Calculate voltage in a parallel circuit, where every branch shares the source voltage, plus branch currents, total current, resistance and power.

Ideal DC resistors across the same two points; wire and source resistance are ignored.

Current display unit

Parallel Voltage Formula

The following equality describes voltage across ideal resistive branches connected to the same two nodes. It does not add independent voltage sources in parallel.

V = v1 = v2 = v3 = v4 = v5

Formula source:  OpenStax University Physics Volume 2, 10.2: Resistors in Series and Parallel

  • Where V is the shared source/branch voltage
  • v1 to v5, etc., are voltage drops across branches connected in parallel

Every ideal parallel branch has the source voltage. For known branch resistances, Req = 1 / Σ(1/Ri), branch current Ii = V/Ri, total current = ΣIi, and total resistive power = V × total current. Reverse modes use V = total current × Req or Rbranch = V / branch current. Select two, three or four connected branches; only active branch resistances are used.

Definition

What is a parallel voltage?

A parallel voltage, or parallel circuit, is a circuit in which each component of the circuit receives the same amount of voltage as the source provides.

With an ideal 50 V source, each parallel resistor has 50 V across it. Branch currents can differ because resistance differs; voltage is not consumed or split between parallel branches. A voltage divider calculator instead models a different, series-resistor task. Real wire/source resistance, reactive loads, source limits and ratings are outside this calculator’s ideal DC model.

Example Problem

How to calculate parallel voltage?

For a parallel example, both resistors share the source voltage. Their currents add; their resistances combine reciprocally. The calculator also supports a source-voltage design from total current and a single-branch resistance design from its current.

For this example, the source voltage is 50 V, with 20 Ω and 30 Ω resistors connected in parallel.

The shared voltage, currents and equivalent resistance are:

V1 = V2 = Vsource = 50 V

I1 = 50/20 = 2.5 A; I2 = 50/30 ≈ 1.666667 A; total current ≈ 4.166667 A

Req = 1/(1/20 + 1/30) = 12 Ω; total power ≈ 208.333333 W. Choose Analyze parallel branches and enter 50 V, 20 Ω and 30 Ω to reproduce this result. Source mode with the same branches and 1 A gives 12 V. Branch mode at 12 V and 100 mA gives 120 Ω. A 0 V / 0 A pair does not determine a unique branch resistance; positive voltage with 0 A is an open circuit.