Question 1

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

Accepted Answer

Electric charge can neither be created nor destroyed; it can only be transferred from one object to another.

Question 2

A glass rod is rubbed with silk, resulting in the rod becoming positively charged. What is the best explanation for this phenomenon?

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 electrical conductor?

Accepted Answer

Copper

Question 4

A neutral conducting sphere is brought near a positively charged rod. What happens to the charges within the sphere?

Accepted Answer

Negative charges move toward the rod and positive charges move away.

Question 5

Which process best describes charging by induction?

Accepted Answer

Separation of charges in a neutral object due to the presence of a nearby charged object, without direct contact.

Question 6

According to Coulomb's law, what is the magnitude of the force between two point charges $$q_1$$ and $$q_2$$ separated by a distance $$r in $$vacuum?

Accepted Answer

$$F = \dfrac{q_1$ q_2$}{4 \pi \$$varepsilon_0$$ r^2$}$$

Question 7

If three point charges are placed at the vertices of an equilateral triangle, how would you determine the net force on one of the charges?

Accepted Answer

Use the vector sum of the forces from the other two charges, applying the superposition principle.

Question 8

A test charge $$Q is $$placed at a point where the electric field is $$\vec{E}. $$What is the force experienced by the test charge?

Accepted Answer

$$\vec{F} = Q \vec{E}$$

Question 9

Which of the following best describes the direction of the electric field vector at a point in space?

Accepted Answer

It points from positive to negative charges.

Question 10

A long, uniformly charged rod has a linear charge density $$\lambda. $$What is the correct expression for the electric field at a distance $$r$$ from the rod (assuming $$r is $$much greater than the rod's radius)?

Accepted Answer

$$E = \dfrac{\lambda}{2 \pi \$$varepsilon_0$$ r}$$

Question 11

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

Accepted Answer

The density of electric field lines is proportional to the magnitude of the electric field.

Question 12

A parallel plate capacitor is constructed with two large plates of area $$A$$ separated by a distance $$d$$, and a charge $$+Q on $$one plate and $$-Q on $$the other. What is the surface charge density $$\sigma on $$each plate?

Accepted Answer

$$\sigma = \dfrac{Q}{A}$$

Question 13

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

Accepted Answer

It is zero.

Question 14

A charged rod is brought near a neutral metal sphere, and the sphere is then grounded. After removing the ground and the rod, what is the net charge on the sphere?

Accepted Answer

It has a net charge opposite to that of the rod.

Question 15

Which of the following integrals correctly represents the electric field at a point $$P$$ due to a continuous line charge with linear charge density $$\lambda$$?

Accepted Answer

$$\vec{E}(P) = \dfrac{1}{4 \pi \$$varepsilon_0$$} \int \dfrac{\lambda d\ell}{r^2$} \hat{r}$$

Question 16

Which of the following is a correct statement about the superposition principle in electrostatics?

Accepted Answer

The net electric field at a point is the vector sum of the fields from each charge.

Question 17

A point charge $$q is $$placed at the origin. At what distance $$r$$ from the charge does the electric field have a magnitude $$E$$?

Accepted Answer

$$r = \sqrt{\dfrac{q}{4 \pi \$$varepsilon_0$$ E}}$$

Question 18

Which of the following best explains why field lines never cross in an electric field diagram?

Accepted Answer

Because the electric field at a point can have only one direction.

Question 19

A region of space contains a uniform electric field. Which of the following statements is true about the field lines in this region?

Accepted Answer

The field lines are straight, parallel, and equally spaced.

Question 20

A student draws electric field lines for two equal but opposite point charges placed a short distance apart. Which of the following best describes the pattern of the field lines?

Accepted Answer

Field lines originate from the positive charge and terminate on the negative charge.

LEC 1: Electric Fields: Concepts, Laws, and Visualization

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