A potentiometer is an accurate and versatile device to make electrical measurements of E.M.F. because the method involves :
cells
potential gradients
a condition of no current flow through the galvanometer
a combination of cells, galvanometer and resistances
As we discussed in
Potentiometer -
It is a device used to measure e.m.f of a given cell and to compare e.m.f's of cells
- wherein
It is also used to measure internal resistance of given cell
None
Because the method involves a condition of no current flow through the galvanometer the device can be used to measure P.D internal resistance of a cell and compare emf's of two sources
Option 1)
cells
This option is incorrect
Option 2)
potential gradients
This option is incorrect
Option 3)
a condition of no current flow through the galvanometer
This option is correct
Option 4)
a combination of cells, galvanometer and resistances
This option is incorrect