Direct current flows in only one direction in a circuit, from the negative terminal of the voltage source to the positive. A common source of direct current (DC) is a battery.

A semiconductor is a material that has a limited ability to conduct electrical current with conductivity between that of an insulator and that of a conductor. Silicon, a cheap and abundant material, is the most used semiconductor material although other materials are used in the electronics components made from semiconductors. The primary advantages of a semiconductor over a conductor is that the conductivity of a semiconductor can be varied under an external electrical field giving engineers precise control over complex circuits and, unlike conductors like metals, a semiconductor's conductivity increases with increased temperatures.

Resistance is opposition to the flow of current and is measured in ohms (Ω). An ohmmeter is used to measure the amount of resistance at a certain point in a circuit.

A diode allows current to pass easily in one direction and blocks current in the other direction. Diodes are commonly used for rectification which is the conversion of alternating current (AC) into direct current (DC). Because a diode only allows current flow in one direction, it will pass either the upper or lower half of AC waves (half-wave rectification) creating pulsating DC. Multiple diodes can be connected together to utilize both halves of the AC signal in full-wave rectification.

Electrons flow from an area of high concentration to an area of low concentration. A high voltage indicates a high concentration of electrons that creates a greater potential for electron flow than a low voltage. When applied to a load, voltage creates electricity and potential difference is the measure of voltage at a specific location in an electrical circuit.