Resistors are used to limit voltage and/or current in a circuit and can have a fixed or variable resistance.  Variable resistors (often called potentiometers or rheostats) are used when dynamic control over the voltage/current in a circuit is needed, for example, in a light dimmer or volume control.

Current is the rate of flow of electrons per unit time and is measured in amperes (A). A coulomb (C) is the quantity of electricity conveyed in one second by a current of one ampere.

Connecting the 10 batteries in series multiplies their voltage while keeping their current the same yielding a 90V 20A configuration. Connecting the 10 batteries in parallel multiplies their current while keeping their voltage the same yieleding a 9V 200A configuration. Using a series-parallel connection, 5 batteries can be connected in series and 5 can be connected in parallel resulting in a 45V 100A configuration.

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.

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.