Question 1

A plastic rod is rubbed with wool and then brought near a thin stream of water, causing the water to bend toward the rod. Which of the following best explains this phenomenon?

Accepted Answer

The rod becomes negatively charged and polarizes the water molecules, resulting in an attractive force.

Question 2

Which of the following statements about conductors and insulators is correct?

Accepted Answer

Charge can move freely through conductors but not through insulators.

Question 3

A glass rod rubbed with silk acquires a positive charge. What happens to the silk?

Accepted Answer

It acquires a negative charge equal in magnitude to the rod.

Question 4

Which equation correctly expresses Coulomb’s law for the magnitude of the force between two point charges $$q_1$$ and $$q_2$$ separated by a distance $$r$$?

Accepted Answer

$$F = K \frac{q_1$ q_2$}{r^2$}$$

Question 5

A neutral metal sphere is brought near a negatively charged rod. What happens to the charges in the sphere?

Accepted Answer

Positive charges in the sphere move toward the rod, and negative charges move away.

Question 6

A parallel-plate capacitor has a uniform electric field between its plates. Which equation gives the electric field $$E in $$terms of the charge $$Q on $$the plates and the area $$A$$?

Accepted Answer

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

Question 7

Which of the following best describes the electric field inside a conductor in electrostatic equilibrium?

Accepted Answer

It is zero everywhere inside the conductor.

Question 8

A small bead with charge $$+10 nC is $$placed at the origin. What is the magnitude of the electric field at the point $$(3.0\ 	ext{cm}, 4.0\ 	ext{cm})$$?

Accepted Answer

$$E = \frac{Kq}{r^2$}$$, where $$r = 0.05 m$$

Question 9

Which of the following changes would increase the electric field strength between two parallel plates of a capacitor?

Accepted Answer

Increasing the magnitude of the charge on both plates.

Question 10

A DNA fragment with negative charge is placed in a gel electrophoresis apparatus with a uniform electric field. What is the direction of the force on the DNA fragment?

Accepted Answer

Toward the positive electrode.

Question 11

A dipole is placed in a uniform electric field. What happens to the dipole?

Accepted Answer

It experiences a net torque and rotates to align with the field.

Question 12

Which of the following is true about the law of conservation of charge?

Accepted Answer

Charge is neither created nor destroyed, only transferred.

Question 13

A proton and an electron are placed in the same uniform electric field. How do their accelerations compare?

Accepted Answer

The electron has a larger acceleration.

Question 14

Which of the following best describes the direction of electric field lines?

Accepted Answer

They start on positive charges and end on negative charges.

Question 15

If the distance between two point charges is halved, what happens to the magnitude of the force between them according to Coulomb’s law?

Accepted Answer

It becomes four times as large.

Question 16

A negatively charged rod is brought near a neutral metal sphere. What type of force acts between them?

Accepted Answer

An attractive force.

Question 17

Which of the following is a real-world application of the electric field concept discussed in the chapter?

Accepted Answer

The use of electric fields in air cleaners to remove dust and soot.

Chapter 20: Electric Fields and Forces – Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards