How this calculation works
The Ohm's Law & Electrical Power Calculator computes voltage (V), electrical current (I in Amperes), resistance (R in Ohms), and dissipated power (P in Watts) based on fundamental DC and single-phase AC circuit equations.
Mathematical formula and logic
V = I × R, I = V / R, P = V × I = I² × R = V² / R.
Worked example
For a 120V circuit with a 10Ω resistive load: Current I = 120 / 10 = 12.0 Amps. Dissipated Power P = 120 × 12 = 1,440 Watts (1.44 kW).
Calculation assumptions
- Assumes direct current (DC) or pure resistive alternating current (AC) with unity power factor (cos φ = 1).
- Temperature coefficients of resistance are neglected for standard room temperature operation.
Frequently asked questions
What is Ohm's Law?
Ohm's Law states that the current (I) flowing through a conductor between two points is directly proportional to the voltage (V) across the two points and inversely proportional to the resistance (R): V = I × R.
How do I calculate electrical power in Watts?
Power in Watts equals Voltage multiplied by Current (P = V × I). Alternatively, P = I² × R or P = V² / R.
What is an Ampere (Amp)?
An Ampere is the SI unit of electrical current, representing a flow rate of 1 Coulomb of electrical charge (approx 6.242 × 10¹⁸ electrons) per second.
What happens to current if resistance is doubled?
If voltage remains constant, doubling the circuit resistance cuts the current in half (inverse relationship).
Does Ohm's Law apply to LEDs and semiconductors?
No, semiconductors (diodes, LEDs, transistors) are non-linear non-ohmic devices where resistance changes dynamically with applied voltage.