No matter how high you heat your toast or kettle, there is an upper limit to how fast that heat can be conducted through the medium (bread or water).

At a certain limited, you either just char the surface of the bread, or vaporize the water in contact with the heating element, while the inner bread or water still remains ambient.

As water is liquid, that high of a temperature WOULD result in a faster boiling time, but it would be a violent process. Not something safe for the kitchen.