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.

Connecting the 8 batteries in series multiplies their voltage while keeping their current the same yielding a 48V 5A configuration. Connecting the 8 batteries in parallel multiplies their current while keeping their voltage the same yieleding a 6V 40A configuration. Using a series-parallel connection, 4 batteries can be connected in series and 4 can be connected in parallel resulting in a 24V 20A configuration.

An amplifier is a device that takes a small input signal and creates a larger output signal. This makes it most similar to a step-up transformer which takes a smaller input voltage and creates a larger output voltage.

Voltage (V) is the electrical potential difference between two points. Electrons will flow as current from areas of high potential (concentration of electrons) to areas of low potential. Voltage and current are directly proportional in that the higher the voltage applied to a conductor the higher the current that will result.

Electricity is delivered from power stations to customers as AC because it provides a more efficient way to transport electricity over long distances. A line drop is a decrease in voltage between two points on an electrical transmission line due to resistance in the line. A lower current and higher voltage across the line will help compensate for the line drop.