“can you please explain about emf and PD of a cell?”
EMF stands for electromotive force.
EMF of a cell is equal to the potential difference between the two terminals of a cell when no current is drawn from it.
Pd (potential difference) between any two points on a circuit is defined as the work done per unit charge in carrying a positive test charge from one point to the other. With reference to a cell, the potential difference between the terminals of a cell when a current is drawn from it is called terminal voltage.