Resistors in series

Two elements are in series if they exclusively share the same node and therefore have the same current flowing through them.

\[R_{eq} = + R_2 + R_3 + ... + R_n\]

So long as the Resistors are in series

This can be considered a compression and like in any compression nothing is free and we lose some information. In this case, the information we lose is the individual voltages.

Resistors in parallel

Two or more elements are in parallel if they are connected to the same nodes and therefore have the same voltage across them.

\[R_{eq} = 1/R_1 + 1/R_2 + 1/R_3 + ... + 1/R_n\]

So long as the Resistors are in series

This can be considered a compression and like in any compression nothing is free and we lose some information. In this case, the information we lose is the individual currents.

Practical application of these rules

You can create almost any value resistance by combining any number of resistor. Cos as the prof said the shops don’t have all the possible resistances.

Voltage division rule

With resistors in series the current is a ratio of the resistances over the total resistance for the individual resistance

Current division rule

With resistors in series the current is a ratio of the resistances over the total resistance for the individual resistance