Electricity Water Analogy
When trying to understand how electricity works, try using the water analogy. In many ways electricity behaves very much like water. We even say the electricity "flows" through wires. Electricity flows from one battery terminal to the other and through all the wires between them just like the fluid in a hydraulic (liquid) system. The fluid pump acts as the battery or alternator. The fluid pump puts the fluid under pressure. How much pressure depends on the pump's power. The fluid delivers energy to components and makes them work. If you have a large hydraulic ram, you need a large pipe to feed in the power. For smaller rams a smaller pipe will do. The same amount of pressure is delivered (usually between 1,000 and 3,000 psi). Here's a snippet from Matt Stong's book, "Custom Auto Wiring & Electrical":
The higher the pressure, the smaller the ram can be so the equipment can be a little lighter and the fluid volume will be less, but the hoses are still sized to the flow, just like electrical systems must be. It is much the same for electricity; 24 volts can deliver more power than 12 volts, but automotive vehicles are all 12 volts to save weight and cost. The pressure (voltage) in any given circuit is the same no matter what the pipe (wire) size and it delivers energy to the components such as the starter motor so they can do their work. But if you are delivering 1,000 volts through a large wire with high amperage, it can do far more work than 12 volts through a 16-gauge wire.
It can also do far more damage if the circuits are not designed to handle its potential. Liquid flow consists of two components - pressure and volume. With electricity, the "pressure" is voltage and "volume" is amperage. The battery provides the voltage (pressure) and the wires the amperage (volume). The more electricity you need for a component, the fatter the wire you need to feed it. If a pipe is not big enough it will explode. If a wire is not big enough it will also fail, generally by burning up.