Question

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

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

Answer 1

Answer: (A)

m= 3, n = 15

Answer 2

R = 2.5 Ω, r = 0.5 Ω

no. of rows = m , no of cells in each row = n

i = $\frac{nE}{R + nr/m}$ total cells ⇒ mn = 45

for max. current ;R = nr/m, mR = nr

n = 5m , 5m² = 45, m = 3, n = 15