Q: A proton (charge $$q = +e) is $$placed in a uniform electric field of magnitude $$E = 2.0 \times 10^4$\ \mathrm{N/C}$$ directed to the right. What is the magnitude and direction of the force on the proton?

$$F = 3.2 \times 10$$^{-15}$$\ \mathrm{N}$$, to the right

Question 1

A proton (charge $$q = +e) is $$placed in a uniform electric field of magnitude $$E = 2.0 	imes 10^4$\ \mathrm{N/C}$$ directed to the right. What is the magnitude and direction of the force on the proton?

Accepted Answer

$$F = 3.2 	imes 10$$^{-15}$$\ \mathrm{N}$$, to the right

Question 2

Which of the following statements about electric field lines is correct?

Accepted Answer

Electric field lines begin on positive charges and end on negative charges.

Question 3

A small negative charge is placed near a large, isolated, positively charged conducting sphere. What is the direction of the electric field at a point just outside the surface of the sphere?

Accepted Answer

Radially outward from the center of the sphere

Question 4

A thin, infinite sheet has a uniform surface charge density $$\sigma = 5.0 	imes 10$$^{-6}$$\ \mathrm{C/m^2$}. $$What is the magnitude of the electric field produced by the sheet?

Accepted Answer

$$E = \dfrac{\sigma}{2\$$epsilon_0$$}$$

Question 5

Which of the following best describes the electric field inside a uniformly charged conducting sphere?

Accepted Answer

It is zero everywhere inside the sphere.

Question 6

A point charge $$q is $$located at the center of a spherical Gaussian surface of radius $$r. $$What is the net electric flux through the surface?

Accepted Answer

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

Question 7

A dipole with dipole moment $$\vec{p} is $$placed in a uniform electric field $$\vec{E}. $$Which expression gives the potential energy of the dipole in the field?

Accepted Answer

$$U = -\vec{p} \cdot \vec{E}$$

Question 8

Two point charges, $$q_1 = +2.0$$ 	imes $$10^{-6}$$\ \mathrm{C}$$ and q_2$ = -3.0 	imes 10$$^{-6}$$\ \mathrm{C}$$, are separated by $$0.10\ \mathrm{m}. $$What is the magnitude of the force between them?

Accepted Answer

$$F = 540\ \mathrm{N}$$

Question 9

A long, straight wire has a uniform linear charge density $$\lambda. At a $$distance $$r$$ from the wire, what is the magnitude of the electric field?

Accepted Answer

$$E = \dfrac{\lambda}{2\pi\$$epsilon_0$$ r}$$

Question 10

A parallel-plate capacitor consists of two large plates, each with area $$A$$, separated by a small distance $$d. $$The plates carry equal and opposite charges $$\pm Q. $$What is the magnitude of the electric field between the plates (neglecting edge effects)?

Accepted Answer

$$E = \dfrac{Q}{A\$$epsilon_0$$}$$

Question 11

A uniformly charged insulating sphere of radius $$R$$ and total charge $$Q$$ has an electric field at a distance $$r \u003c R$$ from its center given by:

Accepted Answer

$$E = \dfrac{1}{4\pi\$$epsilon_0$$} \dfrac{Q}{R^3$} r$$

Question 12

A charged particle of mass $$m$$ and charge $$q is $$released from rest in a uniform electric field $$\vec{E}. $$What is its acceleration?

Accepted Answer

$$a = \dfrac{q}{m} E$$

Question 13

Which of the following is true about the net charge on an isolated conductor?

Accepted Answer

It resides entirely on the outer surface.

Question 14

A small test charge $$q_0 is $$placed at a distance $$r$$ from a point charge $$Q. $$What is the electric field at that point?

Accepted Answer

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

Question 15

A closed surface encloses a net charge of $$-2.0 	imes 10$$^{-6}$$\ \mathrm{C}. $$What is the net electric flux through the surface?

Accepted Answer

$$\Phi_E = -2.3 	imes 10^5$\ \mathrm{N\cdot m^2$/C}$$

Question 16

A dipole is placed in a uniform electric field. Which of the following statements is correct?

Accepted Answer

The net force on the dipole is zero, but it experiences a torque.

Question 17

A metal sphere is given a net negative charge and is isolated in space. What is the direction of the electric field just outside its surface?

Accepted Answer

Radially inward toward the center

Question 18

A continuous charge distribution has a volume charge density $$\rho. $$What is the infinitesimal charge $$dq in a $$small volume element $$dV$$?

Accepted Answer

$$dq = \rho dV$$

Question 19

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

Accepted Answer

The net electric flux through a closed surface depends only on the net charge enclosed.

Electric Charge, Electric Field, and Gauss's Law: Exam 1 Review Notes

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