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## Homework Statement

two identical cells of emf E and internal resistance r are connected in series.

a 7 ohm resistor is connected across the combination and draws a current of 0.333A.

the two cells are now connected in parallel; the 7 ohm resistor now draws a current of 0.375A from the combination.

calculate the emf and internal resistance of the cells.

## Homework Equations

E - Ir = IR

Sum of potential differences in a closed loop = 0

Current entering a junction = current leaving a junction

## The Attempt at a Solution

i managed to get one equation from the series circuit:

2(E - 0.333r) = 0.333 x 7

and an equation for the parallel circuit:

E - 0.1875r = 0.375 x 7

but this didn't give the correct answers from the book, which says that E = 1.5 and r = 1