Watt from Ampere and Volt

Calculator and formulas for electrical power from current and voltage

Power Calculator

Calculate Electrical Power

This function calculates power in watts from current and voltage. Enter the current in amperes and the voltage in volts.

Result
Power P:

Electrical Power

The Power Triangle: P = U × I

Main Formula
P = U × I

Power = Voltage × Current

Parameters
\(\displaystyle P\) = Power [W] (Watt)
\(\displaystyle U\) = Voltage [V] (Volt)
\(\displaystyle I\) = Current [A] (Ampere)
Example Calculation
\[P = U \times I = 230V \times 10A = 2300W = 2{,}3kW\]

Typical household appliance power

Power Units

Overview of Power Units

Electrical Power
Milliwatt (mW):
10⁻³ W
Watt (W):
Base Unit
Kilowatt (kW):
10³ W
Megawatt (MW):
10⁶ W
Typical Applications
LED Lamp:
5-15 W
Smartphone Charger:
20-25 W
Microwave:
800-1200 W
Electric Car:
50-150 kW

Example Calculations

Practical Calculation Examples

Example 1: Household Appliance

Given: I = 10A, U = 230V (typical household current)

\[P = U \times I = 230V \times 10A = 2300W = 2{,}3kW\]
Typical power for a kettle or heater
Example 2: LED Lighting

Given: I = 0.043A, U = 230V (LED lamp)

\[P = U \times I = 230V \times 0{,}043A = 9{,}89W \approx 10W\]
Energy-efficient LED lighting
Example 3: Industrial Application

Given: I = 100A, U = 400V (three-phase, one phase)

\[P = U \times I = 400V \times 100A = 40{,}000W = 40kW\]
Industrial motor or large machine
Power Ranges of Various Devices
Small Devices:
Smartphone: 5-25 W
LED Lamp: 5-15 W
Radio: 10-50 W
Laptop: 30-100 W
Household Devices:
Refrigerator: 100-300 W
Television: 100-400 W
Washing Machine: 1500-2500 W
Microwave: 800-1200 W
Industrial Applications:
Electric Car: 50-150 kW
Industrial Motor: 10-500 kW
Welding Machine: 5-15 kW
Crane System: 100-1000 kW

Formula for Power Calculation

Basics of Electrical Power

Electrical power is the product of voltage and current. It indicates how much electrical energy is converted per unit of time.

Main Formula
P = U × I
Power = Voltage × Current

Extended Formulas

With Resistance
\[P = I^2 \times R\]
\[P = \frac{U^2}{R}\]
Alternating Current
\[P = U \times I \times \cos(\phi)\]

With power factor cos(φ)

Practical Applications

Home Installation
  • Fuse calculation
  • Cable cross-section
  • Energy cost calculation
  • Load distribution
Industry
  • Motor design
  • Energy management
  • Load curve analysis
  • Efficiency optimization
Electromobility
  • Charging infrastructure
  • Battery management
  • Range calculation
  • Fast charging technology

Important Notes

Calculation Aspects
  • Direct Current: P = U × I (direct calculation)
  • Alternating Current (resistive load): P = U × I
  • Alternating Current (reactive load): P = U × I × cos(φ)
  • Three-phase: P = √3 × U × I × cos(φ)
  • Power loss: P = I² × R (heat losses)
  • Efficiency: η = P_out / P_in

Design Notes

Practical Considerations
  • Fuses: Rated current based on continuous power
  • Cooling: Power loss determines cooling requirements
  • Energy efficiency: Efficiency optimization reduces losses
  • Peak loads: Consider short-term overloads
  • Power factor: cos(φ) affects apparent power
  • Harmonics: Harmonics increase apparent power

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