Q: A sphere of radius $$0.05\ \text{m}$$ has a uniform surface charge density $$\sigma = 2.0 \times 10$$^{-6}$$\ \text{C}/\text{m}^2. $$What is the total charge on the sphere?

$$Q = 1.57 \times 10$$^{-7}$$\ \text{C}$$

Q: A point charge $$q = +5.0 \times 10$$^{-6}$$\ \text{C} is $$placed at the origin. What is the electric field at a point $$0.20\ \text{m}$$ away from the charge? (Use $$k = 8.99 \times 10^9$\ \text{N}\cdot\text{m}^2/\text{C}^2)$$

$$E = 1.12 \times 10^6$\ \text{N/C}$$

Q: A $$+3.0\ \text{MC}$$ charge is placed in a uniform electric field of $$2.0 \times 10^4$\ \text{N/C}$$ directed to the right. What is the force on the charge?

$$F = 6.0 \times 10^4$\ \text{N}$$

Q: A proton ($$m_p = 1.67 \times 10$$^{-27}$$\ \text{kg}$$, $$q = +1.60 \times 10$$^{-19}$$\ \text{C}) is $$accelerated from rest through a potential difference of $$1,000\ \text{V}. $$What is its final speed?

$$v = 1.39 \times 10^5$\ \text{m/s}$$

Q: A uniform electric field of $$E = 4.0 \times 10^3$\ \text{N/C}$$ makes an angle of $$30^\circ$$ with a surface of area $$A = 0.02\ \text{m}^2. $$What is the electric flux through the surface?

$$\Phi = 69.3\ \text{N}\cdot\text{m}^2/\text{C}$$

Q: A $$+2.0\ \text{MC}$$ charge is moved $$0.10\ \text{m} in $$the direction of a uniform electric field $$E = 1.5 \times 10^4$\ \text{N/C}. $$What is the change in electric potential energy?

$$\Delta U = -3.0 \times 10^2$\ \text{J}$$

Question 1

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

Accepted Answer

The total charge in a closed system remains constant; charge is only transferred, not created or destroyed.

Question 2

A glass rod is rubbed with silk, resulting in the glass rod becoming positively charged. Which process is responsible for this phenomenon?

Accepted Answer

Charging by friction

Question 3

What is the magnitude of the electric force between two point charges, $$q_1 = +2.0$$ 	imes $$10^{-6}$$\ 	ext{C}$$ and q_2$ = -3.0 	imes 10$$^{-6}$$\ 	ext{C}$$, separated by $$0.15\ 	ext{m} in $$air? (Use $$k = 8.99 	imes 10^9$\ 	ext{N}\cdot	ext{m}^2/	ext{C}^2)$$

Accepted Answer

$$F = 2.40\ 	ext{N}$$

Question 4

Which of the following best explains why a charged balloon can stick to a neutral wall?

Accepted Answer

The wall is polarized; its charges rearrange so that opposite charges are closer to the balloon.

Question 5

A sphere of radius $$0.05\ 	ext{m}$$ has a uniform surface charge density $$\sigma = 2.0 	imes 10$$^{-6}$$\ 	ext{C}/	ext{m}^2. $$What is the total charge on the sphere?

Accepted Answer

$$Q = 1.57 	imes 10$$^{-7}$$\ 	ext{C}$$

Question 6

Which of the following is true about conductors at electrostatic equilibrium?

Accepted Answer

The electric field inside the conductor is zero.

Question 7

A point charge $$q = +5.0 	imes 10$$^{-6}$$\ 	ext{C} is $$placed at the origin. What is the electric field at a point $$0.20\ 	ext{m}$$ away from the charge? (Use $$k = 8.99 	imes 10^9$\ 	ext{N}\cdot	ext{m}^2/	ext{C}^2)$$

Accepted Answer

$$E = 1.12 	imes 10^6$\ 	ext{N/C}$$

Question 8

Which experiment confirmed that electric charge is quantized?

Accepted Answer

Millikan's oil drop experiment

Question 9

A parallel-plate capacitor has plates separated by $$d = 0.002\ 	ext{m}$$ and a potential difference $$V = 100\ 	ext{V}. $$What is the magnitude of the electric field between the plates?

Accepted Answer

$$E = 5,000\ 	ext{N/C}$$

Question 10

A $$+3.0\ 	ext{MC}$$ charge is placed in a uniform electric field of $$2.0 	imes 10^4$\ 	ext{N/C}$$ directed to the right. What is the force on the charge?

Accepted Answer

$$F = 6.0 	imes 10^4$\ 	ext{N}$$

Question 11

A proton ($$m_p = 1.67 	imes 10$$^{-27}$$\ 	ext{kg}$$, $$q = +1.60 	imes 10$$^{-19}$$\ 	ext{C}) is $$accelerated from rest through a potential difference of $$1,000\ 	ext{V}. $$What is its final speed?

Accepted Answer

$$v = 1.39 	imes 10^5$\ 	ext{m/s}$$

Question 12

Which of the following is NOT a property of electric charge?

Accepted Answer

Charge can be destroyed in ordinary physical processes.

Question 13

A uniform electric field of $$E = 4.0 	imes 10^3$\ 	ext{N/C}$$ makes an angle of $$30^\circ$$ with a surface of area $$A = 0.02\ 	ext{m}^2. $$What is the electric flux through the surface?

Accepted Answer

$$\Phi = 69.3\ 	ext{N}\cdot	ext{m}^2/	ext{C}$$

Question 14

A $$+2.0\ 	ext{MC}$$ charge is moved $$0.10\ 	ext{m} in $$the direction of a uniform electric field $$E = 1.5 	imes 10^4$\ 	ext{N/C}. $$What is the change in electric potential energy?

Accepted Answer

$$\Delta U = -3.0 	imes 10^2$\ 	ext{J}$$

Question 15

Which of the following best describes the behavior of excess charge in a conductor?

Accepted Answer

Excess charge moves to the surface of the conductor.

Question 16

A capacitor with plate area $$A = 0.01\ 	ext{m}^2$$ and separation $$d = 0.002\ 	ext{m} is $$filled with a dielectric of $$\kappa = 5. $$What is its capacitance? ($$\$$varepsilon_0$$ = 8.85 	imes 10$$^{-12}$$\ 	ext{F/m})$$

Accepted Answer

$$C = 2.21 	imes 10$$^{-10}$$\ 	ext{F}$$

Question 17

A charge $$q = +1.0 	imes 10$$^{-6}$$\ 	ext{C} is $$placed at the center of a spherical surface of radius $$0.10\ 	ext{m}. $$What is the electric flux through the surface?

Accepted Answer

$$\Phi = 1.13 	imes 10^4$\ 	ext{N}\cdot	ext{m}^2/	ext{C}$$

Question 18

A $$+4.0\ 	ext{MC}$$ charge is moved from point A to point B in a uniform electric field of $$E = 2.0 	imes 10^4$\ 	ext{N/C}$$ over a distance $$d = 0.05\ 	ext{m}$$, parallel to the field. What is the work done by the electric field?

Accepted Answer

$$W = 4.0 	imes 10^3$\ 	ext{J}$$

Electric Charge, Electric Fields, Gauss's Law, and Electric Potential

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