Circuits

Now that we have covered the basics of the electrostatic interaction between charges, we can begin to assemble electric circuits with them. To study circuits one conventionally draws them up on a piece of paper. In this and the following chapters you will see many of these drawings (many more than you would like, actually). These drawings will use symbols to indicate certain components in the circuits. It is therefore helpful to provide some sort of dictionary to list all symbols and translate their meaning.

This is done on this page. Of course you will not understand most of the symbols and their function yet. But this page is meant to come back to for easy reference in case that you have forgotten the meaning of a circuit symbol. The symbols are (from top to bottom):

Resistor:
Indicates the value of the Ohm resistance. It is represented by a zigzag line.
Inductance:
Indicates the presence of a coil or some other device that can act as an electromagnet. It is represented by a curly line.
Switch:
Can open and close a circuit. It is usually drawn in the open position.
Capacitor:
A capacitor is used to store charge. It is represented by two parallel thick lines of equal length with a thin gap between them.
Wires:
All black lines that connect the other circuit elements are considered wires. For the purpose of a circuit these wires have no properties. If the resistance of a wire is important for the circuit, then it needs to be explicitly represented by a resistor circuit element. It is also important to note that all parts of the wire are at exactly the same potential, even if several wires are connected in complicated ways.
Ground:
In some cases, it is important to indicate which part of the circuit is defined to have 0 potential, i.e. connected to the Earth. This is where the ground symbol comes in. It is represented by a series of parallel horizontal lines that become shorter and thinner.
Battery:
A battery is a source of constant potential V in a circuit. It is represented by two parallel lines of different length, where the longer one is positive by convention.
Alternating voltage:
We will see that potentials that oscillate in time have the greatest technological applications and give us new physical effects not observed in circuits with constant potential sources. Alternating voltage supplies are indicated by a circle with a sine-curve inside.

Please note: The choice of color is completely arbitrary. But the shape of these symbols is more or less the same in all text books or technical documents and manuals.