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⚡ Voltage Calculator

Calculate voltage using three different formulas — Ohm's Law (V = I × R), the power-current relationship (V = P / I), and the power-resistance relationship (V = √(P × R)). Select a mode, enter two known values, and get voltage in Volts with millivolt and kilovolt equivalents.

Calculation Mode

Voltage Formulas Explained

V = I × R  (Ohm's Law)

Voltage equals current multiplied by resistance. V = Volts, I = Amperes (A), R = Ohms (Ω). This is the most fundamental relationship in electrical engineering.

V = P / I  (Power ÷ Current)

Derived from the power formula P = V × I. Useful when you know a device's wattage and operating current.

V = √(P × R)  (Power × Resistance)

Derived by combining Ohm's Law with the power formula. Useful when current is unknown but power dissipation and resistance are known.

Worked Examples

Mode 1: V = I × R
I = 2 A, R = 60 Ω
V = 2 × 60 = 120 V
Mode 2: V = P / I
P = 1150 W, I = 5 A
V = 1150 / 5 = 230 V
Mode 3: V = √(P × R)
P = 2400 W, R = 24 Ω
V = √(2400 × 24) = √57600 = 240 V
'What is the difference between AC and DC voltage?', 'answer' => 'DC (Direct Current) voltage is constant and flows in one direction — like a battery (1.5 V, 9 V, 12 V). AC (Alternating Current) voltage reverses direction periodically at a set frequency (50 Hz in India/UK/Europe, 60 Hz in US). Household mains is AC: 230 V in most of the world, 120 V in North America.'], ['question' => 'What is RMS voltage?', 'answer' => 'RMS (Root Mean Square) voltage is the effective value of an AC voltage — the DC equivalent that would produce the same heating effect. For a pure sine wave, V_RMS = V_peak / √2 ≈ 0.707 × V_peak. When we say "230 V mains", that is the RMS value; the actual peak voltage is about 325 V.'], ['question' => 'What is Ohm\'s Law?', 'answer' => "Ohm's Law states that voltage (V) equals current (I) multiplied by resistance (R): V = I × R. It describes the linear relationship between voltage and current in a resistive circuit. This can be rearranged to find any one variable: I = V/R or R = V/I."], ['question' => 'How do millivolts and kilovolts relate to volts?', 'answer' => '1 millivolt (mV) = 0.001 V. 1 kilovolt (kV) = 1000 V. Millivolts are used in electronics (sensor outputs, battery cells). Kilovolts are used in high-voltage transmission lines (typically 11 kV, 33 kV, 66 kV, 132 kV, 400 kV in distribution systems).'], ]" />

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