Physics Quiz: Can You Pass?

1. Three objects have a net charge. Objects A and B attract one another. Objects B and C also attract one another, but objects A and C repel one another. Which one of the following table entries is a possible combination of the signs of the net charges on these three objects?

A: +B: +C: -

A: -B: +C: +

A: +B: -C: -

A: -B: +C: -

A: -B: -C: +

Objects A and C repel one another, which means they have opposite charges. Objects B and C attract one another, which means they have opposite charges. Objects A and B attract one another, which means they have opposite charges. Therefore, a possible combination of the signs of the net charges on these three objects is A: - , B: + , C: -.

Explanation

Objects A and C repel one another, which means they have opposite charges. Objects B and C attract one another, which means they have opposite charges. Objects A and B attract one another, which means they have opposite charges. Therefore, a possible combination of the signs of the net charges on these three objects is A: - , B: + , C: -.

2. Complete the following statement: When a glass rod is rubbed with silk cloth, the rod becomes positively charged as

Positive charges are transferred from the silk to the rod.

Negative charges are transferred from the rod to the silk.

Positive charges are created on the surface of the rod.

Negative charges are transferred from the silk to the rod.

Positive charges are transferred from the rod to the silk.

When a glass rod is rubbed with silk cloth, the rod becomes positively charged as negative charges are transferred from the rod to the silk.

Explanation

When a glass rod is rubbed with silk cloth, the rod becomes positively charged as negative charges are transferred from the rod to the silk.

3. Two positive point charges are separated by a distance R. If the distance between the charges is reduced to R/2, what happens to the total electric potential energy of the system?

The total electric potential energy is doubled.

The total electric potential energy remains the same.

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

The total electric potential energy is reduced to one-half of its original value.

The total electric potential energy is reduced to one-fourth of its original value.

When the distance between the charges is reduced to half, the electric potential energy of the system increases. This is because the potential energy is inversely proportional to the distance between the charges. As the distance decreases, the potential energy increases. In this case, since the distance is reduced to half, the potential energy doubles.

Explanation

When the distance between the charges is reduced to half, the electric potential energy of the system increases. This is because the potential energy is inversely proportional to the distance between the charges. As the distance decreases, the potential energy increases. In this case, since the distance is reduced to half, the potential energy doubles.

4. 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 independent of

The sign of charge B.

The sign of charge A.

The distance between A and B.

The magnitude of the charge on B.

The magnitude and direction of the force are dependent on all of the choices.

The magnitude and direction of the force between charged particles A and B depend on all of the choices given. This means that the force is independent of the sign of charge B, the sign of charge A, the distance between A and B, and the magnitude of the charge on B. In other words, the force between the particles is determined by multiple factors and is not affected by any one specific factor.

Explanation

The magnitude and direction of the force between charged particles A and B depend on all of the choices given. This means that the force is independent of the sign of charge B, the sign of charge A, the distance between A and B, and the magnitude of the charge on B. In other words, the force between the particles is determined by multiple factors and is not affected by any one specific factor.

5. Two uncharged, conducting spheres, A and B, are held at rest on insulating stands and are in contact. A positively charged rod is brought near sphere A as suggested in the figure. While the rod is in place, someone moves sphere B away from A. How will the spheres be charged, if at all?

Sphere A: PositiveSphere B: Positive

Sphere A: PositiveSphere B: Negative

Sphere A: NegativeSphere B: Positive

Sphere A: NegativeSphere B: Negative

Sphere A: ZeroSphere B: Zero

When the positively charged rod is brought near sphere A, it induces a separation of charges in sphere A. The negative charges in sphere A are attracted to the rod, leaving the positive charges behind. This results in sphere A becoming negatively charged. When sphere B is moved away from sphere A, there is no influence of the rod on sphere B. Therefore, sphere B remains uncharged. Hence, the spheres will be charged as follows: Sphere A will be negatively charged, and sphere B will be uncharged.

Explanation

When the positively charged rod is brought near sphere A, it induces a separation of charges in sphere A. The negative charges in sphere A are attracted to the rod, leaving the positive charges behind. This results in sphere A becoming negatively charged. When sphere B is moved away from sphere A, there is no influence of the rod on sphere B. Therefore, sphere B remains uncharged. Hence, the spheres will be charged as follows: Sphere A will be negatively charged, and sphere B will be uncharged.

6. Complete the following statement: The electron volt is a unit of

Energy.

Electric field strength.

Electric force.

Electric potential difference.

Electric power.

The electron volt is a unit of energy because it measures the amount of energy that an electron gains or loses when it moves through an electric potential difference of one volt. It is commonly used in physics and related fields to describe the energy levels and interactions of subatomic particles. Other options such as electric field strength, electric force, electric potential difference, and electric power are not correct because they represent different concepts and units of measurement in electromagnetism.

Explanation

The electron volt is a unit of energy because it measures the amount of energy that an electron gains or loses when it moves through an electric potential difference of one volt. It is commonly used in physics and related fields to describe the energy levels and interactions of subatomic particles. Other options such as electric field strength, electric force, electric potential difference, and electric power are not correct because they represent different concepts and units of measurement in electromagnetism.

7. Which one of the following statements is true concerning the work done by an external force in moving an electron at constant speed between two points in an electrostatic field?

The work done is always zero joules.

The work done is always positive.

The work done only depends on the speed of the electron.

The work done depends on the total distance covered.

The work done depends only on the displacement of the electron.

The work done by an external force in moving an electron at constant speed between two points in an electrostatic field depends only on the displacement of the electron. This means that the amount of work done is independent of the path taken by the electron or the total distance covered. The work done is determined solely by the initial and final positions of the electron, regardless of the speed at which it is moving.

Explanation

The work done by an external force in moving an electron at constant speed between two points in an electrostatic field depends only on the displacement of the electron. This means that the amount of work done is independent of the path taken by the electron or the total distance covered. The work done is determined solely by the initial and final positions of the electron, regardless of the speed at which it is moving.

8. Which one of the following statements best explains why it is possible to define an electrostatic potential in a region of space that contains an electrostatic field?

Work must be done to bring two positive charges closer together.

Like charges repel one another and unlike charges attract one another.

A positive charge will gain kinetic energy as it approaches a negative charge.

The work required to bring two charges together is independent of the path taken.

A negative charge will gain kinetic energy as it moves away from another negative charge.

The correct answer explains that it is possible to define an electrostatic potential in a region of space that contains an electrostatic field because the work required to bring two charges together is independent of the path taken. This means that the amount of work needed to move the charges from one point to another is the same regardless of the specific route taken. This allows for the calculation of a consistent electrostatic potential in the region.

Explanation

The correct answer explains that it is possible to define an electrostatic potential in a region of space that contains an electrostatic field because the work required to bring two charges together is independent of the path taken. This means that the amount of work needed to move the charges from one point to another is the same regardless of the specific route taken. This allows for the calculation of a consistent electrostatic potential in the region.