When a resistor of `11Omega` is conntected in series with an electric cell, the current flwoing in it is `0.5` A. Instead, when a resistor of `5Omega` is conntected to the same electric cell in series, the current increase by `0.4` A , The internal resistance of the cell is

Explanation

We know `V=i(R+r)=0.5(11+r)+ ………….(1)"`
`V=0.9(5+r)" ………… (2)"`
From `(1)&(2)0.5(11+r)=0.9(5+r)`
`0.5xx11+0.5r=0.9xx5+0.9r`
`5.5xx0.5r=4.5+0.9r rArr 0.4r=1`
`r=2.5Omega`