Introduction

Switch, based on a definition by Merriam-Webster, is a device for making, breaking, or changing the connections in an electrical circuit.

Electronics switch, on the other hand, could connect or disconnect connections by electronics signals. Examples are bipolar-junction transistors (BJTs), metal–oxide–semiconductor field-effect transistors (MOSFETs), and electromechanical relays.

BJT

To control a BJT, a small amount of current is fed to the base to enable high-current conduction from the collector to emitter. The current from base and collector terminals combines at the emitter terminal.

MOSFET

To control a MOSFET, a voltage of around 3-10V is fed between the gate and source. The MOSFET then enables conduction from drain to source.

Relay

A relay usually consists of a coil that act as a magnet to connect two terminals.