Question

why is no power consumed from the circuit containg unknown emf when a potentiometer is used to measure the unknown emf?​

Answer 1

There is no power consumed as the emf of cell is measured directly.

• Potentiometer utilizes equilibrium or null state when no current passes through the circuit, hence the e.m.f. of the cell is directly measured.
• A potentiometer is used to calculate the emf of a cell, since no current flows in a potentiometer test. Thus a null method of measuring potential difference is used so that no current is drawn from the source to be measured when an equilibrium is achieved and the measurement is taken.