Question

By a cell current of 0.9a floes through 2ohm and 0.3a through 7 ohm. The internal resistance of the cell is

Answer 1

Answer:

$i = \frac{v}{r} \\ 0.9 = \frac{v}{2 + r} ......(1) \\ 0.3 = \frac{v}{7 + r} ......(2) \\ divide \: 1 \: by \: 2 \\ 3 = \frac{7 + r}{2 + r} \\ or \: 6 + 3r = 7 + r \\ or \: 2r = 1 \\ or \: r = 0.5 \: ohm$