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Ohm's Law: V = IR. Watt's Law: P = VI = I²R = V²/R. Enter any two values to solve for the others. Series circuits: total R = sum of resistances; current is the same through all. Parallel circuits: 1/R_total = Σ(1/Rᵢ); voltage is the same across all. Safety note: household AC (120V/240V) can be lethal—always follow electrical codes and use qualified electricians for wiring.
Enter any two of voltage (V), current (A), and resistance (Ω). The third is calculated. Power P = V × I.