A capacitor is a device that stores energy in
the electric field created between a pair of conductors on which
opposite electric charges have been placed.
The transistor is a solid state semiconductor device which can be
used for amplification, switching, voltage stabilization,
signal modulation and many other functions.
A diode functions as the electronic version of a one-way valve. By
restricting the direction of movement of charge carriers, diodes
allow an electric current to flow in one direction, but blocks it
in the opposite direction.
Electrical connectors refer to a device for joining electrical
circuits together. In computing it can also be known as a physical