Question

The n rows each containing m cells in series are joined in parallel. Maximum current is taken from this combination across and external resistance of 3ohm resistance. If the total number of cells used are 24 and internal resistance of each cells is 0.5ohm then

• A. $m=8,n=3$
• B. $m=6,n=4$
• C. $m=12,n=2$
• D. $m=2,n=12$

Answer 1

Answer: (C)

Total cells $=m\times n=24$..... (i)
For maximum current in the circuit
$R=\frac{mr}{n}$
$\Rightarrow 3=\frac{m}{n}\times \frac{1}{2}$
$\Rightarrow m=6n$.. (ii)
On solving equation (i) and (ii) we get
$n=2,m=12$