In a arrangement, 3n cells of emf `epsilon` and internal resistance r are connected in series. Out of 3n cells polarity of n cells is reversed. Current in the circuit is

Options

A. `(2 epsilo)/(r)`
B. `(2 epsilon)/(3r)`
C. `(epsilon)/(3r)`
D. `(epsilon)/(r)`

Answer

C

Explanation

`(1)/(f)=((3)/(2)-1)((1)/(15))`
f=30 cm
`(1)/(v)+(1)/(36)=(1)/(30)rArr (1)/(v)=(1)/(30)-(1)/(36)=(1)/(180)`
`v = 180` cm.