Q: What is the value of the elementary charge $$e in $$Coulombs?

$$e = 1.6 \times 10$$^{-19}$$\ \mathrm{C}$$

Question 1

Which of the following statements about electric charge is correct?

Accepted Answer

The charge of a proton is positive and equal in magnitude to the charge of an electron, which is negative.

Question 2

What is the value of the elementary charge $$e in $$Coulombs?

Accepted Answer

$$e = 1.6 	imes 10$$^{-19}$$\ \mathrm{C}$$

Question 3

Which of the following materials is most likely to be a conductor?

Accepted Answer

Copper

Question 4

A laser printer uses static electricity to attract toner particles to paper. Which property of electric charge is most directly involved in this process?

Accepted Answer

Attraction and repulsion between charges

Question 5

According to Coulomb's Law, what happens to the force between two point charges if the distance between them is doubled?

Accepted Answer

The force decreases by a factor of 4.

Question 6

Given two charges $$q_1 = 2$$\ \mu\mathrm{C}$$ and q_2$ = -3\ \mu\mathrm{C}$$ separated by $$r = 0.05\ \mathrm{m}$$, what is the magnitude of the force between them? Use $$k = 8.99 	imes 10^9$\ \mathrm{N\cdot m^2$/C^2$$}$.

Accepted Answer

$$F = 2.16\ \mathrm{N}$$

Question 7

Three charges are placed at the vertices of an equilateral triangle. If all charges are positive and equal in magnitude, what is the direction of the net electric force on any one charge?

Accepted Answer

Away from the center of the triangle

Question 8

Which equation correctly expresses Coulomb's Law for the magnitude of the electric force between two point charges?

Accepted Answer

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

Question 9

A positive test charge is placed in an electric field. In which direction does the force on the test charge act?

Accepted Answer

In the direction of the electric field

Question 10

If the net electric force on a charge is zero, which of the following must be true?

Accepted Answer

The vector sum of all individual forces acting on the charge is zero.

Question 11

Which of the following is the correct expression for the electric field $$E$$ created by a point charge $$q at a $$distance $$r$$?

Accepted Answer

$$E = k \frac{q}{r^2$}$$

Question 12

A negative test charge is placed in an electric field. In which direction does the force on the test charge act?

Accepted Answer

Opposite to the direction of the electric field

Question 13

Which of the following best describes the principle of superposition for electric fields?

Accepted Answer

The net electric field is the vector sum of the individual fields.

Question 14

A Van de Graaff generator is used in a physics demonstration. Which concept does this device best illustrate?

Accepted Answer

Generation and storage of static electric charge

Question 15

If $$q_1 = 1.0$$\ \mu\mathrm{C}$$, q_2$ = -2.0\ \mu\mathrm{C}$$, and $$q_3 = 3.0$$\ \mu\mathrm{C}$$ are placed as shown in the diagram with r$$_{13} = 5\ \mathrm{cm}$$ and r$$_{23} = 4\ \mathrm{cm}$$, what is the first step to find the net force on q_3$?

Accepted Answer

Calculate the individual forces on $$q_3$$ due to $$q_1$$ and $$q_2$$ using Coulomb's Law.

Question 16

Which of the following is the correct value for the Coulomb constant $$k$$?

Accepted Answer

$$k = 8.99 	imes 10^9$\ \mathrm{N\cdot m^2$/C^2$$}$

Question 17

Which of the following is NOT a real-world application of static electricity?

Accepted Answer

Electric motor

Question 18

If balloon B is known to be positively charged and balloon A is attracted to balloon B, what can you conclude about the charge on balloon A?

Accepted Answer

Balloon A must be negatively charged.

Question 19

Which property of charge ensures that the total charge in an isolated system remains constant?

Accepted Answer

Conservation of charge

Electric Forces and Electric Field: Fundamental Concepts in Physics II

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