Q: A solid conducting sphere of radius $$0.100\ \mathrm{m}$$ bears a net charge $$Q_{\mathrm{in}} = 4.50 \times 10$$^{-6}$$\ \mathrm{C}. $$What is the electric field strength at a point $$0.250\ \mathrm{m}$$ from the center of the sphere?

$$7.19 \times 10^4$\ \mathrm{N/C}$$

Q: Two spheres of equal mass $$m$$, each carrying a charge $$+Q$$, are suspended from a string of length $$L$$ and allowed to come to equilibrium. What is the equilibrium angle $$\theta$$ between the strings if the spheres are separated by a distance $$x$$?

$$\theta = \sqrt{\frac{Q^2$}{16\pi\$$epsilon_0$$ mL}}$$

Q: If a solid conducting sphere of radius $$0.100\ \mathrm{m}$$ bears a net charge $$Q_{\mathrm{in}} = 4.50 \times 10$$^{-6}$$\ \mathrm{C}$$, what is the electric field strength at a point $$0.0500\ \mathrm{m}$$ from the center of the sphere?

$$5.58 \times 10^5$\ \mathrm{N/C}$$

Q: What is the surface charge density on the outer surface of the middle conductor (spherical shell) of radius $$0.500\ \mathrm{m} if it $$has a net charge $$Q_{\mathrm{out}} = -7.50 \times 10$$^{-6}$$\ \mathrm{C}$$?

$$-2.39 \times 10$$^{-5}$$\ \mathrm{C/m}^2$$

Q: A solid conducting sphere of radius $$0.100\ \mathrm{m}$$ bears a net charge $$Q_{\mathrm{in}} = 4.50 \times 10$$^{-6}$$\ \mathrm{C}. A $$concentric conducting spherical shell has an inner radius of $$0.400\ \mathrm{m}$$ and an outer radius of $$0.500\ \mathrm{m}$$, with a net charge $$Q_{\mathrm{out}} = -7.50 \times 10$$^{-6}$$\ \mathrm{C}. $$What is the electric field strength at a point $$0.420\ \mathrm{m}$$ from the center?

$$8.58 \times 10^4$\ \mathrm{N/C}$$

Question 1

Which SI prefix corresponds to a factor of $$10^{12}$$?

Accepted Answer

tera

Question 2

A solid conducting sphere of radius $$0.100\ \mathrm{m}$$ bears a net charge $$Q_{\mathrm{in}} = 4.50 	imes 10$$^{-6}$$\ \mathrm{C}. $$What is the electric field strength at a point $$0.250\ \mathrm{m}$$ from the center of the sphere?

Accepted Answer

$$7.19 	imes 10^4$\ \mathrm{N/C}$$

Question 3

Two identical parallel plate capacitors, each with capacitance $$C$$, are joined together to form a single capacitor as shown in Figure 14-2. What is the final capacitance?

Accepted Answer

$$\frac{C}{2}$$

Question 4

A spherical balloon contains a positive charge at its center. As the balloon is inflated to a greater volume while the charge remains at the center, how does the electric flux through the surface of the balloon change?

Accepted Answer

The flux remains the same and field strength decreases.

Question 5

What is the electric potential energy of a system consisting of charges $$q_1 = -2.00$$\ \mu\mathrm{C}$$, q_2$ = +3.00\ \mu\mathrm{C}$$, and $$q_3 = +1.50$$\ \mu\mathrm{C}$$, each separated by d = 15.0$$\ \mathrm{cm}$$ on the x-axis?

Accepted Answer

$$0.305\ \mathrm{J}$$

Question 6

A student has three copper wires of different lengths and cross-sectional areas. Wire A has length $$l$$ and diameter $$D$$, wire B has length $$2l$$ and diameter $$2D$$, and wire C has length $$l$$ and diameter $$D/2. $$Rank in order, from largest to smallest, the resistances $$R_A$$, $$R_B$$, and $$R_C.$$

Accepted Answer

$$R_C \u003e R_A \u003e R_B$$

Question 7

The total net flux of the electric field through the six faces of a certain cube is $$+\$$Phi_0$$, where $$\$$Phi_0 is a $$positive constant. Which of the following statements is necessarily true?

