Q: A point charge of $$5.00\ \mathrm{mC} is $$placed at the origin. What is the magnitude of the electric field $$1.00\ \mathrm{m}$$ away from the charge?

$$4.49 \times 10^7$\ \mathrm{N/C}$$

Question 1

Which of the following statements best describes why lightning rods are pointed at the top?

Accepted Answer

The sharp tip increases the local electric field, making it more likely to ionize air and safely discharge electricity.

Question 2

A neutral object becomes positively charged after being rubbed with a cloth. What has happened at the atomic level?

Accepted Answer

Electrons have been removed from the object, leaving an excess of protons.

Question 3

How many electrons must be removed from a neutral object to leave a net charge of $$0.500\ \mu\mathrm{C}$$?

Accepted Answer

$$3.13 	imes 10$$^{12}$$

Question 4

Which of the following best explains why a child’s hair stands on end after going down a plastic slide?

Accepted Answer

Friction transfers electrons, causing each hair to acquire the same charge and repel each other.

Question 5

Which equation correctly expresses Coulomb’s Law for the force between two point charges?

Accepted Answer

$$F = k \frac{Q_1$ Q_2$}{r^2$}$$

Question 6

A point charge of $$5.00\ \mathrm{mC} is $$placed at the origin. What is the magnitude of the electric field $$1.00\ \mathrm{m}$$ away from the charge?

Accepted Answer

$$4.49 	imes 10^7$\ \mathrm{N/C}$$

Question 7

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

Accepted Answer

The electric field inside the conductor is zero.

Question 8

A negative test charge is placed in an electric field. In which direction does the force on the charge act?

Accepted Answer

Opposite to the direction of the electric field.

Question 9

Which of the following best describes the principle of superposition as it applies to electric fields?

Accepted Answer

The net electric field is the vector sum of the electric fields produced by each charge.

Question 10

A Faraday cage shields its interior from external electric fields because:

Accepted Answer

The electric field inside a conductor is zero, so the cage redistributes charges to cancel external fields.

Question 11

Which of the following is the correct expression for electric flux through a surface?

Accepted Answer

$$\Phi_E = E A \cos 	heta$$

Question 12

According to Gauss’s Law, the net electric flux through a closed surface is proportional to:

Accepted Answer

The net charge enclosed within the surface.

Question 13

A bacteria has $$3.3 	imes 10$$^{11}$$ protons and a net charge of 0.300$$\ \mathrm{pC}$$. Are there more protons or electrons?

Accepted Answer

More protons (total/net charge is positive)

Question 14

Which of the following is NOT a property of electric field lines?

Accepted Answer

They can cross each other.

Question 15

A $$-2\ \mu\mathrm{C}$$ charge experiences an upward force of $$2.0 	imes 10$$^{-4}$$\ \mathrm{N}. $$What is the magnitude and direction of the electric field?

Accepted Answer

$$100\ \mathrm{N/C}$$ and downward

Question 16

Which of the following best describes the difference between conductors and insulators?

Accepted Answer

Conductors allow charge to flow freely; insulators do not.

Question 17

If two identical conducting spheres, one charged and one neutral, are touched together and then separated, what happens to the charge?

Accepted Answer

The charge is shared equally between the two spheres.

Question 18

Which of the following is the correct value for the permittivity of free space $$\$$epsilon_0$$?

Accepted Answer

$$8.85 	imes 10$$^{-12}$$\ \mathrm{C}^2/\mathrm{N} \cdot \mathrm{m}^2$$

Question 19

Which of the following is a real-world application of electrostatics?

Accepted Answer

Laser printers use electrostatic charges to control toner placement on paper.

Chapter 16: Electric Charge and Electric Field – Physics with Calculus Study Notes

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