Ohm's Law Calculator

ANA›Life Services Authority›National Calculator Authority›Ohm's Law Calculator

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Ohm's Law Calculator

Enter any two known values to calculate the remaining unknowns using Ohm's Law (V = I × R).

Voltage (V) — volts

Current (I) — amperes

Resistance (R) — ohms

Power (P) — watts

Calculate

function ohmCalc() { var resultDiv = document.getElementById("ohm-result");

var vRaw = document.getElementById("ohm-voltage").value.trim(); var iRaw = document.getElementById("ohm-current").value.trim(); var rRaw = document.getElementById("ohm-resistance").value.trim(); var pRaw = document.getElementById("ohm-power").value.trim();

var V = vRaw !== "" ? parseFloat(vRaw) : null; var I = iRaw !== "" ? parseFloat(iRaw) : null; var R = rRaw !== "" ? parseFloat(rRaw) : null; var P = pRaw !== "" ? parseFloat(pRaw) : null;

// Validate provided values var inputs = {V: V, I: I, R: R, P: P}; for (var key in inputs) { if (inputs[key] !== null) { if (isNaN(inputs[key])) { resultDiv.innerHTML = "Error: All entered values must be valid numbers."; return; } if (inputs[key] Error: Values cannot be negative."; return; } } }

// Count provided values var provided = [V, I, R, P].filter(function(x){ return x !== null; }).length; if (provided Error: Please enter at least two known values."; return; }

// Solve using Ohm's Law: V = IR, P = VI = I²*R = V²/R // Try all combinations to derive unknowns

// Derive from V and I if (V !== null && I !== null) { if (I === 0) { resultDiv.innerHTML = "Error: Current cannot be zero (division by zero)."; return; } R = R !== null ? R : V / I; P = P !== null ? P : V * I; } // Derive from V and R else if (V !== null && R !== null) { if (R === 0) { resultDiv.innerHTML = "Error: Resistance cannot be zero (division by zero)."; return; } I = I !== null ? I : V / R; P = P !== null ? P : (V * V) / R; } // Derive from V and P else if (V !== null && P !== null) { if (V === 0) { resultDiv.innerHTML = "Error: Voltage cannot be zero for this calculation."; return; } I = I !== null ? I : P / V; R = R !== null ? R : (V * V) / P; } // Derive from I and R else if (I !== null && R !== null) { V = V !== null ? V : I * R; P = P !== null ? P : I * I * R; } // Derive from I and P else if (I !== null && P !== null) { if (I === 0) { resultDiv.innerHTML = "Error: Current cannot be zero (division by zero)."; return; } V = V !== null ? V : P / I; R = R !== null ? R : P / (I * I); } // Derive from R and P else if (R !== null && P !== null) { if (R === 0) { resultDiv.innerHTML = "Error: Resistance cannot be zero (division by zero)."; return; } I = I !== null ? I : Math.sqrt(P / R); V = V !== null ? V : Math.sqrt(P * R); }

// Final check for NaN/Infinity if (!isFinite(V) || !isFinite(I) || !isFinite(R) || !isFinite(P)) { resultDiv.innerHTML = "Error: Calculation resulted in an invalid value. Check your inputs."; return; }

function fmt(n) { return parseFloat(n.toPrecision(6)).toString(); }

resultDiv.innerHTML = "Results:" + "⚡ Voltage (V): " + fmt(V) + " V" + "🔌 Current (I): " + fmt(I) + " A" + "🔧 Resistance (R): " + fmt(R) + " Ω" + "💡 Power (P): " + fmt(P) + " W";

// Populate all fields with results document.getElementById("ohm-voltage").value = fmt(V); document.getElementById("ohm-current").value = fmt(I); document.getElementById("ohm-resistance").value = fmt(R); document.getElementById("ohm-power").value = fmt(P); }

#### Formulas

Ohm's Law: V = I × R Power: P = V × I = I² × R = V² / R Where: V = Voltage (volts, V) I = Current (amperes, A) R = Resistance (ohms, Ω) P = Power (watts, W)

#### Assumptions & References

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References

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