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Series and Parallel DC Circuits; Equivalent Resistance

Draw a circuit with resistors in parallel and in series. Calculate the voltage drop of a current across a resistor using Ohm’s law. Contrast the way total resistance is calculated for resistors in series and in parallel. Explain why total resistance of a parallel circuit is less than the smallest resistance of any of the resistors in that circuit. Calculate total resistance of a circuit that contains a mixture of resistors connected in series and in parallel. Most circuits have more than one component, called a resistor that limits the flow of charge in the circuit.

Figures (4)

A series circuit with a voltage source (such as a battery, or in this case a cell) and three resistance units
A diagram of several resistors, side by side, both leads of each connected to the same wires.
A diagram of several inductors, side by side, both leads of each connected to the same wires.
A diagram of several capacitors, side by side, both leads of each connected to the same wires.

Key Points

  • In a series circuit, the current that flows through each of the components is the same, and the voltage across the circuit is the sum of the individual voltage drops across each component.
  • In a parallel circuit, the voltage across each of the components is the same, and the total current is the sum of the currents flowing through each component.
  • Ohm's law states that in a well-behaved conductor (a so-called ohmic conductor), the electric current between two points is directly proportional to the voltage (the difference of electric potential) across the two points.
  • Ohm's law is an empirical relation which accurately describes the conductivity of the vast majority of electrically conductive materials over many orders of magnitude of current.
  • A matrix version of Kirchhoff's current law is the basis of most circuit simulation software, such as SPICE.
  • If each bulb is wired to the battery in a separate loop, the bulbs are said to be in parallel.

Terms

Tap a term for a plain-language explanation.

Sources & licensing(4)