What is a method used to heat metals effectively?

The most effective method for heating metals in the context presented is through electrical resistance heating. This method involves passing an electric current through a metal, causing it to heat up due to the resistance the metal exhibits to the flow of electricity. The heat produced can be easily controlled by adjusting the current, allowing for precise temperature management that is often essential in various industrial applications, such as forging, soldering, or metal casting.

In contrast, using an open flame can lead to uneven heating and is less controllable. It also poses risks associated with gas and combustion. Measuring specific heat with a calorimeter, while useful for understanding thermal properties, does not actively heat the metal. Exposing metals to sunlight might not be practical or efficient, as it relies on environmental conditions and lacks the intensity and control offered by other methods.