All conductors have resistance and the amount of resistance varies with the element. Metals exhibit increased resistance (and, therefore, lower conductivity) as their temperature increases.

In a parallel circuit, each load occupies a separate parallel path in the circuit and the input voltage is fully applied to each path. Unlike a series circuit where current (I) is the same at all points in the circuit, in a parallel circuit, voltage (V) is the same across each parallel branch of the circuit but current differs in each branch depending on the load (resistance) present.

Connecting the 4 batteries in series multiplies their voltage while keeping their current the same yielding a 48V 25A configuration. Connecting the 4 batteries in parallel multiplies their current while keeping their voltage the same yieleding a 12V 100A configuration. Using a series-parallel connection, 2 batteries can be connected in series and 2 can be connected in parallel resulting in a 24V 50A configuration.

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

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.