My question relates to the postie and negative signs. First I set up an equation to solve: 9600J = -8.0 x 10² x V When I solve, I have - 12 V. But the answer is +12 V. Why did the 9600J become negative in the algebraic equation?

Example 17.3 A battery-powered lantern is switched on for 5.0 min. During this time, electrons with total charge 8.0 x 102 C flow through the lamp; 9600J of electric potential energy is converted to light and heat Through what potential difference do the electrons move? Strategy The equation AUE =q AV relates the change in electric potential energy to the potential difference. We could apply the equation to a single electron, but since all of the electrons move through the same potential difference, we can let q be the total charge of the electrons and AU be the total change in electric potential energy. AU Solution AV = -9600 J =+12 V -8.0 x 102 C