Question

A cell of emf E and internal resistance r is connected with a variable external resistance R and a voltmeter showing potential drop V across R. Obtain the relationship between V, E, R and r.

Answer 1

For a cell with EMF (E) and internal resistance r:

V = E − Ir

Sunstituting = `V/R`

Rearranging:

`V(1 + r/R)` = E

V = `(ER)/((R + r))`