Voltage (V) is the electrical potential difference between two points. A voltmeter is used to measure the voltage between two points in a circuit.

All conductors have resistance and the amount of resistance varies with the element.  But, resistance isn't the only consideration when choosing a conductor as the most highly conductive elements like silver and gold are also more expensive and more brittle than slightly less conductive elements like copper. A balance needs to be struck between the electrical qualities of a material and its cost and durability.

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.

Connecting the 10 batteries in series multiplies their voltage while keeping their current the same yielding a 150V 10A configuration. Connecting the 10 batteries in parallel multiplies their current while keeping their voltage the same yieleding a 15V 100A configuration. Using a series-parallel connection, 5 batteries can be connected in series and 5 can be connected in parallel resulting in a 75V 50A configuration.

All conductors have resistance and the amount of resistance varies with the element. In general, metals make the best conductors of electricity and non-metals make the worst conductors of electricity.