Question

Explain why is the p.d. across the terminals of a cell is more in an open circuit and reduced in a closed circuit.

Answer 1

When the electric cell is in a closed circuit, some current flows through the circuit. There is a fall of potential across the internal resistance of the cell. So, the p.d. across the terminals in a closed circuit is less than the p.d. across the terminals in an open circuit by an amount equal to the potential drop across the internal resistance of the cell.