How Well Do You Understand Electric Fields and Potential?

[anthonyluvme]

Physics Mutiple Choice Problems! Please help and explain why. Thank you :)

1. Which of the following statements is true concerning the spacing of the electric field lines in the vicinity of two point charges of equal magnitude and equal sign?
A It indicates the relative magnitude of the electric field.
B It indicates the direction of the electric field.
C It does not depend on the magnitude of the charges.
D It is large when the magnitude of the charges is large.
E It is small when the magnitude of the charges is small.

2.Which one of the following statements is true concerning the NET work done by moving an electron at constant speed between two points in an electrostatic field?
A It is always positive.
B It depends only on the displacement of the electron.
C It depends on the total distance covered.
D It is always negative.
E It is always zero.

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?
A It increases by a factor of 4.
B It remains the same.
C It is reduced to 1/2 the original value.
D It is reduced to 1/4 the original value.
E It is doubled.

4.Which one of the following statements concerning electrostatic situations is FALSE?
A Equipotential surfaces cross paths with one another.
B Equipotential surfaces are always perpendicular to E.
C It takes zero work to move a charge along an equipotential surface.
D If V is constant throughout a region of space the E must be zero in that region.
E is zero everywhere inside a conductor.

5.Which one of the following statements best describes the equipotential surfaces surrounding a point charge?
A The equipotential surfaces are concentric spheres with the charge at the center.
B The equipotential surfaces are concentric cylinders with the charge on the axis at the center.
C The equipotential surfaces are concentric cubes with the charge at the center.
D The equipotential surfaces are curved planes surrounding the charge, but only one passes through the charge.
E The equipotential surfaces are planes extending radially outward from the charge.

 

[marcusesses]

https://www.physicsforums.com/showthread.php?t=28

 

[nlightner]

1. A. It indicates the relative magnitude of the electric field. The spacing of electric field lines represents the strength of the electric field, with closer spacing indicating a stronger field.

2. E. It is always zero. When an electron is moved at constant speed in an electrostatic field, its kinetic energy remains constant, meaning no work is being done on the electron and the net work is zero.

3. D. It is reduced to 1/4 the original value. The total electric potential energy of the system is directly proportional to the distance between the charges, so reducing the distance by a factor of 2 will decrease the energy by a factor of 4.

4. A. Equipotential surfaces cross paths with one another. Equipotential surfaces are defined as surfaces where the electric potential is constant, so they cannot intersect with each other.

5. A. The equipotential surfaces are concentric spheres with the charge at the center. For a point charge, the equipotential surfaces are spherical, with the charge at the center of the spheres.