How is current measured in direct current?

In the context of measuring direct current, the correct measure is in milliamperes. Amperes (or amps) represent the flow of electric current, and while they are a standard unit of measurement for larger currents, milliamperes are used to identify smaller currents that are common in devices like those used in electrology, laser, and IPL equipment.

This distinction is significant because many cosmetic and medical devices operate using low levels of current, which are more accurately represented in milliamperes to allow for precise measurement and control. Using milliamperes provides a clearer understanding of the current levels being used in treatments, ensuring both effective and safe operation.

The other options involve different measurements that do not pertain directly to current flow: volts measure electrical potential, and watts measure power, which is a function of both current and voltage. Thus, for measuring direct current in the specific applications relevant to electrology, laser, and IPL practices, milliamperes is the appropriate choice.