Question 1

A thin, uniformly charged rod of length $$L$$ carries a total charge $$Q. $$What is the magnitude of the electric field at a point $$P$$ located a distance $$a$$ from one end of the rod along the line extending from the rod (not perpendicular to it)?

Accepted Answer

$$E = \frac{1}{4\pi\$$epsilon_0$$} \frac{Q}{a(a+L)}$$

Question 2

Two point charges, $$q_1 = +2$$\ \mu\mathrm{C}$$ and q_2$ = -2\ \mu\mathrm{C}$$, are placed 10 cm apart. What is the net electric field at the midpoint between them?

Accepted Answer

$$E = \frac{1}{4\pi\$$epsilon_0$$} \frac{4q}{(0.05)^2$}$$

Question 3

A solid non-conducting sphere of radius $$R$$ has a uniform charge density $$\rho. $$Using Gauss' Law, what is the electric field at a distance $$r \u003c R$$ from the center?

Accepted Answer

$$E = \frac{\rho r}{3\$$epsilon_0$$}$$

Question 4

Which of the following statements about electric potential energy is correct?

Accepted Answer

It can be positive or negative depending on the configuration of charges.

Question 5

A proton is released from rest at a point where the electric potential is $$V_0. $$What is its kinetic energy after moving to a point where the potential is zero?

Accepted Answer

$$KE = eV_0$

Question 6

Which of the following best describes the relationship between electric field $$\vec{E}$$ and electric potential $$V$$?

Accepted Answer

$$\vec{E} = -
abla V$$

Question 7

A group of three point charges, $$q_1$$, $$q_2$$, and $$q_3$$, are assembled from infinity to form a triangle. Which expression gives the total electrostatic potential energy of the system?

Accepted Answer

$$U = \frac{1}{4\pi\$$epsilon_0$$} \left( \frac{q_1$ q_2$}{r_{12}} + \frac{q_1$ q_3$}{r_{13}} + \frac{q_2$ q_3$}{r_{23}} \right)$$

Question 8

A charge $$q is $$moved from point $$A to $$point $$B in an $$electric field. The potential at $$A is$$ $$V_A$$ and at $$B is$$ $$V_B. $$What is the work done by the electric field?

Accepted Answer

$$W = q(V_A - V_B)$$

Question 9

A spherical shell of radius $$R$$ carries a uniform surface charge density $$\sigma. $$What is the electric field at a point outside the shell at distance $$r \u003e R$$?

Accepted Answer

$$E = \frac{1}{4\pi\$$epsilon_0$$} \frac{Q}{r^2$}$$

Question 10

Which of the following is a correct application of Gauss' Law?

Accepted Answer

The net electric flux through a closed surface is proportional to the net charge enclosed.

Question 11

A negative charge is released from rest in a region of increasing electric potential. What happens to its kinetic energy?

Accepted Answer

It increases.

Question 12

A point charge $$q is $$placed at the center of a cube. What is the total electric flux through all six faces of the cube?

Accepted Answer

$$\Phi_E = \frac{q}{\$$epsilon_0$$}$$

Question 13

Which of the following best describes the gradient operator $$
abla in $$the context of electric potential?

Accepted Answer

It gives the direction and rate of the steepest increase of the potential.

Question 14

A charge $$q is $$placed in a uniform electric field $$\vec{E}. $$What is the potential difference between two points separated by a distance $$d$$ along the direction of the field?

Accepted Answer

$$\Delta V = -Ed$$

Question 15

A spacecraft must escape Earth's electric field. If the Earth's net charge is $$Q$$ and the spacecraft has charge $$q$$, what is the minimum work required to move the spacecraft from the Earth's surface (radius $$R) to $$infinity?

Accepted Answer

$$W = \frac{1}{4\pi\$$epsilon_0$$} \frac{Qq}{R}$$

Question 16

Which of the following is true about the electric field inside a conductor in electrostatic equilibrium?

Accepted Answer

The electric field is zero everywhere inside the conductor.

Question 17

A charge $$q is $$moved in a circle of radius $$r$$ around a point charge $$Q. $$What is the work done by the electric field?

Accepted Answer

$$W = 0$$

Exam 01 Review: Electrostatics and Electric Potential (PHYS 2200)

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