Ri

Ribbon Cable
Any cable constructed as a ribbon with parallel elements.
Riboflavin
Commonly known as vitamin B2.
Ribonucleic Acid
One of the three major macromolecules, along with DNA and proteins, that are essential for all known forms of life.
Ribosomal RNA
A basic building block for ribosomes.
Ribosome
Site of protein synthesis.
Rich Combustion
Having a relatively high proportion of fuel to oxidizer. Having a value greater than stoichiometric.
Richardson Number
A nondimensional number arising in the study of shearing flows of a stratified fluid.
Richter Scale
A measure of the magnitude of an earthquake at its epicentre. Each point increase on the Richter scale is a 30 times increase in the magnitude.
Ride Height
Distance between the underside of a vehicle and the ground.
Ride Quality
A measure of the isolation from road inputs the suspension transfers to the vehicle without compromising vehicle control.
Riffler
A small file with a curved surface.
Right Angle
right angle = π/2 radians = 90°
Right Atrium
The right upper chamber of the heart.
Right Hand Thread
A screw thread that is screwed in by rotating clockwise. Most threads are right handed.
Right Hand Tractor Propeller
The propeller rotated clockwise when viewed from the rear.
Right Triangle
A triangle that contains a right angle.
Right Ventricle
The right lower chamber of the heart.
Rigid
An idealized concept meaning something which does not deform under loading.
Rigid Body Modes
These modes exist for all objects and are the modes of vibration where the object itself remains rigid and are the rotation or translational modes of the object on its mounting system.
Rigid Coaxial Line
A coaxial line consisting of a central insulated wire mounted inside of a tubular outer conductor.
Rigid Connection
In two dimensions, a fixed connection between two members restrains all three degrees of freedom of the connected member with respect to one another.
Rigid Joint
Prevents adjacent parts from moving or rotating past one another.
Ring
An additive commutative group in which a second operation (normally considered as multiplication) is also defined.
Ring Grooves
Grooves cut in the piston barrel to hold the piston rings.
Ring Spanner
Each end of the spanner fits around the bolt head or nut.
Ringer Equivalence Number
Denotes the electrical load that a telephone has on the line, the maximum REN for the UK is 4.
Ringing
Continued oscillation after an external force or excitation is removed, as after a guitar string is plucked.
Ringing Oscillator
A sine-wave oscillator that is turned on and off at specific times.
Ripping Hammer
A hammer which looks like a claw hammer, but the claw is straight.
Ripple Frequency
The frequency of the ripple current.
Ripple Voltage
The alternating component of unidirectional voltage.
RISC
Reduced Instruction Set Computer, a computer architecture that has reduced chip complexity by using simpler processing instructions.
Rise Run
For smaller angles, the ratio obtained when the change in offset between two centre lines is divided by the distance along either centerline.
Rise Time
The time required for the output of a transducer to rise from 10% to 90% of its final value, as it responds to a step change in the measurand.
Risers
Rectangular copper or aluminum bars that connect circuit breakers, fusible switches, and transfer switches with the main system bus.
Riveting Hammer
A hammer with a special head for securing rivets.
Rivets
A permanent fixing used to join plates. The unheaded end is forged or flattened.