My A-level Physics is long distant, and I'm not sure would help with this question.
We have a shower that's connected directly to mains electricity (220V, with a 40A breaker. The shower itself is rated at 35A). The shower has two heat settings (Winter and Summer) which basically change the level of direct heating. The temperature is more realistically controlled by the tap/faucet which controls the water. This is the norm here in Brazil.
The problem is that after 30 or so minutes of using the shower (say, a couple of people using the shower after each other) the breaker trips. We were told by an electrician that this is caused by the wiring being insufficient for the load from the shower, and the wires are overheating (although thankfully not sufficiently to melt the insulation and short circuit). This I believe.
He also said that because the wiring isn't sufficiently rated the shower can't heat as well as it should. And that's my question, is that really true? Can wiring of a smaller dimension limit the current that flows to the shower and reduce its capability to heat?