Electrical wires have a certain amount of resistance per foot. A longer wire means more resistance and a greater voltage drop.

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.

Insulators have valence shells that are more than half full of electrons and, as such, are tightly bound to the nucleus and difficult to move from one atom to another.

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. The three most common types of batteries are dry cell (used in small devices like TV remotes), wet cell (used for cars), and deep-cycle (storage batteries used primarily for backup and emergency power).

Electrical power is measured in watts (W) and is calculated by multiplying the voltage (V) applied to a circuit by the resulting current (I) that flows in the circuit: P = IV. In addition to measuring production capacity, power also measures the rate of energy consumption and many loads are rated for their consumption capacity. For example, a 60W lightbulb utilizes 60W of energy to produce the equivalent of 60W of heat and light energy.