Some electrical formulas include Ohm's Law, which states that voltage equals current times resistance, and the formulas associated with Kirchhoff's Laws, one of which states that the sum of all voltages must add up to 0. Kirchhoff's formulas only apply to circuits, while Ohm's Law and formulas are generally applicable.
Ohm's Law is expressed mathematically in a number of different ways, with formulas that lend themselves better to finding voltage, resistance or current, as the case may be. All of these formulas are, however, mathematically equivalent. One important formula based on Ohm's Law is the power formula, which states that power is equivalent to voltage times current.
Kirchhoff's Laws are fundamental to circuit theory and design. One states the sum of all currents leaving a node in an electrical network always equals 0. The second of Kirchhoff's Laws states that the sum of all voltages across a closed circuit also equals 0. The formulas for these laws are often used by electrical engineers to analyze electrical nodes and build accurate models of circuits.