Calculator
Example Data Table
| Case | Voltage | Current | Load Resistance | Internal Resistance | Power Factor | Delivered Power |
|---|---|---|---|---|---|---|
| Ideal DC source | 12 V | 2 A | 6 Ω | 0 Ω | 1 | 24 W |
| AC source | 120 V | 5 A | Not used | Not used | 0.8 | 480 W |
| Battery with loss | 24 V | Computed | 10 Ω | 0.5 Ω | 1 | 52.245 W |
Formula Used
Real power: P = V × I × PF
Resistance method: I = V ÷ R and P = V² ÷ R
Source with internal resistance: I = Vs ÷ (Rload + r)
Load power: Pload = I² × Rload × PF
Internal loss: Ploss = I² × r
Efficiency: η = Pload ÷ Psource × 100
The sign depends on current direction. If current leaves the positive terminal, the source delivers power. If current enters the positive terminal, the source absorbs power.
How to Use This Calculator
Select the calculation mode first. Use voltage and current when both values are known. Use voltage and resistance when the source is ideal and the load is resistive. Use source, load, and internal resistance when battery or supply loss matters.
Enter voltage in volts. Enter current in amperes when required. Enter resistance in ohms. Add power factor for AC circuits. Check the phase angle box when you prefer degrees. Press calculate. The result appears above the form.
Power Delivered by a Voltage Source
What This Tool Calculates
A voltage source can deliver power, absorb power, or lose power inside itself. This calculator checks those cases with practical inputs. It works for simple DC circuits. It also supports AC real power when a power factor or phase angle is known. The result shows delivered power in watts. It also reports current, terminal voltage, apparent power, reactive power, internal loss, and efficiency.
Why Direction Matters
Power sign is important in circuit analysis. A source delivers energy when current leaves its positive terminal. The computed power is positive in that case. A source absorbs energy when current enters its positive terminal. That can happen during battery charging or regenerative operation. The calculator includes a direction selector, so the sign follows the chosen convention.
Ideal and Practical Sources
An ideal voltage source keeps the same voltage at its terminals. Its power can be found from voltage and current. If only load resistance is known, Ohm’s law gives current first. Real supplies are different. They may have internal resistance. This resistance causes a voltage drop and heat loss. The load receives less power than the source generates.
AC Power Support
For AC circuits, voltage and current may not peak together. Power factor handles this phase difference. A power factor of one means all apparent power becomes real power. Lower values mean some energy moves back and forth each cycle. The calculator can use power factor directly. It can also compute power factor from a phase angle.
Practical Use
Use this calculator when checking batteries, DC adapters, solar systems, lab supplies, or AC loads. It helps compare delivered load power with internal loss. It also helps estimate efficiency. Always use RMS voltage and RMS current for AC calculations. For complex loads, confirm values with circuit measurements. This tool gives a useful engineering estimate. It does not replace safety testing or device specifications.
FAQs
What is power delivered by a voltage source?
It is the rate at which a source transfers electrical energy to a circuit or load. It is usually measured in watts.
What formula is used for delivered power?
The basic formula is P = V × I × PF. For DC resistive circuits, power factor is normally one.
Why can power be negative?
Negative power means the source is absorbing energy instead of delivering it. Battery charging is a common example.
What is internal resistance?
Internal resistance is resistance inside a source. It causes voltage drop and converts some energy into heat.
Does this calculator work for AC circuits?
Yes. Enter RMS voltage, RMS current, and power factor. You can also use a phase angle.
What is apparent power?
Apparent power equals voltage times current. It is measured in volt-amperes and includes real and reactive effects.
How is efficiency calculated?
Efficiency equals load power divided by total source power, then multiplied by 100. It is shown as a percentage.
Which mode should I choose?
Choose voltage and current for measured values. Choose resistance mode for an ideal source. Choose source-load mode when internal resistance matters.