Question

20 cells each having emf 10 V and internal resistance $1\Omega$ are connected in 4 parallel rows of five each. Find the maximum current obtained when these cells are connected to a $10\Omega$ external resistance.

• A. 0.44 A
• B. 4.4 A
• C. 14.4 A
• D. 7.07 A

Answer 1

Answer: (B)

4.4 A

Answer 2

The battery consists of 4 parallel rows, each containing 5 series cells.

1. Calculate the EMF of one row: $E_{row} = 5 \times 10V = 50V$. Since rows are in parallel, $E_{eq} = 50V$.
2. Calculate the internal resistance of one row: $r_{row} = 5 \times 1\Omega = 5\Omega$.
3. Calculate the equivalent internal resistance of 4 parallel rows: $r_{eq} = r_{row} / 4 = 5\Omega / 4 = 1.25\Omega$.
4. Apply Ohm's Law: $I = E_{eq} / (R + r_{eq}) = 50V / (10\Omega + 1.25\Omega) = 50V / 11.25\Omega \approx 4.44A$.