What is the main function of a magnetizer in a toolkit?

The main function of a magnetizer in a toolkit is to magnetize and demagnetize tools. This is particularly useful in situations where magnetic tools can enhance efficiency and effectiveness during electronic repairs or assembly tasks. For instance, a screwdriver that is magnetized can easily hold screws in place, which is especially helpful in tight or awkward working conditions where precision is paramount. Additionally, demagnetizing tools can be necessary when working with sensitive electronic components, as magnetic interference could affect their functionality or damage them.

The other options do not align with the capabilities of a magnetizer. Changing the size of screws, cutting wires, or measuring electrical current are functions that would require different tools or equipment altogether, as these tasks cannot be performed by a device designed specifically for magnetizing or demagnetizing.