Ley de Ohm (V = I · R)Física
What is Ohm's Law?
The fundamental electrical relationship stating that potential difference (Voltage) directly equals current multiplied by circuit resistance.
ELECTRONICS ENGINEERING & CIRCUITS
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.
Instant bi-directional math — Exact floating point precision
Presets:
V
InputI
InputR
P
Technical Summary
Voltage:12.000 V
Current:2.500 A
Resistance:4.800 Ω
Power dissipated:30.000 W
Suggested Resistor Rating:
Use at least a 45 W Cerámica / Disipador (Chasis Aluminio)
Step-by-Step Mathematical Solution
R = V / IR
12 V / 2.5 A = 4.8000 Ω
P = V × IP
12 V × 2.5 A = 30.0000 W
Ohm's Law Fundamentals (1827)
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).
SI Units: Volts (V), Amperes (A), and Ohms (Ω). 1 Ω = 1 V / 1 A.
12 Formulas of Ohm's & Joule's Wheel
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)).
Simplicity: Any linear circuit is 100% solved with just 2 known variables.
Joule Effect & Thermal Loss (P = I²R)
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.
Safety: Doubling current quadruples the heat generated in the resistor or cable.
Ohmic vs Non-Ohmic Devices
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.
Distinction: Pure Ohm's Law applies strictly to linear passive components.
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.
Quick Fix
Remember P = V² / R. Doubling voltage (2V) results in (2V)² / R = 4 × (V² / R).
Technical Insight
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.
Quick Fix
Increase cable cross-section (thicker wire / lower AWG number) or boost source voltage.
Technical Insight
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.
Quick Fix
Always install fast-acting fuses or circuit breakers rated for your maximum nominal circuit load.
Technical Insight
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.
Quick Fix
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).
Technical Insight
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).
Misunderstood Genius#1
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.
Grid Transmission Physics#2
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.
Curious Materials#3
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).
Classic Mnemonic#4
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.
Electrodynamics & Ohm's Law Glossary
Learn the fundamental concepts, protocols, and technical terminology of this tool.
Voltaje (V)Electricidad
What is Voltage?
The electromotive potential difference measured in Volts propelling charge carriers through a closed circuit loop.
Corriente Eléctrica (Amperios)Electricidad
What is electric current?
The continuous rate of electric charge flow passing through a conductor cross-section per second, measured in Amperes (A).
Potencia Eléctrica (Watts / Ley de Joule)Potencia
What is electrical power in Watts?
The rate at which electrical energy is converted into work or thermal dissipation per unit time (P = V · I or P = I² · R), measured in Watts.