Simple DC circuits — original sample notes

Ohm's law is V = I × R: voltage equals current times resistance. Voltage is measured in volts (V), current in amperes (A), and resistance in ohms (Ω). A 6-ohm resistor connected to a 12-volt supply carries 2 amperes. Two 6-ohm resistors in series have a total resistance of 12 ohms, so the same 12-volt supply produces 1 ampere. Two 6-ohm resistors in parallel have an equivalent resistance of 3 ohms; the total current from a 12-volt supply is 4 amperes. Each parallel branch carries 2 amperes. Electrical power is P = V × I. The single 6-ohm resistor using 12 volts and 2 amperes dissipates 24 watts. These examples assume ideal wires and a constant-voltage supply.