Every electric circuit, no matter where it is or how large or little it is, has four fundamental components: an energy source (alternating current or direct current), a conductor (wire), an electrical load (device), and at least one controller (switch). Consider what occurs when you turn on a light in a room. You have just created a circuit between the electricity from the wall socket and the light bulb. The wire that connects your house to the street network is called an extension cord. It can be any length up to about 100 feet. A shorter length of cable may be used under the flooring or inside walls for smaller jobs.
The conductor is the copper wire within the cable that carries the current from place to place. The term "conductor" also includes the metal wires within appliances and devices that carry current to their own internal circuits or batteries. These include lamps, heaters, and fans. They are not part of the cable itself; instead they are insulated from the cable by layers of plastic or rubber sheathing.
The third component is the electrical load. This is the thing that uses energy from the power supply source. In our example with the light bulb, the load is the lamp. It converts electrical energy into light energy by passing a current through a filament, which glows blue-white when hot enough. The fourth component is the controller. This is the device that turns on and off the power to the load automatically.
The combination of these elements forms a circuit.
The three essential parts of any circuit are the power supply, the conductor, and the load. The power supply can be a single element such as a wall socket or battery, or it can be a group of elements working together such as an AC power line system or DC power grid. The conductor is a path that electricity can follow from one point to another. This could be a copper wire inside a house connection box, or it could be an optical fiber cable running across the country to a data center. The load is anything that uses electricity; it could be a light bulb, radio, or microwave oven. It can also be a group of devices used simultaneously such as several lights in a house, or it can be a single device such as a motor. The only requirement for something to be considered part of a circuit is that it should have two or more connections to the power supply and one or more connections to the load.
In addition to these essential components, some circuits need control signals to operate them.
Every electric circuit contains at least two components: a voltage source and a conductor. They may also include additional components like as light bulbs and switches, as seen in the basic circuit depicted in the picture below. This basic circuit's voltage source is a battery. It provides electricity to make the lights work. The conductor is made of copper wires that connect the lamps together. There must be a path for current to travel through the circuit. A simple way to think about this is that there must be a way for electricity to get from the positive side of the battery to the negative side or else the lights will not glow.
The first thing that is necessary for any circuit is something that can generate voltage. This could be an electrical outlet, a car battery, or even your hand if you are careful where you put it. Voltage sources provide energy to other parts of the circuit.
The second thing that is necessary for any circuit is something that can conduct electricity. A metal wire is enough for small circuits but electric circuits need something more substantial than wires to connect the various components together. Conductors pass current along their length until they reach another conductor or component that generates voltage. At this point, the current is stopped by either connecting the two electrodes together or by using a third electrode such as a ground.