Voltage Calculator
Calculate voltage in circuits
Frequently Asked Questions
What is voltage and how is it measured?
Voltage (V) is the electrical potential difference between two points, measured in volts. It drives current through a circuit, like water pressure in a pipe. Common voltages: USB 5V, car battery 12V, household outlet 120V (US) or 230V (EU).
How do I calculate voltage using Ohm's Law?
Voltage = Current × Resistance: V = I × R. If 2 amps flow through a 50-ohm resistor: V = 2 × 50 = 100 volts. The calculator also derives voltage from power: V = P/I or V = √(P×R).
What is the difference between AC and DC voltage?
DC (Direct Current) flows in one direction at constant voltage (batteries, USB). AC (Alternating Current) reverses direction periodically (household power). AC voltage is specified as RMS: 120V RMS has a peak of 170V.
How do voltage dividers work?
A voltage divider uses two resistors to reduce voltage: V_out = V_in × R₂/(R₁+R₂). To get 3.3V from 5V: choose R₁=5.1kΩ and R₂=10kΩ, giving V_out = 5 × 10/(5.1+10) = 3.31V. The calculator finds optimal resistor values.
What is voltage drop and why does it matter?
Voltage drop is the reduction in voltage along a wire due to resistance. Long wire runs or undersized cables cause significant drops. The NEC recommends maximum 3% drop for branch circuits. For 100ft of 14AWG at 15A: drop ≈ 4.8V (4%).