When a resistance R is across a cell, the voltage across the terminals of the cell is reduced to two-third of its normal value. The internal resistance of t...

When a resistance R is across a cell, the voltage across the terminals of the cell is reduced to two-third of its normal value. The internal resistance of the cell is

Answer Details

IR = $\frac{2}{3}$ I(R + r)

r = $\frac{1}{2}$R