Exam 2 Quick Quizzes

If the net flux through a gaussian surface is zero, the following four statements could be true. Which of the statements must be true?

(A) There are no charges inside the surface (B) ✅The net charge inside the surface is zero (C) The electric field is zero everywhere on the surface (D) ✅The number of electric field lines entering the surface equals the number leaving the surface

Object A has a charge of +2 μC, and object B has a charge of +6 μC. Which statement is true about the electric forces on the object?

(A) Fab = -3 Fba (B) ✅Fab = -Fba (C) 3Fab = -Fba (D) Fab = 3Fba (E) Fab = Fba (F) 3Fab = Fba

Three objects are brought close to one another, two at a time. When objects A and B are brought together, they attract. When objects B and C are brought together, they repel. Which of the following are necessarily true?

(A) Objects A and C possess charges of the same sign (B) Objects A and C possess charges of opposite sign (C) All three objects possess charges of the same sign (D) One object is neutral (E) ✅Additional experiments must be performed to determine information about the charges on the objects

Suppose a point charge is located at the center of a spherical surface. The electric field at the surface of the sphere and the total flux through the sphere are determined. Now the radius of the sphere is halved. What happens to the flux through the sphere and the magnitude of the electric field at the surface of the sphere?

(A) The flux and field both increase (B) The flux and field both decrease (C) The flux increases, and the field decrease (D) The flux decreases, and the field increases (E) ✅The flux remains the same, and the field increases (F) The flux decreases, and the field remains the same

A test charge of +3 μC is at a point P where an external electric field is directed to the right and has a magnitude of 4 x 10^6 N/C. If the test charge is replaced with another test charge of -3 μC, what happens to the external electric field at P?

(A) ✅It is unaffected (B) It reverses direction (C) It changes in a way that cannot be determined

Three objects are brought close to each other, two at a time. When objects A and B are brought together, they repel. When objects B and C are brought together they also repel. Which of the following are true?

(A) ✅Objects A and C possess charges of the same sign (B) Objects A and C possess charges of opposite sign (C) ✅All three objects possess charges of the same sign (D) One object is neutral (E) ✅Additional experiments must be performed to determine the signs of the changes

Your younger brother likes to rub his feet on the carpet and then touches you to give you a shock. While you are trying to escape the shock treatment, you discover a hollow metal cylinder in your basement, large enough to climb inside. In which of the following cases will you not be shocked?

(A) ✅You climb inside the cylinder, making contact with the inner surface, and your charged brother touches the outer metal surface (B) Your charged brother is inside touching the inner metal surface and you are outside, touching the outer metal surface (C) Both of you are outside the cylinder, touching its outer metal surface but not touching each other directly

QQ 23.5: Rank the magnitudes of the electric field at points A, B, and C

A, B, C