Voltage (V): the electrical force that pushes charge through a circuit; measured in volts. Current (I): the flow of electrical charge through a conductor; measured in amperes. Resistance (R): the opposition to the flow of current; measured in ohms. Circuit: a complete path through which electricity can flow. Open circuit: a break in the circuit; no current flows. Short circuit: an unintended path with very low resistance; dangerous. Multimeter: an instrument that measures voltage, current, and resistance. Breadboard: a reusable platform for building temporary circuits without soldering. LED: light emitting diode; emits light when current flows through it.

DMM modes: DC voltage (V with a straight line) for batteries and power supplies — red probe to positive, black to common. AC voltage (V with a wavy line) for outlets. DC current (A with a straight line) — break the circuit and insert the meter in series. Resistance (Ω) — component must be isolated from power. Continuity (beep symbol) — beeps when resistance is under about 30 ohms.