Calculate electrical power (wattage) using Ohm's Law or by multiplying voltage and current.
Voltage (V) & Current (A)
Voltage (V) & Resistance (Ω)
Current (A) & Resistance (Ω)
Calculated Wattage:
— Watts (W)
Understanding Wattage and Electrical Calculations
Wattage, measured in Watts (W), is the unit of electrical power. It represents the rate at which electrical energy is transferred or consumed. Understanding how to calculate wattage is fundamental in electronics, electrical engineering, and even for everyday tasks like choosing appliances or understanding energy bills.
Ohm's Law and Power Formulas
The relationship between voltage (V), current (I), resistance (R), and power (P) is primarily governed by Ohm's Law and its derived power formulas.
Key Formulas:
Power from Voltage and Current:
P = V × I
This is the most direct way to calculate power if you know the voltage across a component and the current flowing through it.
Power from Voltage and Resistance:
P = V² / R
This formula is useful when you know the voltage and the resistance of a circuit or component. It's derived by substituting Ohm's Law (I = V/R) into the P = V × I formula.
Power from Current and Resistance:
P = I² × R
This formula is applied when you know the current flowing through a component and its resistance. It's derived by substituting Ohm's Law (V = I × R) into the P = V × I formula.
Definitions:
Voltage (V): The electrical potential difference, measured in Volts (V). It's the "push" that drives electric charge.
Current (I): The flow rate of electric charge, measured in Amperes (A or Amps).
Resistance (R): The opposition to the flow of electric current, measured in Ohms (Ω).
Power (P): The rate of energy transfer, measured in Watts (W). 1 Watt is equal to 1 Joule per second.
When to Use the Wattage Calculator
This calculator is useful in various scenarios:
Electronics Projects: Determining the power consumption of components like LEDs, resistors, or small circuits.
Appliance Selection: Understanding the power requirements of household appliances.
Electrical Safety: Estimating power loads to ensure circuits are not overloaded.
Educational Purposes: Learning and verifying electrical calculations based on Ohm's Law.
Example Calculations:
Scenario 1: Using Voltage and Current
If a device operates at 120 Volts and draws 3 Amps of current, its wattage is:
P = 120 V × 3 A = 360 Watts
Scenario 2: Using Voltage and Resistance
Consider a heating element with a resistance of 50 Ohms connected to a 240 Volt source:
P = (240 V)² / 50 Ω = 57600 / 50 = 1152 Watts
Scenario 3: Using Current and Resistance
If a circuit has a total resistance of 10 Ohms and a current of 5 Amps flows through it:
P = (5 A)² × 10 Ω = 25 × 10 = 250 Watts
By accurately calculating wattage, you gain a better understanding of electrical energy usage and requirements.
function calculateWattage() {
var calculationType = document.getElementById("calculationType").value;
var wattage = 0;
var voltage, current, resistance;
if (calculationType === "voltageCurrent") {
voltage = parseFloat(document.getElementById("voltage").value);
current = parseFloat(document.getElementById("current").value);
if (!isNaN(voltage) && !isNaN(current) && voltage >= 0 && current >= 0) {
wattage = voltage * current;
} else {
alert("Please enter valid non-negative numbers for Voltage and Current.");
return;
}
} else if (calculationType === "voltageResistance") {
voltage = parseFloat(document.getElementById("voltageR").value);
resistance = parseFloat(document.getElementById("resistance").value);
if (!isNaN(voltage) && !isNaN(resistance) && voltage >= 0 && resistance > 0) {
wattage = (voltage * voltage) / resistance;
} else {
alert("Please enter valid non-negative numbers for Voltage and a positive number for Resistance.");
return;
}
} else if (calculationType === "currentResistance") {
current = parseFloat(document.getElementById("currentR").value);
resistance = parseFloat(document.getElementById("resistanceR").value);
if (!isNaN(current) && !isNaN(resistance) && current >= 0 && resistance > 0) {
wattage = (current * current) * resistance;
} else {
alert("Please enter valid non-negative numbers for Current and a positive number for Resistance.");
return;
}
}
document.getElementById("result-value").innerText = wattage.toFixed(2);
}
document.getElementById("calculationType").onchange = function() {
var type = this.value;
document.getElementById("voltageCurrentInputs").style.display = (type === "voltageCurrent") ? "block" : "none";
document.getElementById("voltageResistanceInputs").style.display = (type === "voltageResistance") ? "block" : "none";
document.getElementById("currentResistanceInputs").style.display = (type === "currentResistance") ? "block" : "none";
// Clear previous result when changing calculation type
document.getElementById("result-value").innerText = "–";
};