Ohm's Law & Power Calculator
Enter any 2 known variables (Voltage, Current, Resistance, or Power) and instantly solve the rest with step-by-step formulas.
Use at least a 45 W Cerámica / Disipador (Chasis Aluminio)
Formulated by German physicist Georg Simon Ohm, it establishes that electric potential difference (V) across a conductor is directly proportional to current intensity (I) flowing through it, with resistance (R) serving as the constant of proportionality (V = I × R).
Combining Ohm's Law (V = I × R) with Joule's Law of Power (P = V × I) yields 12 exact algebraic equations, allowing any parameter to be solved from any 2 known values (e.g. P = I² × R, P = V² / R, V = √(P × R), I = √(P / R)).
As electrons move through resistive material, atomic collisions convert electrical energy into heat. Dissipated thermal power escalates quadratically with current (I²), making amperage the single most critical stress factor in conductor and component heating.
Ohmic materials (copper wires, metal film resistors) exhibit constant resistance across voltage ranges. Non-ohmic devices (diodes, LEDs, transistors, NTC/PTC thermistors) feature non-linear I-V curves where dynamic resistance changes with voltage or temperature.
1. Why Does Doubling Voltage Quadruple Power (4× Power)?
Common surprise when increasing from 12V to 24V creates 4 times more heat rather than double.
Remember P = V² / R. Doubling voltage (2V) results in (2V)² / R = 4 × (V² / R).
Doubling voltage across a fixed resistance simultaneously doubles current (I = V / R). Since power is P = V × I, total power scales by 2 × 2 = 4.
2. Excessive Voltage Drop in Long Cable Runs
Load voltage at the end of a line is noticeably lower than power supply output.
Increase cable cross-section (thicker wire / lower AWG number) or boost source voltage.
Cables possess intrinsic resistance R = ρ × (L / A). Flowing current causes drop V_drop = I × R_cable and wastes power P = I² × R_cable. In low-voltage DC lines, high current causes severe percentage loss.
3. Short Circuit Risk and Instant Thermal Fusion (R → 0 Ω)
Connecting supply terminals with near-zero resistance causes dangerous current surges and sparks.
Always install fast-acting fuses or circuit breakers rated for your maximum nominal circuit load.
According to Ohm's Law, as R approaches 0, theoretical current I = V / R approaches infinity. Actual current is limited only by source internal impedance, releasing hundreds of amps in milliseconds.
4. Watts (Power) vs Watt-Hours / kWh (Energy)
Distinguishing instantaneous power demand from accumulated battery or grid energy consumption.
Power (W) is the instant rate of energy consumption (P = V × I). Energy (Wh or kWh) is power multiplied by operational time (E = P × t).
A 1,000 W appliance operating for 30 minutes consumes 500 Wh (0.5 kWh). In battery systems, Ampere-hours (Ah) convert to energy via Energy (Wh) = Capacity (Ah) × Nominal Voltage (V).
The Law Denounced as 'Unacceptable Heresy'
When Georg Simon Ohm published his treatise in 1827, German academia dismissed his findings. The Prussian Minister of Education declared his work delusional and Ohm was forced to resign his professorship, living in obscurity until the Royal Society awarded him the Copley Medal 20 years later.
Why Power Grids Operate at 400,000 Volts
High-voltage transmission (400 kV) slashes the current I required for the same power throughput (P = V × I). Dropping current by 1,000× decreases cable resistive heating loss (P = I² × R) by a factor of 1,000,000×, enabling efficient long-distance power distribution.
Tungsten Filaments & Cold Resistance
A classic 60W incandescent lamp has a cold resistance of merely 18 Ω. Once energized, the tungsten filament reaches 2,500 °C, multiplying resistance by 13× to 880 Ω. This explains why light bulbs almost exclusively burn out at the exact instant of flicking the switch on (inrush surge).
The Famous 'Ohm's Triangle'
For over a century, physics curricula worldwide have taught the triangle diagram with V on top and I, R below. Covering the variable you need to calculate with your finger immediately reveals the formula: V = I × R, I = V / R, or R = V / I.