Q: An atom contains 16 protons and 7 electrons. What is its net electric charge?

$$Q = (16 - 7) \times 1.60 \times 10$$^{-19}$$\ \text{C} = 1.44 \times 10$$^{-18}$$\ \text{C}$$

Q: How many electrons are required to decrease the charge of an object by $$16\ \mu\text{C}$$?

$$n = \frac{16 \times 10$$^{-6}$$\ \text{C}}{1.60 \times 10$$^{-19}$$\ \text{C}} = 1.0 \times 10$$^{14}$$ electrons

Question 1

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

Accepted Answer

Electric charge can only be moved from one object to another; the total charge remains constant.

Question 2

An atom contains 16 protons and 7 electrons. What is its net electric charge?

Accepted Answer

$$Q = (16 - 7) 	imes 1.60 	imes 10$$^{-19}$$\ 	ext{C} = 1.44 	imes 10$$^{-18}$$\ 	ext{C}$$

Question 3

How many electrons are required to decrease the charge of an object by $$16\ \mu	ext{C}$$?

Accepted Answer

$$n = \frac{16 	imes 10$$^{-6}$$\ 	ext{C}}{1.60 	imes 10$$^{-19}$$\ 	ext{C}} = 1.0 	imes 10$$^{14}$$ electrons

Question 4

Which material is most likely to allow the movement of electric charge?

Accepted Answer

Copper

Question 5

When a glass rod is rubbed with fur, what is the resulting charge on the rod?

Accepted Answer

The rod becomes positively charged.

Question 6

Which process results in a net charge on an object without direct contact?

Accepted Answer

Induction

Question 7

Two identical metal spheres, one with $$1\ 	ext{C}$$ and the other with $$3\ 	ext{C}$$, are brought into contact and then separated. What is the final charge on each sphere?

Accepted Answer

$$2\ 	ext{C}$$

Question 8

What is the magnitude of the force between two point charges $$q_1$$ and $$q_2$$ separated by a distance $$r$$ according to Coulomb’s Law?

Accepted Answer

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

Question 9

If the force between two charges is $$F at a $$distance $$d$$, what will the force be if the distance is doubled?

Accepted Answer

$$\frac{F}{4}$$

Question 10

A $$1.5\ \mu	ext{C}$$ charge with a mass of $$50\ 	ext{g} is $$suspended in an electric field that balances gravity. What is the required electric field magnitude?

Accepted Answer

$$E = \frac{mg}{q}$$

Question 11

What is the electric field at a distance $$r$$ from a point charge $$Q$$?

Accepted Answer

$$E = \frac{kQ}{r^2$}$$

Question 12

If the electric field at distance $$x$$ from a charge is $$20\ 	ext{N/C}$$ and at distance $$y it is$$ $$10\ 	ext{N/C}$$, what is the ratio $$x/y$$?

Accepted Answer

$$x/y = \sqrt{2}$$

Question 13

What is the direction of electric field lines for a positive point charge?

Accepted Answer

Outward from the charge

Question 14

A parallel plate capacitor has plates of area $$A$$ and charge $$Q. $$What is the electric field between the plates?

Accepted Answer

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

Question 15

What happens to the electric field between two parallel plates if the charge doubles and the area halves?

Accepted Answer

The electric field increases by a factor of 4

Question 16

A dipole consists of charges $$+q$$ and $$-q$$ separated by distance $$d. $$What is the magnitude of the dipole moment?

Accepted Answer

$$p = qd$$

Question 17

What is the potential energy of a dipole in a uniform electric field $$E at $$angle $$	heta$$?

Accepted Answer

$$U = -pE\cos	heta$$

Question 18

What is the torque experienced by a dipole in a uniform electric field $$E at $$angle $$	heta$$?

Accepted Answer

$$	au = pE\sin	heta$$

Question 19

If a mass $$m$$ with charge $$q is $$balanced horizontally in a uniform electric field at angle $$	heta$$, what is the magnitude of the electric field?

Accepted Answer

$$E = \frac{mg}{q\cos	heta}$$

Question 20

Which statement about electric field lines is correct?

Accepted Answer

Electric field lines point from positive charges to negative charges.

Electric Charge and Electric Field: Study Notes

Study Guide - Practice Questions

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