To get maximum current through a resistance of `2.5Omega,` one can use m rows of cells, each row having n cells. The internal resistance of each cell is `0.5 Omega` what are the values of n and m, if the total number of cells is 45.

Options

A. m=3, n=15
B. m=5,n=9
C. m=9, n=5
D. m=15, n=3

Answer

A

Explanation

The current l will be maximum, if
if `" " mR=nr` or `R=(nr)/(m)`
Here, mn = 45 `" "` (given) …(i)
and `m xx 2.5=n xx0.5`
or n = 5 m …(ii)
From Eqs. (i) and (ii), we have
`5m^(2)=45` or `m^(2)=9 rArr m =3`
`therefore " " n = 15`