The electromotive force of a cell is 2V. The potential difference becomes 1.5 V when a resistance of `15 Omega` is added to the two ends of the cell. Determine the internal resistance of the cell and the lost volt.

Explanation

Lost volt=E-V=2-1.5=0.5 V
Current of the external circuit
`=(potential dif ference of the external cir cuit)/(resistance of the external cir cuit )`
`=1.5/15=0.1A`
This is the current flowing through the cell
So, internal resistance of the cell
`r=(lost vol t(lr))/(current(l))=0.5/0.1=5 Omega`