Accepted Answer

More electric field lines exit the cube than enter the cube.

Question 8

Consider a circuit with a $$9\ \mathrm{V}$$ battery and two capacitors, $$C_1 = 5.0$$\ \mu\mathrm{F}$$ and C_2$ = 4.0\ \mu\mathrm{F}$$, connected in series. What is the charge on the $$5.0\ \mu\mathrm{F}$$ capacitor?

Accepted Answer

$$20.0\ \mu\mathrm{C}$$

Question 9

Two spheres of equal mass $$m$$, each carrying a charge $$+Q$$, are suspended from a string of length $$L$$ and allowed to come to equilibrium. What is the equilibrium angle $$	heta$$ between the strings if the spheres are separated by a distance $$x$$?

Accepted Answer

$$	heta = \sqrt{\frac{Q^2$}{16\pi\$$epsilon_0$$ mL}}$$

Question 10

A piece of copper wire joins a piece of aluminum wire whose radius is twice that of the copper. Current $$I$$ flows through the copper wire. The conduction electron density in copper is $$8.5 	imes 10$$^{28}$$\ \mathrm{m}^{-3}$$, and in aluminum it is $$6.02 	imes 10$$^{28}$$\ \mathrm{m}^{-3}. $$What is the ratio of the electron drift speed in the copper wire to the electron drift speed in the aluminum wire?

Accepted Answer

2.24

Question 11

What is the sign of the electric flux through the right end-cap of a cylinder if positive and negative charges of equal magnitude lie along the symmetry axis at a distance $$L$$ from each end-cap?

Accepted Answer

negative

Question 12

If a solid conducting sphere of radius $$0.100\ \mathrm{m}$$ bears a net charge $$Q_{\mathrm{in}} = 4.50 	imes 10$$^{-6}$$\ \mathrm{C}$$, what is the electric field strength at a point $$0.0500\ \mathrm{m}$$ from the center of the sphere?

Accepted Answer

$$5.58 	imes 10^5$\ \mathrm{N/C}$$

Question 13

What is the surface charge density on the outer surface of the middle conductor (spherical shell) of radius $$0.500\ \mathrm{m} if it $$has a net charge $$Q_{\mathrm{out}} = -7.50 	imes 10$$^{-6}$$\ \mathrm{C}$$?

Accepted Answer

$$-2.39 	imes 10$$^{-5}$$\ \mathrm{C/m}^2$$

Question 14

Rank order from largest to smallest the electric field strengths at points A through D identified in the contour diagram, where point D is closest to the positive plate and point A is closest to the negative plate.

Accepted Answer

$$E_D \u003e E_B \u003e E_C \u003e E_A$$

Question 15

What is the direction of the electric field at point C in the contour diagram, where the positive plate is at the top and the negative plate is at the bottom?

Accepted Answer

down toward the bottom of the page

Question 16

Two spherical conductors are separated by a large distance. They each carry the same positive charge $$Q. $$Conductor A has a larger radius than conductor B. Compare the electric potential at the surface of conductor A with the electric potential at the surface of conductor B.

Accepted Answer

$$V_A \u003c V_B$$

Question 17

The two conductors are now connected by a wire. What happens to the charge on conductor A after it is connected to conductor B?

Accepted Answer

The charge on conductor A decreases.

Question 18

A solid conducting sphere of radius $$0.100\ \mathrm{m}$$ bears a net charge $$Q_{\mathrm{in}} = 4.50 	imes 10$$^{-6}$$\ \mathrm{C}. A $$concentric conducting spherical shell has an inner radius of $$0.400\ \mathrm{m}$$ and an outer radius of $$0.500\ \mathrm{m}$$, with a net charge $$Q_{\mathrm{out}} = -7.50 	imes 10$$^{-6}$$\ \mathrm{C}. $$What is the electric field strength at a point $$0.420\ \mathrm{m}$$ from the center?

Accepted Answer

$$8.58 	imes 10^4$\ \mathrm{N/C}$$

Physics Exam Study Guide: Electric Fields, Flux, Capacitance, and Current

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