General Voltage Divider Calculator

Calculate the node voltage (VR), circuit current (I), and power dissipation (P1, P2) for a resistor network between two voltage sources (V1, V2).

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General Voltage Divider Circuit Explanation

This calculator analyzes a general voltage divider circuit. This circuit consists of two resistors (R1 and R2) connected in series between two different voltage sources (V1 and V2). The calculator determines the voltage (VR) at the node (junction point) between these two resistors, the current (I) flowing through the resistors, and the power dissipated by each resistor (P1, P2).

General Voltage Divider Circuit Diagram Diagram showing voltage source V1 connected to resistor R1, which is connected to node VR. Node VR is connected to resistor R2, which is connected to voltage source V2. Current I flows from V1 to V2 through R1 and R2. V1 R1 VR R2 V2 I = (V1-V2)/(R1+R2)

Calculation Formulas:

VR = ((V1 - V2) * R2) / (R1 + R2) + V2
I = (V1 - V2) / (R1 + R2)
P1 (Power in R1) = I² * R1
P2 (Power in R2) = I² * R2

Where:

  • V1: Voltage of the first source (Volts)
  • V2: Voltage of the second source (Volts)
  • R1: Resistance connected between V1 and node VR (Ohms, Ω)
  • R2: Resistance connected between node VR and V2 (Ohms, Ω)
  • VR: Calculated node voltage at the junction of R1 and R2 (Volts)
  • I: Total current flowing through the series resistors (Amperes, A). Assumes V1 > V2 for the positive direction shown in the diagram.
  • P1: Power dissipated by resistor R1 (Watts, W)
  • P2: Power dissipated by resistor R2 (Watts, W)

Notes:

  • If V2 is set to 0 (connected to ground), this formula simplifies to the standard grounded voltage divider: VR = V1 * (R2 / (R1 + R2)).
  • The direction of current (I) depends on the relative values of V1 and V2. If V2 > V1, the calculated current will be negative, indicating flow from V2 towards V1 (opposite to the arrow in the diagram).
  • Power dissipation (P1, P2) is always positive, regardless of current direction, as it depends on the square of the current (I²).

Practical Considerations:

  • Resistor Tolerance: Real-world resistors have manufacturing tolerances (e.g., ±5%, ±1%). This variation will affect the actual node voltage (VR) compared to the calculated value.
  • Resistor Power Rating: Resistors are rated for a maximum power dissipation. Ensure the calculated power (P1 and P2) is well below the power rating of the chosen resistors (typically, use resistors rated for at least twice the expected dissipation for safety and longevity).
  • Load Effect: Connecting any load (another circuit component) to the VR node will draw current and change the effective resistance of the lower part of the divider, thus altering the actual VR voltage. This calculator assumes no load is connected to VR (i.e., the output impedance is infinite).
  • Temperature Coefficient: Resistor values can change slightly with temperature. For high-precision applications, consider the temperature coefficient of the resistors.