Electric Circuit:

Every  electrical  circuit  has  at  least  four  basic  categories:  (1) a  source  of  electromotive  force, (2) conductors, (3) load or loads, and (4) a few means of control.  Within Figure, the source of EMF is the battery; the conductors are wires that connect the several component categories; the resistor is the load; and a switch is used as the circuit control device.

Figure: Closed Circuit

A closed circuit is an uninterrupted, or unbroken, path for current from the source (EMF), by the load and back to the source.

An open circuit, or incomplete circuit, in the below Figure exists if a break in the circuit occurs; this avoids a full path for current flow.

Figure: Open Circuit

A short circuit is a circuit that offers extremely little resistance to current flow and could cause dangerously high current flow by a circuit that was display in the Figure. Short circuits are commonly caused through an inadvertent connection among two points in a circuit that offers little or no resistance to current flow. Shorting resistor R in the below Figure will probably cause the fuse to blow.

 Figure Short Circuit