Electric Charges

Open Ended

What are some similarities and differences between the electric force and the gravitational force?

Open Ended

Describe the difference between charging by friction and charging by induction, providing an example for each.

Multiple Choice

When a negatively charged rubber rod is placed near a metal sphere and the sphere is grounded, what happens to the electrons in the sphere?

• They move to the ground.

• They move towards the rubber rod.

• They stay in place.

• They are attracted to the center of the sphere.

Multiple Choice

Which of the following materials will acquire a negative charge when rubbed with glass, according to the triboelectric series?

• Silk

• Wool

• Fur

• Polyamide (6,6)

Open Ended

Explain how the concept of electron affinity is used to determine whether an object will become positively or negatively charged when rubbed with another material. Use the triboelectric series to support your answer.

Multiple Choice

Which of the following statements is TRUE about the charge on the metal bar if a positively charged glass rod is used to charge it by induction?

• It must be positive.

• It must be negative.

• It will be equal in magnitude to the charge on the glass rod.

• It will be greater in magnitude than the charge on the glass rod.

Multiple Choice

During the charging process, some electrons from the plastic are transferred to the cotton. What can you conclude about the charges of the plastic and the cotton after rubbing?

• Both become positively charged.

• Plastic becomes negatively charged, cotton becomes positively charged.

• Plastic becomes positively charged, cotton becomes negatively charged.

• Both become negatively charged.

Multiple Choice

Which of the following objects is positively charged?

• A neutral object that gained some electrons.

• An object that has more protons than electrons.

• An object that has more neutrons than electrons.

• An object which attracts neutral objects and repels a negatively charged object.

Multiple Choice

Which of the following statements is NOT TRUE about electric charges?

• Positively charged objects lost electrons.

• Positively charged object gained protons.

• Negatively charged objects gained electrons.

• Objects with like charges attract while opposite charges repel each other.

Open Ended

Explain how the magnitude of the electric force between two point charges changes if the distance between them is doubled.

Multiple Choice

Which of the following steps is necessary to find the net electric force on a charge when more than two charges are present?

• Add the magnitudes of all forces directly.

• Use the vector sum of the individual forces exerted by each charge.

• Multiply the forces by the number of charges.

• Subtract the smallest force from the largest force.

Multiple Choice

Which of the following best describes the direction of electric field lines around a positive and a negative charge?

• They point away from positive charges and toward negative charges.

• They point toward positive charges and away from negative charges.

• They form closed loops around charges.

• They always point in a circular direction.

Multiple Select

Select all the correct statements about the interaction between electric charges:

• Like charges repel each other.

• Opposite charges attract each other.

• Electric field lines cross each other.

• The strength of the electric field decreases with distance from the charge.

Open Ended

Explain how the principle of superposition is used to calculate the net electric field at a point due to multiple charges.

Multiple Choice

Which of the following steps is NOT involved in calculating the net electric field at a point due to two charges as shown in the worked example?

• Calculate the electric field produced by each charge individually.

• Add the electric fields as vectors.

• Use the Pythagorean theorem to find the resultant field.

• Ignore the direction of each field.

Multiple Choice

What happens when two charges are moved closer together?

• The electric field doubles.

• Coulomb’s law takes effect.

• The total charge increases.

• The force between the charges increases.

Multiple Choice

Which of the following is TRUE about the charge on the metal bar if a positively charged glass rod is used to charge it by induction?

• It must be positive.

• It must be negative.

• It will be equal in magnitude to the charge on the glass rod.

• It will be greater in magnitude than the charge on the glass rod.

Multiple Choice

A positively charged rod is brought close to one end of a metallic plate. What type of charge is induced on the left side of the plate?

• Positive

• Negative

• Neutral

• It depends on the separation between the rod and plate.

Open Ended

Explain how the direction of the electric field is determined around a negative charge and compare it to the direction around a positive charge.