A cell supplies a current of 0.9 A through a `2Omega` resistor and a current of 0.3 A through a `7Omega` resistor. The internal resistance of the cell is

Options

A. `1.2Omega`
B. `2.0Omega`
C. `0.5Omega`
D. `1.0Omega`

Answer

C

Explanation

`I_(1)=(E)/(2+r)=0.9` . . (i)
`I_(2)=(E)/(7+r)=0.3` . . . (ii)
(i) and (ii) gives `(7+r)/(2+r)=(0.9)/(0.3)`
or, `2.1+0.3r=1.8+0.9r`
`implies0.6r=0.3impliesr=0.5Omega`
`therefore`Internal resistance of the cell=`0.5Omega`.