Which is smaller : terminal potential difference for EMF of a cell and why?
Answers
Answer:
Terminal potential difference is the potential difference between the two electrodes of the cell in a closed circuit (ie when current is drawn from the cell).
Terminal potential difference is less than emf because when the cell is sending charge around the closed circuit, the electrolyte between cell electrodes bearing some finite resistance(we call it internal resistance), opposes the flow of ionic current inside the cell due to which there is some potential drop inside the cell (equal to Ir). Therefore a part of electromotive force is lost inside the cell, the remaining electromotive force(called terminal p.d) is equal to the potential drop across external resistor (IR)
In case when no current is drawn from the cell (in open circuit), the terminal p.d. is equal to the emf...