@cos90 you're correct, it can be seen, though at very low voltage levels (at least with regards to nominal). If you think of a three phase XFMR, the flux is coupled between the legs of the core simply due to the design (usually either 4 or 5 legged to mitigate heating, as
@PwrEngr alluded to).
For modern appliances/heat pumps/etc., most have sensors that limit them from turning on when low voltage is present (usually on the order of 60-70 % of nominal and ranging from a few cycles up to dozens of seconds under these conditions). A cursory investigation would lead you to consider that only resistive, unsensored circuits will be 'on'. Further investigation would indicate that these consumers will experience what PwrEngr mentioned, flickering lights and brownouts.
I don't foresee that you would see this exact scenario on the exam, however, I presented this for pure understanding purposes, and to illustrate how real-world scenarios apply on a power system.
I'll post more scenarios as time permits and as I think them up.
Here's a fairly simple one, but it may be of use to someone reading this board, what purpose do fuses over a cap bank serve? Seems intuitive and, for the most part, it is; but it is a fundamental question that can trigger someone's thought process when working with capacitors, reactive power, PF correction and the concept of "negative" VARs.
