The most basic elements of electricity are volts (force) and ohms (resistance).
amps = volts / ohms watts = volts * amps watt-hours = watts * time
Bigger wire = less resistance, generally. So to increase amperage (and thus power), you need bigger wire. But resistance turns power into heat, so if you're trying to shove more power through, waste heat rises. Eventually, it can melt the solder joints that hold circuits together (solder is a very soft lead alloy with a low melting point). Meanwhile, too much power can easily fry the silicon of actual computer chips, and excess heat can cause other problems.