Understanding Appliance Circuit Conditions

When current can flow from point A to point B without interruption, it is called a complete circuit.

If there is a break in the path, current will not be able to flow from point A to point B, and the circuit is incomplete. Sometimes this break in the circuit is caused by design, such as when a switch is moved to its OFF position, or it can be caused by accident, such as a break in the wire, as shown in the following illustration.

Whenever there is a break in the path through which current should flow, it is referred to as an open circuit (see the illustration).

A closed circuit is one in which there is a complete path for the current to flow (see the illustration).

When resistance, or a load, is introduced in a circuit, it restricts the flow of current. The higher the resistance, the less current will flow. In the illustrations below, the variable resistor is used to show this effect.

Illustration A shows the variable resistor at its maximum setting, so that all of its resistance is introduced to the circuit. Thus, a minimum of current will flow, and the light is very dim.

Illustration B shows the variable resistor at its medium setting, so that only half of its resistance is introduced to the circuit. Thus, the current flow increases, and the light becomes brighter.

Illustration C shows the variable resistor at its minimum setting, so that none of its resistance is in the circuit. Thus, a maximum of current will flow, and the light is at its brightest level.