Q: A uniform electric field of magnitude $$E = 35,000 \ \mathrm{N/C}$$ makes an angle of $$47^\circ$$ with a plane surface of area $$A = 0.0153 \ \mathrm{m}^2. $$What is the electric flux through the surface?

$$\Phi = EA \cos \theta = 35,000 \times 0.0153 \times \cos 47^\circ = 364 \ \mathrm{N} \cdot \mathrm{m}^2/\mathrm{C}$$

Q: A proton is released from rest in a uniform electric field of $$2.18 \times 10^5$ \ \mathrm{N/C}. $$What is the acceleration of the proton? ($$m_p = 1.673 \times 10$$^{-27}$$ \ \mathrm{kg}$$, $$q = 1.60 \times 10$$^{-19}$$ \ \mathrm{C})$$

$$a = \dfrac{qE}{m_p} = \dfrac{1.60 \times 10$$^{-19}$$ \times 2.18 \times 10^5$}{1.673 \times 10$$^{-27}$$} = 2.08 \times 10$$^{13}$$ \ \mathrm{m/s}^2$$

Question 1

Which of the following statements best describes the conservation of electric charge?

Accepted Answer

The total electric charge of the universe is a constant; charge is conserved in all processes.

Question 2

A glass rod is rubbed with silk and becomes positively charged. What happens at the atomic level?

Accepted Answer

Electrons are transferred from the glass rod to the silk.

Question 3

Which of the following materials is most likely to be a good conductor of electricity?

Accepted Answer

Copper

Question 4

What is the magnitude of the force between two point charges, $$q_1 = 2.0$$ \ \mu\mathrm{C}$$ and q_2$ = -3.0 \ \mu\mathrm{C}$$, separated by $$0.50 \ \mathrm{m} in $$air? Use $$k = 8.99 	imes 10^9$ \ \mathrm{N} \cdot \mathrm{m}^2 / \mathrm{C}^2.$$

Accepted Answer

$$F = 0.216 \ \mathrm{N}$$

Question 5

A point charge $$q$$ creates an electric field at a distance $$r$$ given by which of the following equations?

Accepted Answer

$$E = \dfrac{kq}{r^2$}$$

Question 6

A neutral object is attracted to a charged rod. Which phenomenon best explains this attraction?

Accepted Answer

The neutral object becomes polarized, with its charges rearranged by the external field.

Question 7

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

Accepted Answer

Electric field lines can cross each other.

Question 8

A parallel-plate capacitor has plates of area $$A$$ and separation $$d$$, with charges $$+Q$$ and $$-Q. $$What is the direction of the electric field between the plates?

Accepted Answer

From the positive plate to the negative plate

Question 9

A conductor is placed in an external electric field and reaches electrostatic equilibrium. Which statement is correct?

Accepted Answer

The electric field inside the conductor is zero.

Question 10

A spherical conductor is given a net positive charge. Where does the excess charge reside?

Accepted Answer

On the outer surface only

Question 11

Which of the following best describes the process of charging a conductor by induction?

Accepted Answer

Bringing a charged object near the conductor, grounding the conductor, then removing the ground before the charged object

Question 12

A uniform electric field of magnitude $$E = 35,000 \ \mathrm{N/C}$$ makes an angle of $$47^\circ$$ with a plane surface of area $$A = 0.0153 \ \mathrm{m}^2. $$What is the electric flux through the surface?

Accepted Answer

$$\Phi = EA \cos 	heta = 35,000 	imes 0.0153 	imes \cos 47^\circ = 364 \ \mathrm{N} \cdot \mathrm{m}^2/\mathrm{C}$$

Question 13

According to Gauss’s Law, what is the electric flux through a closed surface enclosing a net charge $$q$$?

Accepted Answer

$$\Phi = \dfrac{q}{\$$varepsilon_0$$}$$

Question 14

A proton is released from rest in a uniform electric field of $$2.18 	imes 10^5$ \ \mathrm{N/C}. $$What is the acceleration of the proton? ($$m_p = 1.673 	imes 10$$^{-27}$$ \ \mathrm{kg}$$, $$q = 1.60 	imes 10$$^{-19}$$ \ \mathrm{C})$$

Accepted Answer

$$a = \dfrac{qE}{m_p} = \dfrac{1.60 	imes 10$$^{-19}$$ 	imes 2.18 	imes 10^5$}{1.673 	imes 10$$^{-27}$$} = 2.08 	imes 10$$^{13}$$ \ \mathrm{m/s}^2$$

Question 15

Which of the following is TRUE about the electric field at the surface of a conductor in electrostatic equilibrium?

Accepted Answer

The electric field is perpendicular to the surface.

Question 16

A surface encloses three charges: $$q_1 = 3.2$$ \ \mu\mathrm{C}$$, q_2$ = 6.9 \ \mu\mathrm{C}$$, and $$q_3 = -4.1$$ \ \mu\mathrm{C}$$. What is the total electric flux through the surface?

Accepted Answer

$$\Phi = \dfrac{q_1$ + q_2$ + q_3$}{\$$varepsilon_0$$} = \dfrac{3.2 + 6.9 - 4.1}{8.85 	imes 10$$^{-12}$$} = 6.0 	imes 10^5$ \ \mathrm{N} \cdot \mathrm{m}^2/\mathrm{C}$$

Question 17

Which of the following best explains why lightning rods are pointed?

Accepted Answer

The electric field is stronger at sharp points, concentrating charge and encouraging discharge.

Question 18

A photoconductive material is exposed to light. What happens to its electrical properties?

Accepted Answer

It becomes a better conductor.

Question 19

Which of the following is a correct statement of Coulomb’s Law for the force between two point charges?

Accepted Answer

$$F = k \dfrac{|q_1$ q_2$|}{r^2$}$$

Chapter 19: Electric Charges, Forces, and Fields – Study Notes

Guida di studio - Domande di pratica

Study guide - Flashcard