Q: The electron-volt (eV) is a unit of energy commonly used in atomic physics. How much energy in joules is 1 eV?

$$1.6 \times 10$$^{-19}$$~\text{J}$$

Question 1

A positive charge is released from rest in a uniform electric field between two parallel plates. As it moves toward the negative plate, which of the following statements is true about its energy?

Accepted Answer

Its kinetic energy increases and its potential energy decreases.

Question 2

Which equation correctly expresses the work done by a constant force $$\vec{F}$$ over a displacement $$\Delta \vec{r} at an $$angle $$	heta$$?

Accepted Answer

$$W = F \Delta r \cos 	heta$$

Question 3

The electric potential energy $$U of $$two point charges $$q_1$$ and $$q_2$$ separated by a distance $$r is $$given by:

Accepted Answer

$$U = k \dfrac{q_1$ q_2$}{r}$$

Question 4

A negative charge moves in the direction of a uniform electric field. What happens to its kinetic and potential energy?

Accepted Answer

Kinetic energy decreases, potential energy increases (becomes less negative).

Question 5

Which of the following best describes why the electric force is considered conservative?

Accepted Answer

The work done by the electric force depends only on the initial and final positions.

Question 6

What is the electric potential $$V at a $$distance $$r$$ from a point charge $$q$$?

Accepted Answer

$$V = k \dfrac{q}{r}$$

Question 7

A 1-coulomb charge is moved through a potential difference of 1 volt. How much work is done?

Accepted Answer

$$1~	ext{J}$$

Question 8

If a positive charge moves opposite to the direction of a uniform electric field, what happens to its speed and potential energy?

Accepted Answer

It slows down and its potential energy increases.

Question 9

The electric potential difference $$\Delta V$$ between two points $$A$$ and $$B in a $$uniform electric field $$E$$ separated by distance $$d is$$:

Accepted Answer

$$\Delta V = -Ed$$

Question 10

Which of the following is true about the total mechanical energy of a charged particle in a uniform electric field (neglecting non-conservative forces)?

Accepted Answer

It remains constant.

Question 11

A system consists of three point charges: $$q_1$$, $$q_2$$, and $$q_3. $$What is the total electrostatic potential energy of the system?

Accepted Answer

$$U = k \left( \dfrac{q_1$ q_2$}{r_{12}} + \dfrac{q_1$ q_3$}{r_{13}} + \dfrac{q_2$ q_3$}{r_{23}} \right)$$

Question 12

Which of the following is the correct relationship between electric field $$E$$ and electric potential $$V in a $$region where $$E is $$constant?

Accepted Answer

$$E = -\dfrac{dV}{dx}$$

Question 13

A ring of radius $$R$$ carries a total charge $$Q$$ uniformly distributed. What is the electric potential at the center of the ring?

Accepted Answer

$$V = k \dfrac{Q}{R}$$

Question 14

Which of the following statements about electric potential is correct?

Accepted Answer

Electric potential is a scalar quantity.

Question 15

A positive charge is moved from point A to point B in an electric field, and the potential at B is lower than at A. What can be said about the work done by the field?

Accepted Answer

The field does positive work.

Question 16

The electron-volt (eV) is a unit of energy commonly used in atomic physics. How much energy in joules is 1 eV?

Accepted Answer

$$1.6 	imes 10$$^{-19}$$~	ext{J}$$

Question 17

If two like charges are brought closer together, what happens to the system's electric potential energy?

Accepted Answer

It increases.

Question 18

Which of the following is true about the potential difference between two points in a uniform electric field?

Accepted Answer

It depends only on the magnitude of the field and the distance between the points.

Question 19

A semicircular ring of radius $$R$$ carries a total charge $$Q$$ uniformly distributed. What is the electric potential at the center of the semicircle?

Accepted Answer

$$V = k \dfrac{2Q}{\pi R}$$

Question 20

A charge $$q is $$moved from infinity to a distance $$r$$ from a point charge $$Q. $$What is the change in electric potential energy?

Accepted Answer

$$\Delta U = k \dfrac{qQ}{r}$$

Electric Potential and Electric Potential Energy (Chapter 25) – Study Notes

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