The total resistance in a series circuit is equal to the sum of the individual resistances. A parallel circuit provides alternate paths for current to follow. The total current in a parallel circuit is equal to the sum of the current passing through different branches in the circuit. The drop in potential difference across all branches in a parallel circuit is the same. An equivalent resistance can be considered to consist of a single resistance which replaces two or more resistances.
Most electric circuits use a combination of series and parallel arrangements.
Ohm's Law and Kirchhoff's Laws are useful in analyzing these types of circuits. Draw a schematic diagram of a series circuit and a parallel circuit. Recognize and apply mathematical expressions for current, potential difference, and resistance in series and parallel circuits. Determine an equivalent resistance to replace two or more resistors in an electric circuit. Apply an understanding of equivalent resistance in problem solving.