Ohm's Law Calculator
Calculate voltage, current, resistance, and power using fundamental electrical formulas
Calculate Electrical Values
Electrical potential difference
Electric current flow
Opposition to current flow
Electrical power consumption
Calculated Results
Formulas used:
V = I × R (Voltage = Current × Resistance)
I = V / R (Current = Voltage / Resistance)
R = V / I (Resistance = Voltage / Current)
P = V × I (Power = Voltage × Current)
P = I² × R (Power = Current² × Resistance)
P = V² / R (Power = Voltage² / Resistance)
Circuit Analysis
Example Calculations
Basic Circuit
Given: V = 12V, R = 6Ω
Find: Current and Power
Solution:
- I = V / R = 12V / 6Ω = 2A
- P = V × I = 12V × 2A = 24W
- P = V² / R = 12² / 6 = 144 / 6 = 24W ✓
LED Circuit with Current Limiting Resistor
Given: Supply = 9V, LED drop = 2V, Desired current = 20mA
Find: Required resistor value
Solution:
- Voltage across resistor = 9V - 2V = 7V
- R = V / I = 7V / 0.02A = 350Ω
- P = I² × R = (0.02)² × 350 = 0.14W
Power Dissipation in Resistor
Given: I = 5A, R = 10Ω
Find: Voltage and Power
Solution:
- V = I × R = 5A × 10Ω = 50V
- P = I² × R = 5² × 10 = 250W
- P = V × I = 50V × 5A = 250W ✓
Ohm's Law Formulas
Basic Relationships
V = I × R
I = V / R
R = V / I
Power Formulas
P = V × I
P = I² × R
P = V² / R
Safety Guidelines
Always turn off power before working on circuits
Use proper wire gauge for current ratings
Consider power dissipation for component ratings
High voltage requires special precautions
Check local electrical codes and regulations
Units Reference
Voltage (V)
Volts, kilovolts, millivolts, microvolts
Current (I)
Amperes, kiloamperes, milliamperes, microamperes
Resistance (R)
Ohms, kiloohms, megaohms, milliohms
Power (P)
Watts, kilowatts, milliwatts, horsepower
Understanding Ohm's Law
What is Ohm's Law?
Ohm's Law is a fundamental principle in electrical engineering and physics that describes the relationship between voltage, current, and resistance in an electrical circuit. Formulated by German physicist Georg Simon Ohm in 1827, it states that the current through a conductor is directly proportional to the voltage across it and inversely proportional to its resistance.
Key Relationships
- •Voltage (V): The electrical potential difference, measured in volts
- •Current (I): The flow of electric charge, measured in amperes
- •Resistance (R): Opposition to current flow, measured in ohms
- •Power (P): Rate of energy transfer, measured in watts
Applications
- Circuit Design: Calculate component values for desired operation
- Power Analysis: Determine power consumption and heat dissipation
- Safety Analysis: Ensure circuits operate within safe parameters
- Troubleshooting: Diagnose circuit problems and component failures
- Load Calculations: Size wiring and protection devices
- Efficiency Analysis: Optimize circuit performance
Limitations
- •Applies to linear, resistive elements only
- •Not valid for reactive components (capacitors, inductors)
- •Temperature effects may change resistance values
- •Non-linear devices require more complex analysis
Formula Derivations and Extensions
Basic Ohm's Law
V = I × R
Where voltage equals current times resistance
Rearranged forms:
I = V / R (Current)
R = V / I (Resistance)
Power Relationships
P = V × I (Power law)
Combining with Ohm's law:
P = I² × R (Joule heating)
P = V² / R (Voltage-based power)
Energy:
E = P × t (Energy = Power × Time)