Calculating change in energy of a particle

[x86]

Homework Statement

An electron moves from an initial location between parallel plates where the electric potential is Vi = 30 V and Vf = 150 V

a) Determine the change in the electrons potential energy

2. Equations
J/C = V = N/C * m

The Attempt at a Solution

a) The electron is naturally moving to a location of higher energy, therefore its potential energy decreases as its kinetic energy increases.

Potential energy change = Ep2 - Ep1 = Vfq - Viq = q(Vf-Vi) = q(120 V) = -1.92 * 10^-17 J.

The sign makes sense to me, since the electron has more potential energy at Vi than Vf.

However, the book says the answer is +1.92*10^-17 J. Can someone help me out with why I am is wrong? Thanks

 

[Fightfish]

Well your book looks like its wrong. Your qualitative reasoning seems correct to me.

 

[rude man]

Are you sure they didn't ask for the change in kinetic energy? Because otherwise I have to agree with your answer as being negative.

 

[x86]

Yes I'm sure they asked for potential energy. I guess the book is wrong. Thanks for confirming this.