Q: A $$4.0-C $$charge is located $$0.45 m to $$the left of a $$+6.0-C $$charge. What is the magnitude and direction of the electrostatic force on the positive charge?

$$1.2 \times 10^9$ N, to the left

Q: A $$4.5$$-$$\muC $$charge is uniformly distributed within a sphere that has a radius of $$0.300 m. $$What is the magnitude and direction of the electric field at $$0.300 m $$from the surface of the sphere?

$$1.50 \times 10^2$ N/C, radially outward

Question 1

A conducting sphere has a net charge of $$-4.4 	imes 10$$^{-17}$$ C. What is the approximate number of excess electrons on the sphere? (Elementary charge e = 1.6$$ 	imes $$10^{-19} C)$$

Accepted Answer

$$2.8 	imes 10^5$

Question 2

When an ebonite rod is rubbed with animal fur, the rod becomes negatively charged. Which of the following best explains this observation?

Accepted Answer

Negative charges are transferred from the fur to the rod.

Question 3

A charged rod is used to induce a net uncharged metal sphere. Which one of the following statements is correct?

Accepted Answer

Both sides of the sphere will acquire equal and opposite charges.

Question 4

A neutral sodium atom has an electron charge of $$+3.2 	imes 10$$^{-19}$$ C. How many electrons must be added to make it electrically neutral?

Accepted Answer

1

Question 5

Two charged particles A and B are located near one another. Both the magnitude and direction of the force that particle A exerts on particle B is:

Accepted Answer

Dependent on the charges of A and B, and the distance between them.

Question 6

Four point charges, each of the same magnitude, with varying signs are arranged at the corners of a square. Which of the arrows labeled A, B, C, and D gives the correct direction of the net force that acts on the charge at the upper right corner?

Accepted Answer

C

Question 7

Two positive point charges $$Q$$ and $$2Q$$ are separated by a distance $$r. If $$the charge $$Q$$ experiences a force of magnitude $$F$$ when the separation is $$r$$, what is the magnitude of the force on the charge $$2Q$$ when the separation is $$2r$$?

Accepted Answer

$$F/4$$

Question 8

A charge Q exerts a 1.2 N force on another charge q. If the distance between the charges is doubled, what will be the magnitude of the force exerted on q?

Accepted Answer

0.3 N

Question 9

At what separation will two charges, each of magnitude $$6.0 \mu C$$, exert a force of $$70 N on $$one another? $$(k = 9.0 	imes 10^9$ \ \mathrm{N \cdot m^2$/C^2$$})$

Accepted Answer

$$0.18 m$$

Question 10

A $$4.0-C $$charge is located $$0.45 m to $$the left of a $$+6.0-C $$charge. What is the magnitude and direction of the electrostatic force on the positive charge?

Accepted Answer

$$1.2 	imes 10^9$ N, to the left

Question 11

In the figure, point A is a distance $$r$$ away from a point charge $$Q. $$Point B is a distance $$4r$$ away from Q. What is the ratio of the electric field at B to that at A, $$E_B/E_A$$?

Accepted Answer

$$1/16$$

Question 12

Which point (if any) in the electric field is zero N/C for the two point charges shown on the axis below?

$$+Q$$ ----------- $$-2Q$$

Accepted Answer

To the right of $$-2Q$$

Question 13

The electric field is never zero in the vicinity of three charges. Which of the following arrangements would result in this situation?

Accepted Answer

Three charges of equal magnitude and sign placed at the vertices of an equilateral triangle.

Question 14

Which of the following statements is true concerning the electrostatic charge on a conductor?

Accepted Answer

The charge is entirely on the outer surface, but is not uniformly distributed.

Question 15

The magnitude of the electric field at a distance r away from a negative point charge is $$E. $$What is the magnitude of the electric field at the same location if the magnitude of the charge is doubled?

Accepted Answer

$$2E$$

Question 16

A $$4.5$$-$$\muC $$charge is uniformly distributed within a sphere that has a radius of $$0.300 m. $$What is the magnitude and direction of the electric field at $$0.300 m $$from the surface of the sphere?

Accepted Answer

$$1.50 	imes 10^2$ N/C, radially outward

Question 17

The electric potential at a certain point in space is $$12 V. $$What is the electric potential energy of a $$-3.6 	imes 10$$^{-6}$$ C charge placed at that point?

Accepted Answer

$$-43 \ \muJ$$

Question 18

Two positive point charges are separated by a distance $$R. If $$the distance between the charges is halved, what happens to the total electric potential energy of the system?

Accepted Answer

The total electric potential energy increases by a factor of 4.

Question 19

A $$3.5-A $$current is maintained in a simple circuit with a total resistance of $$150 \Omega. $$What total charge passes through any point in the circuit during a thirty second interval?

Accepted Answer

$$105 C$$

Question 20

Suppose the human body has a resistance of $$500 \Omega. $$How much voltage would be required in order to drive a dangerous amount of current ($$0.1 A) $$through the body?

Accepted Answer

$$50 V$$

Electric Forces, Fields, Potential, and Circuits: Chapters 18–20 Study Guide

Study Guide - Practice Questions

Study Guide - Flashcards