Question

A wire of resistance 0.25 ohm is first connected to a cell of internal resistance 0.50 ohm and then connected to a combination of 10 such cells in parallel. The ratio of currents in the two cases is

• A. 1 : 2
• B. 3 : 4
• C. 1 : 5
• D. 2 : 5

Answer 1

The correct option is D 2 : 5

Case 1 :

$I=\frac{E}{R+r}$

$I=\frac{E}{0.75}$

Case 2 :

$E_{eff}=E$

$r_{eff}=\frac{r}{10}$

$I^1=\frac{E}{r+\frac{r}{10}}=\frac{E}{0.25+0.05}=\frac{E}{0.30}$

$\frac{I}{I^1}=\frac{2}{5}$