What is the output of a single phase rectifier relative to its input?

In a single-phase rectifier, the output voltage is typically less than the input voltage due to the rectification process and the inherent losses associated with it. The output voltage depends on the configuration of the rectifier (e.g., half-wave or full-wave) and the load it is supplying.

For a full-wave rectifier, while the output voltage can be higher than that of a half-wave rectifier, it is still generally around 0.9 times the input when considering the average output. This is due to the transformation from alternating current (AC) to direct current (DC), where the shape of the waveform changes and energy is lost in the conversion process.

With the choices presented, 0.9 times the input is a standard expectation for average output in many configurations, making it the most reasonable answer in this context. The values higher than this (1.0, 1.2) do not reflect typical rectifier behavior, and while you can achieve a peak output that may approach the input, the average output for practical purposes yields around 0.9 times the input.