What is the primary function of a rectifier in electrotherapy?

The primary function of a rectifier in electrotherapy is to change alternating current (AC) into direct current (DC), which is often referred to as galvanic current. This is crucial because different types of currents serve various therapeutic purposes in electrotherapy treatments. Direct current is particularly beneficial for procedures like iontophoresis, where medications are pushed into the skin using an electric current, as well as in other treatments focused on stimulating and repairing tissues.

When AC is rectified into DC, the current becomes suitable for these specific therapeutic applications. The other options do not align with the role of a rectifier. For example, amplifying the current is typically achieved through different electronic components, while cooling the skin and measuring skin resistance involve different processes not related to current conversion in electrotherapy devices. Thus, the rectifier's key role in producing an effective treatment modality by converting AC to galvanic current is fundamental for successful outcomes in electrotherapy.