# Electron moving from point A to B. electron potential higher?

1. Aug 17, 2011

### rcmango

1. The problem statement, all variables and given/known data

An electron , influenced only by electric fields and forces, moves from A to B. When it reaches B, its speed is higher than it was at A. Is the electric potential higher at A or at B?

2. Relevant equations

3. The attempt at a solution

So as the electron gets closer to B, the potential rises. So as the potential rises, the electron gets closer, the EPE, it also rises. As the EPE increases the kinetic energy decreases for the electron and it begins to slow down, the energy is never lost, it is transferred. So the electric potential would be great at B?

2. Aug 17, 2011

### kuruman

Correct.
How could the kinetic energy decrease when the problem clearly states that the speed of the electron increases when it moves from A to B? Sounds to me that potential energy is traded for a gain in kinetic energy.

3. Aug 17, 2011

### kuruman

Correct.
How could the kinetic energy decrease when the problem clearly states that the speed of the electron increases when it moves from A to B? Sounds to me that potential energy is traded for a gain in kinetic energy.

What is the sign of the change in electric potential and what is the sign of the change in electric potential energy?

4. Aug 17, 2011

### rcmango

Okay, I realized that I missed something in the question where it said it was gaining speed.

So, as the electron is approaching B, its potential is rising, as the potential is rising so is the Electric potential energy, it is also rising. The electric Potential is higher at B, how can I prove this though? I'm not sure how?

5. Aug 17, 2011

### SammyS

Staff Emeritus
Is the electric charge of an electron positive, or is it negative?

What's the definition of electric potential?

6. Aug 17, 2011

### rcmango

the electron charge is negative.

Electric potential: measure of work required by an electric field to move a charge. (Voltage)

7. Aug 17, 2011

### SammyS

Staff Emeritus
What is your textbook's definition of Electric Potential ?

8. Aug 18, 2011

### rcmango

The textbook explanation is simply that electric potential is equal to electric potential energy per unit charge.

9. Aug 18, 2011

### SammyS

Staff Emeritus
As the electron approaches B its speed is higher than it was at A ... so does the Kinetic Energy increase from A to B or does it decrease?

Using that answer & conservation of energy, is the electron's Potential Energy higher -- or is it lower -- at B than at A? In other words, is Δ(PE) positive or negative in going from A to B ?

If Electric Potential, V, = PE/Qelectron , then how is Δ(V) related to Δ(PE) ?