What is Ohm's Law and why is it fundamental to electronics?

Ohm's Law describes the relationship between voltage, current, and resistance: • Formula: V = I × R (Voltage = Current × Resistance) • Georg Ohm: German physicist who discovered this relationship • Foundation: Basis for all electrical circuit analysis • Units: Volts (V), Amperes (A), Ohms (Ω) This law allows you to find any electrical parameter if you know the other two.

How do I remember the different forms of Ohm's Law?

Use the VIR triangle memory method: • V = I × R (Voltage = Current × Resistance) • I = V / R (Current = Voltage / Resistance) • R = V / I (Resistance = Voltage / Current) • Power variations: P = V×I, P = I²×R, P = V²/R Cover the unknown variable in the triangle, and the formula is revealed!

What is electrical power and how does it relate to Ohm's Law?

Electrical Power is the rate of energy consumption: • Basic formula: P = V × I (Power = Voltage × Current) • Combined with Ohm's Law: P = I²R or P = V²/R • Units: Watts (W) • Applications: Power ratings, energy costs, heat generation • Example: 100W light bulb at 120V draws I = P/V = 0.83A Power calculations help size components and predict energy consumption.

When does Ohm's Law not apply?

Ohm's Law has limitations and doesn't apply to all materials: • Non-ohmic materials: LEDs, diodes, transistors • Temperature dependence: Resistance changes with heat • AC circuits: Must consider impedance, not just resistance • Superconductors: Zero resistance at certain temperatures • Arc discharge: Plasma and gas discharge devices For non-ohmic devices, use characteristic curves instead of Ohm's Law.

How do I apply Ohm's Law to series and parallel circuits?

Circuit configuration affects how Ohm's Law applies: • Series circuits: Same current, voltages add up • Parallel circuits: Same voltage, currents add up • Total resistance: Series: R_total = R1 + R2 + ... • Total resistance: Parallel: 1/R_total = 1/R1 + 1/R2 + ... • Analysis: Find equivalent resistance first, then apply Ohm's Law Complex circuits can be simplified using equivalent resistance methods.

Ohm's Law Calculator for Electrical Circuits

Calculate voltage, current, resistance, and power using Ohm's Law and electrical power formulas.

What would you like to calculate?

Required Fields

Enter any 2 values: Current + Resistance, Power + Current, or Power + Resistance

Voltage (V)

Current (A)

Resistance (Ω)

Power (W)

Quick Examples

Understanding Ohm's Law

Fundamental Formulas

V = I × R

Voltage equals Current times Resistance

P = V × I

Power equals Voltage times Current

P = I² × R

Power equals Current squared times Resistance

P = V² / R

Power equals Voltage squared divided by Resistance

Applications

Circuit Design: Calculate component values for desired electrical characteristics
Power Analysis: Determine power consumption and heat generation
Safety Calculations: Ensure components can handle electrical loads
Troubleshooting: Diagnose electrical problems in circuits

💡 Pro Tips

• Always check units: V (Volts), A (Amperes), Ω (Ohms), W (Watts)
• Use milliamps (mA) for small currents: 1A = 1000mA
• Power ratings are crucial for component selection
• Higher resistance means lower current for same voltage
• Use this calculator for both DC and AC circuits (AC may need additional power factor consideration)

Key Formulas

Ohm's Law: V = I × R

Power (Basic): P = V × I

Power (Current): P = I² × R

Power (Voltage): P = V² / R

Usage Tips

• Enter any two known values to calculate the others
• Voltage is measured in Volts (V)
• Current is measured in Amperes (A)
• Resistance is measured in Ohms (Ω)
• Power is measured in Watts (W)
• Use decimal values for fractional units

How to Use Ohm's Law Calculator

Choose what to calculate

Select whether you want to find voltage, current, resistance, or power based on what values you know.

Enter known values

Input at least two known electrical parameters. The calculator needs minimum two values to solve for the others.

Apply Ohm's Law

The calculator uses V = I × R and P = V × I relationships to find unknown values.

Review all parameters

Get comprehensive results showing voltage, current, resistance, and power for your circuit.

Verify safety limits

Check that calculated values are within safe operating limits for your components and application.

Pro Tips

Always verify results with actual measurements when possible
Consider component tolerances - resistors typically have ±5% or ±1% tolerance
Power ratings must not be exceeded to prevent component damage
Temperature affects resistance in most materials
Use appropriate safety margins for critical applications

Understanding Your Ohm's Law Results

Low Voltage (< 12V)

Safe voltage levels for most applications. Common in electronics, automotive, and low-power systems.

Medium Voltage (12V - 120V)

Household and automotive voltage levels. Requires proper safety precautions and appropriate components.

High Voltage (> 120V)

Dangerous voltage levels requiring special safety measures, qualified personnel, and proper electrical codes compliance.

High Current (> 10A)

High current requires appropriate wire gauge, fuses/breakers, and thermal management to prevent overheating.

Ohm's Law Calculator - Frequently Asked Questions

Ohm's Law at a glance

Enter any two of voltage, current, resistance, or power to solve the rest. Great for quick circuit checks and sizing components.

Circuit relationships

Ohm's Law Calculator: V, I, R, P with Unit Hints

Solve any two to find the other quantities. Handy for electronics and power checks with quick unit awareness.

Four-way solver

Compute V, I, R, P from any known pair.

Units aware

Volts, amps, ohms, watts with quick tips.

Practical uses

Sizing resistors, checking loads, sanity checks.

Circuit topics

Ohm's Law CalculatorElectrical Circuit CalculatorVoltage Current CalculatorResistance CalculatorElectrical Power Calculator

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Important: This Ohm's law calculator is designed for educational and basic electrical analysis purposes using fundamental electrical relationships and idealized circuit conditions. While calculations are mathematically accurate for basic DC circuits and resistive AC circuits, real-world electrical systems involve complex factors including temperature effects, reactive components, non-linear loads, and safety considerations that are not accounted for in simplified Ohm's law calculations. For electrical system design, troubleshooting, safety analysis, or any electrical work involving safety risks, always follow applicable electrical codes, use proper safety procedures, and consult qualified electricians or electrical engineers who can account for the specific complexities and safety requirements of your electrical application.

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