What is cell potential in an electrochemical cell?
A galvanic cell is set up by generating a redox reaction, whose current is used to do work and the chemical energy is changed to electrical energy. Remember that a full oxidation-reduction reaction can be broken down to two half-reactions, one oxidation (loss of electrons) and one reduction (gain of electrons). There is a transfer of electrons from the anode (oxidation) to the cathode (reduction). There is a driving force that pulls the electrons from the anode to the cathode. This force is the cell potential of the electrochemical cell. It is measured in volts, which is 1 joule of work per Coulomb of charge transferred.
Cell potential can be measured through a voltmeter. A voltmeter draws current through a known resistance. Notice, that a voltmeter is not precise because frictional heating occurs in the wire and uses some of the energy of the cell, so the number we get is actually less than the actual cell potential. It would be ideal to find the cell potential under zero current using a potentiometer. In these conditions, the cell potential has the same magnitude but opposite sign to the voltage of the potentiometer.