Question

Explain why is the potential difference across the terminals of a cell more in an open circuit and reduced in a closed circuit?​

Answer 1

When the electric cell is in a closed circuit the current flows through the circuit. ... 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

Answer 2

no ideal battery or cell has no internal resistance, i.e., r=0.

So there is no voltage drop across the materials in side the battery, When it is connected in a circuit with some external elements.

When a battery is not connected in a circuit or it is open, then there is no current passing through it. So the emf the potential difference observed by measurement.

When a battery has an internal resistance r, and it is connected through a circuit, there is a current I flowing in the circuit. Hence, there is a voltage drop across this internal resistance.

So P.d. across battery=emf−r.I

$itzDopeGirl$❣