negative emf

How Do You Solve EMF Problems? Source: en.wikipedia.org. varepsilon = frac {E}{Q} varepsilon = I (R+r) varepsilon = IR + Ir. varepsilon = V + Ir. Using the formula: varepsilon = V + Ir. How do you solve EMF? The emf is equal to the work done on the charge per unit charge (ε=dWdq) when