The sign of the charge mastering physics

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HW1 Due: 11:59pm on Friday, September 14, 2018

You will receive no credit for items you complete after the assignment is due. Grading Policy

Exercise 21.4

You have a pure (24-karat) gold ring with mass 10.8 . Gold has an atomic mass of 197 and an atomic number of 79.

Part A

How many protons are in the ring?

ANSWER:

Part B

What is their total positive charge?

Express your answer with the appropriate units.

ANSWER:

Part C

If the ring carries no net charge, how many electrons are in it?

ANSWER:

Exercise 21.6

Two small spheres spaced 20.0 apart have equal charge.

Part A

How many excess electrons must be present on each sphere if the magnitude of the force of repulsion between them is 3.33 10 ?

ANSWER:

Exercise 21.12

g g/mol

= np

= Q

= ne

cm

× −21 N

= ne

11/30/2018 HW1

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A negative charge of -0.510 exerts an upward 0.700- force on an unknown charge that is located 0.500 directly below the first charge.

Part A

What is the value of the unknown charge (magnitude and sign)?

Express your answer with the appropriate units.

ANSWER:

Part B

What is the magnitude of the force that the unknown charge exerts on the -0.510 charge?

Express your answer with the appropriate units.

ANSWER:

Part C

What is the direction of this force?

ANSWER:

Electric Field Conceptual Question

Part A

For the charge distribution provided, indicate the region (A to E) along the horizontal axis where a point exists at which the net electric field is zero.

If no such region exists on the horizontal axis choose the last option (nowhere).

μC N m

= q

μC

= F

upward

downward

11/30/2018 HW1

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You did not open hints for this part.

ANSWER:

Part B

For the charge distribution provided, indicate the region (A to E) along the horizontal axis where a point exists at which the net electric field is zero.

If no such region exists on the horizontal axis choose the last option (nowhere).

You did not open hints for this part.

ANSWER:

A

B

C

D

E

nowhere

11/30/2018 HW1

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Part C

For the charge distribution provided, indicate the region (A to E) along the horizontal axis where a point exists at which the net electric field is zero.

If no such region exists on the horizontal axis choose the last option (nowhere).

You did not open hints for this part.

ANSWER:

Part D

For the charge distribution provided, indicate the region (A to E) along the horizontal axis where a point exists at which the net electric field is zero.

A

B

C

D

E

nowhere

A

B

C

D

E

nowhere

11/30/2018 HW1

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You did not open hints for this part.

ANSWER:

Exercise 21.20

Two point charges are placed on the x-axis as follows: charge = 3.95 is located at 0.204 , and charge = 4.95 is at -0.295 .

Part A

What is the magnitude of the total force exerted by these two charges on a negative point charge = -5.99 that is placed at the origin?

ANSWER:

Part B

What is the direction of the total force exerted by these two charges on a negative point charge = -5.99 that is placed at the origin?

ANSWER:

A

B

C

D

E

Nowhere along the finite x axis

q1 nC x = m q2 nC x = m

q3 nC

= F N

q3 nC

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Exercise 21.24

A particle has a charge of -5.55 .

Part A

Find the magnitude of the electric field due to this particle at a point 0.350 directly above it.

Express your answer with the appropriate units.

ANSWER:

Part B

Find the direction of this electric field.

ANSWER:

Part C

At what distance from this particle does its electric field have a magnitude of 14.0 ?

Express your answer with the appropriate units.

ANSWER:

Prelecture Concept Question 21.08

Part A

to the + directionx

to the - directionx

perpendicular to the -axisx

the force is zero

nC

m

= E

up, away from the particle

down, toward the particle

N/C

= L

11/30/2018 HW1

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The strength of the electric field at a certain distance from a point charge is represented by E. What is the strength of the electric field at twice the distance from the point charge?

ANSWER:

Prelecture Concept Question 21.10

Part A

When a point charge of +q is placed on one corner of a square, an electric field strength of 2 N/C is observed at the center of the square. Suppose three identical charges of +q are placed on the remaining three corners of the square. What is the magnitude of the net electric field at the center of the square?

ANSWER:

Prelecture Concept Question 21.04

Part A

Two charged objects are separated by some distance. The charge on the first object is greater than the charge on the second object. How does the force between the two objects compare?

ANSWER:

At twice the distance, the strength of the field is E/4.

At twice the distance, the strength of the field is E/2.

At twice the distance, the strength of the field is 4E.

At twice the distance, the strength of the field is 2E.

At twice the distance, the strength of the field remains equal to E.

The magnitude of the net electric field at the center of the square is 6 N/C.

The magnitude of the net electric field at the center of the square is 4 N/C.

The magnitude of the net electric field at the center of the square is 0 N/C.

The magnitude of the net electric field at the center of the square is 8 N/C.

The magnitude of the net electric field at the center of the square is 2 N/C.

11/30/2018 HW1

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Prelecture Concept Question 21.02

Part A

A positively charged rod is brought close to one end of an uncharged metal rod but does not actually touch it. What type of charge does the end of the metal rod closest to the positively charged rod acquire?

ANSWER:

Problem 21.01

Part A

A piece of plastic has a net charge of +2.00 μC. How many more protons than electrons does this piece of plastic have? (e = 1.60 × 10-19 C)

ANSWER:

The charged objects exert electrostatic forces on each other that are equal in magnitude and opposite in direction.

The first object exerts a large electrostatic force on the second object.

The charged objects exert electrostatic forces on each other that are equal in magnitude and pointing in the same direction.

The second object exerts a large electrostatic force on the first object.

The end of the metal rod closest to the positively charged rod remains neutral.

The end of the metal rod closest to the positively charged rod can acquire either a positive or negative charge, depending on the composition of the metal.

The end of the metal rod closest to the positively charged rod acquires a positive charge.

The end of the metal rod closest to the positively charged rod acquires a negative charge.

1.25 × 1019

2.50 × 1019

2.50 × 1013

1.25 × 1013

11/30/2018 HW1

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Problem 21.03

Part A

When two point charges are 2.0 cm apart, each one experiences a 1.0-N electric force due to the other charge. If they are moved to a new separation of 8.0 cm, the electric force on each of them is closest to

ANSWER:

Problem 21.06

Part A

Charge nC is at ( m, ), charge nC is at ( , m), and charge nC is at ( , ). What is the magnitude of the net electrostatic force on the -nC charge due to the other charges? (

N · m2/C2)

ANSWER:

Part B

What is the direction of the net electrostatic force on the -nC charge due to the other charges?

ANSWER:

Score Summary: Your score on this assignment is 0.0%.

You received 0 out of a possible total of 13 points.

1.0 N.

4.0 N.

16 N.

0.25 N.

0.063 N.

= 6.0Q1 0.30 0 = −1.0Q2 0 0.10 = 5.0Q3 0 0 5.0

k = 1/4 = 8.99 ×πϵ0 10 9

N

5.0

above -axis ∘ x