Electric Potential vs Electric Potential Energy

In summary, the problem involves a released electron in an external electric field, moving upwards a certain distance. The change in electric potential energy is calculated using the formula -(qEdcos(theta)), and it is found that the energy has decreased. However, when dividing by the charge of the electron, which is negative, the resulting change in electric potential is positive. This may seem counterintuitive, but it is because the charge of the electron is negative, resulting in a change in potential with the opposite sign of the change in energy. If the charge were positive, the change in potential would have the same sign as the change in energy.
  • #1
Alex Hughes
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So in my physics textbook a problem is stated. We are given an external electric field directed downwards of 150N/C. We are then told that an electron is released in the electric field and it moves upwards 520m. Finally we are asked to calculate the change in electric potential energy of the released electron and through what potential change does it move. I understand the math behind the problem, the amount of work = -(change in electric potential energy). Since work is (force * distance) and in an electric field the force is (q*E), to find the change in electric potential energy it becomes -(qEdcos(theta)). They find the answer and the change in electric potential energy of the electron is said to have DECREASED by a certain amount. Then to find the change in electric potential, they divide by the charge of the electron and say the electric force does work to move the electron to a HIGHER potential. That's where I'm confused. How can the electric potential energy decrease, but move to a higher potential. Am i not understanding the definition of each term? Please somebody help, I'm so confused. Thanks.
 
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  • #2
And like I said, I understand the math behind it, I'm just trying to understand it conceptually. Obviously the potential is higher because the electric potential energy is negative and you divide by the charge of an electron which is also negative, giving you a positive value. But conceptually it doesn't make sense to me that a LOSS in energy results in a HIGHER potential.
 
  • #3
Since the charge is negative the change in potential energy will always have the opposite sign of the change in potential.
 
  • #4
Dale said:
Since the charge is negative the change in potential energy will always have the opposite sign of the change in potential.
So, if the charge was positive, the change in potential energy would have the same sign as the change in potential?
 
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  • #5
Alex Hughes said:
So, if the charge was positive, the change in potential energy would have the same sign as the change in potential?
Yes, exactly
 

1. What is the difference between electric potential and electric potential energy?

Electric potential is a measure of the potential energy per unit charge at a certain point in an electric field. It is a scalar quantity and is measured in volts (V). On the other hand, electric potential energy is the potential energy that a charged object possesses due to its position in an electric field. It is a scalar quantity and is measured in joules (J).

2. How are electric potential and electric potential energy related?

Electric potential and electric potential energy are related by the equation V = U/q, where V is the electric potential, U is the electric potential energy, and q is the charge. This means that electric potential energy is directly proportional to electric potential.

3. Can electric potential and electric potential energy be negative?

Yes, both electric potential and electric potential energy can be negative. This occurs when the electric field is directed opposite to the direction of the force on a positive charge. In this case, the electric potential is negative because it takes work to move a positive charge from a point of higher potential to a point of lower potential. The electric potential energy is also negative because the charge has lost potential energy as it moves in the opposite direction of the electric field.

4. How do changes in distance and charge affect electric potential and electric potential energy?

The electric potential is directly proportional to the distance from the source charge and inversely proportional to the magnitude of the charge. This means that as the distance between the source charge and the point in the electric field increases, the electric potential decreases. As the magnitude of the charge increases, the electric potential also increases. Similarly, the electric potential energy is directly proportional to the distance from the source charge and the magnitude of the charge. As the distance increases, the electric potential energy decreases, and as the magnitude of the charge increases, the electric potential energy also increases.

5. What is the unit of measurement for electric potential and electric potential energy?

The unit of measurement for electric potential is volts (V), which is equivalent to joules per coulomb (J/C). The unit of measurement for electric potential energy is joules (J), which is equivalent to newton-meters (N*m).

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