You can multiply the voltage or the current supplied by individual batteries by connecting them together either in series or in parallel. The characteristics of batteries connected in series are that total voltage equals the sum of the individual battery voltages, total current equals the average of the individual battery currents, the positive terminal of one battery is connected to the negative terminal of the next, and one connection is made between each adjacent battery.

Connecting the 4 batteries in series multiplies their voltage while keeping their current the same yielding a 60V 10A configuration. Connecting the 4 batteries in parallel multiplies their current while keeping their voltage the same yieleding a 15V 40A configuration. Using a series-parallel connection, 2 batteries can be connected in series and 2 can be connected in parallel resulting in a 30V 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.

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.

A fuse is a type of low resistance resistor that stops current flow in a circuit in response to a larger than intended electric current flow. Using a fuse with a higher current rating than required by a circuit is less safe as it could potentially allow overcurrent and risk a fire or heat-related equipment damage.