Question

The terminal voltage of a battery is 5.0V when 0.55A current is drawn from it, whereas the terminal voltage is 5.7V when a current of 0.180A is drawn. The emf of the battery is?

The formula I used was
V_(ab) = Emf - I*r
First finding the r by taking the differences of voltage and the currents, which then for r I got is .7V/.37A = 1.89 Ohms. and then inserting it back to the formula above I get the Emf to be 1.39. Which I am not sure if it is right. Any help will be appreciated.

Answer 1

emf - (internal resistance * current) = terminal voltage

(Ri * .55) + 5.0 = (Ri * .18) + 5.7

emf - (1.9 * .55) = 5.0

Answer 2

Ah I see, thank you so much.