A potentiometer is basically

A transfer instrument employed in the standardization of a polar type $$a.c$$ potentiometer is ______

The primary current in a current transformer is dictated by

In $$d.c.$$ potentiometer measurements, a second reading is often taken after reversing the polarities of the $$s.c.$$ supply and the unknown voltage, and the average of the two readings is taken. This is, with a view to eliminate the effects of