Question

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

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

Answer 1

Answer: (A)

$R=2.5\Omega \, , \, r=0.5\Omega$
no of rows $=m, \, $ no of columns in each row $=n$
$i=\frac{n E}{R + n r / m}$ total cells $\Rightarrow mn=45$
for max. current; $R=nr/m, \, mR=nr$
$m=3, \, n=15$