A diode that conducts when a value voltage is applied. Used to protect circuits from overload.

The sum divided by the number of items.

There are several awarding bodies City and Guilds: AQA, Edexcel and OCR for example.

Transmission system that uses all four wheels of a vehicle to provide a drive. This term is usually used on vehicles with a permanent four wheel drive that transfers drive to another axle when some loss of drive occurs on the main drive axle. The term 4WD or 4x4 is used for used for vehicles with selectable four wheel drive.

Transmission system that uses all four wheels of a vehicle to provide a drive. This term is usually used on vehicles with a permanent four wheel drive that transfers drive to another axle when some loss of drive occurs on the main drive axle. The term 4WD or 4x4 is used for vehicles with selectable four wheel drive.

Along the axis of a shaft.

Movement along or parallel to the axis of a shaft.

The centre line through a shaft or axle. The centre about which an object rotates or where the object is in equilibrium.

Horizontal transverse shaft or beam with spindles on which road wheels are mounted.

Term used to describe the forces acting on an axle.