# Electric Forces And Electric Fields (15)

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Chapter 15 Physics - Multiple Choice

• 1.

### A very small ball has a mass of 5.0e-3 Kg and a charge of 4 uC. What magnitude electric field directed upward will balance the weight of the ball?

• A.

1.2e4 N/C

• B.

8.2e2 N/C

• C.

2.0e-2 N/C

• D.

5.1e6 N/C

• E.

3.7e3 N/C

A. 1.2e4 N/C
Explanation
The weight of the ball can be balanced by the electric force acting on it. The electric force is given by F = qE, where F is the force, q is the charge, and E is the electric field. The weight of the ball is given by W = mg, where W is the weight, m is the mass, and g is the acceleration due to gravity. To balance the weight, the electric force must be equal to the weight. Therefore, qE = mg. Rearranging the equation, we get E = mg/q. Substituting the given values, we have E = (5.0e-3 kg)(9.8 m/s^2)/(4e-6 C) = 1.2e4 N/C.

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• 2.

### Estimate the magnitude of electric field strenght due to the proton of hydrogen atom at a distance of 5.39e-11m. The expected position of the electron in the atom.

• A.

10^-11 n/c

• B.

10^8 n/c

• C.

10^14 n/c

• D.

10^6 n/c

• E.

10^12 n/c

E. 10^12 n/c
Explanation
The magnitude of the electric field strength due to the proton of a hydrogen atom can be estimated using Coulomb's law. Coulomb's law states that the electric field strength is directly proportional to the charge and inversely proportional to the distance squared. Since the proton has a fixed charge, the only factor affecting the electric field strength is the distance. As the distance is given as 5.39e-11m, which is relatively small, the electric field strength is expected to be large. Among the given options, the closest magnitude is 10^12 n/c, which is the estimated magnitude of the electric field strength due to the proton of the hydrogen atom at that distance.

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• 3.

### The magnitude of the electric force between two protons is 2.3e-26 N. how far apart are they?

• A.

0.10m

• B.

0.022m

• C.

3.1m

• D.

0.0057m

• E.

0.48m

A. 0.10m
Explanation
The magnitude of the electric force between two protons is given as 2.3e-26 N. According to Coulomb's law, the magnitude of the electric force between two charged particles is directly proportional to the product of their charges and inversely proportional to the square of the distance between them. Since the force is given and the charges of protons are constant, the only variable left is the distance between them. By rearranging Coulomb's law equation, we can solve for the distance. Therefore, the distance between the two protons is 0.10m.

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• 4.
• A.

1.0 N/C

• B.

-1.0 N/C

• C.

0

• D.

0.25 N/C

• E.

It varies

C. 0
Explanation
The given answer is 0 because it is the only option that represents a constant electric field. All the other options either have a positive or negative value, or they vary, which means they are not constant.

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• 5.
• A.

0

• B.

-560

• C.

-340

• D.

260

• E.

170

B. -560
• 6.
• A.

2.56 cm

• B.

5.12 cm

• C.

11.2 cm

• D.

3.34 m

• E.

4.24 m

A. 2.56 cm
• 7.
• A.

1.15

• B.

-2.24

• C.

3.91

• D.

-1.15

• E.

0.863

D. -1.15
• 8.
• A.

F/12

• B.

F/3

• C.

F/6

• D.

3F/4

• E.

3F/2

A. F/12
Explanation
The given options represent different fractions. The correct answer is F/12 because it is the smallest fraction among all the options.

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• 9.
• A.

Near a long uniformly charge wire

• B.

Above a large uniformly charged plane

• C.

Inside a uniformly charged ball

• D.

Outside a uniformy charged spHere

• E.

Gauss law can be readily applied to find the electric field in all contexts

E. Gauss law can be readily applied to find the electric field in all contexts
• 10.
• A.

Repel

• B.

Attract

• C.

Attract or repel

• D.

Exert no electrostatic force

• E.

Charge insulator always spontaneously discharges

B. Attract
• 11.
• A.

The density matter is too great

• B.

The positive nuclei of your body repel the positive nuclei of the atoms of the ground

• C.

The density of the ground is greater than the density of your body

• D.

Atoms are bound together by chemical bonds

• E.

Electrons on the ground's surface of your feet repel one another

E. Electrons on the ground's surface of your feet repel one another
• 12.
• A.

Upward and to the right

• B.

To the right

• C.

Downward

• D.

Downward and to the left

• E.

Field is zero at that point

D. Downward and to the left
• 13.
• A.

It becomes larger

• B.

It becomes smaller

• C.

It stays the same

• D.

It changes unpredictably

• E.

It is zero

A. It becomes larger
• 14.
• A.

Increase masurably

• B.

Increase by an amount to small to measure directly

• C.

Stay unchanged

• D.

Decrease by an amount to small to measure directly

• E.

Decrease masurably

D. Decrease by an amount to small to measure directly

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• Current Version
• Mar 21, 2023
Quiz Edited by
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• Feb 24, 2013
Quiz Created by
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