What is the function of an immersion heater?

An immersion heater functions specifically to directly heat liquids by being submerged in the fluid, which allows for efficient heat transfer. This type of heater typically consists of a heating element that gets placed within the liquid, ensuring that the heat is delivered directly where it's needed most. By immersing the heating element, the heater can rapidly elevate the temperature of the surrounding fluid, making it suitable for applications like heating water in tanks, boilers, or industrial processes.

The other choices do not accurately describe the role of an immersion heater. Circulating air relates to different types of heating systems, while cooling gases and regulating temperatures of solid materials involve different mechanisms and equipment that operate under different principles than immersion heating.