You can multiply the voltage or the current supplied by individual batteries by connecting them together either in series or in parallel. The characteristics of batteries connected in parallel are that total voltage equals the average of the individual battery voltages, total current equals the sum of the individual battery currents, the positive terminal of one battery is connected to the positive terminal of the next, the negative terminal of one battery is connected to the negative terminal of the next, and two connections are made between each adjacent battery.

A series circuit has only one path for current to flow. In a series circuit, current (I) is the same throughout the circuit and is equal to the total voltage (V) applied to the circuit divided by the total resistance (R) of the loads in the circuit. The sum of the voltage drops across each resistor in the circuit will equal the total voltage applied to the 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.

Most households use electricity with a voltage of 110V.

The transistor is the foundation of modern electronic devices. It is made entirely from semiconductor material (making it a solid state device) and can serve many different functions in a circuit including acting as a switch, amplifier, or current regulator. A transistor works by allowing a small amount of current applied at the base to control general current flow from collector to emitter through the transistor.