Capacitors store electricity and are used in circuits as temporary batteries. Capacitors are charged by DC current (AC current passes through a capacitor) and that stored charge can later be dissipated into the circuit as needed. Capacitors are often used to maintain power within a system when it is disconnected from its primary power source or to smooth out or filter voltage within a circuit.

Connecting the 4 batteries in series multiplies their voltage while keeping their current the same yielding a 60V 5A configuration. Connecting the 4 batteries in parallel multiplies their current while keeping their voltage the same yielding a 15V 20A configuration. Using a series-parallel connection, 2 batteries can be connected in series and 2 can be connected in parallel resulting in a 30V 10A configuration.

Electricity is delivered from power stations to customers as AC because it provides a more efficient way to transport electricity over long distances. Most households use electricity with a frequency of 60Hz.

A schematic is the proper name for a drawing of an electric or electronic circuit.

Circuits containing transistors are packaged into integrated circuit chips that allow encapsulating complex circuit designs (CPU, memory, I/O) for easier integration into electronic devices and machines.