On/off controllers do not provide steady __________ current or voltage to regulate the process.

The correct choice is that on/off controllers do not provide steady variable current or voltage to regulate the process. On/off controllers function by switching the output fully on or fully off, rather than adjusting the output continuously. This means that they are not designed to maintain a steady level of variable current or voltage, which is crucial for processes that require precise control.

In contrast to systems that use variable outputs to finely tune the process's conditions, on/off controllers typically create a situation where the controlled variable oscillates between high and low states. While this can effectively maintain a desired set point within certain limits, it lacks the precision and smoothness offered by variable control systems. Thus, the essence of the on/off controller's operation inherently excludes the delivery of a steady, variable output to the process.