Electrical Fundamentals
Voltage, current, and resistance are the three quantities behind every electrical calculation on this site. Ohm's Law relates them, and most other formulas build on this relationship.
Voltage
Voltage is the electrical pressure that pushes current through a circuit, measured in volts (V). It's the difference in electrical potential between two points.
Current
Current is the rate of flow of electric charge through a conductor, measured in amps (A). More current means more charge moving past a point each second.
Resistance
Resistance is a conductor's opposition to current flow, measured in ohms (Ω). Higher resistance means more voltage is needed to push the same current through.
How they relate
Ohm's Law (V = I × R) ties voltage, current, and resistance together: knowing any two lets you calculate the third. Most of the calculators in this category are direct applications of this relationship.