A resistive grid includes a frame and at least one resistive element. The frame has a first frame end and a second frame end opposite the first frame end. The first frame end and the second frame end are joined by frame sides. The first frame end has a first length that is shorter than a second length of the second frame end. The at least one resistive element extends between the first frame end and the second frame end. The at least one resistive element has a first portion proximate the first frame end, and a second portion proximate the second frame end. The first portion is configured to have one or both of decreased heat generation or decreased electrical resistance relative to the second portion.