't be recharged.

Rectifier:  A device for converting AC into DC.

Residual Current Device (RCD):  A safety device that detects any imbalance between live and neutral wires and trips if one occurs.

Parallel circuit:  A group of loads wired together so voltage remains constant and current varies.

Photon:   Think of it as a particle of light.

Photovoltaic:   A device that converts light into electricity.

Primary cell:  A battery where the chemical charges are irreversible - i.e. it can't be recharged.

Rectifier:  A device for converting AC into DC.

Residual Current Device (RCD):  A safety device that detects any imbalance between live and neutral wires and trips if one occurs.

Resistance: Any opposition to the flow of current. See ohms.

Resistive loads:  Loads resulting purely from resistance.

Secondary cells:  Batteries where the chemical changes can be reversed - i.e. they can be recharged

Semi-conductor:  Conductors with a limited capacity to conduct electricity.

Series circuit:  A group of devices wired together so the amps remain constant but voltage varies.

Sine wave:  A smooth output waveform going above and below zero. What you would expect from top quality inverters.

Solenoid:  An electro-magnet in the form of a tunnel.

Specific gravity:  The density of a liquid compared to fresh water.

Splitting diode:  A device that divides a charghing current so it can charge more than one battery.

Volt:  A unit describing electrical force.

Watt:  A unit describing a measure of electrical force.