PHY 131 EXAM 1 | QUESTIONS AND
ANSWERS | 2026 UPDATE | WITH
COMPLETE SOLUTIONS
True statements about Gauss's Law - ANSWER>The electric flux passing through a Gaussian surface depends only
on the amount of charge inside that surface, not on its size or shape.
If a Gaussian surface is completely inside an electrostatic conductor, the electric field must always be zero at all
points on that surface.
Consider a spherical Gaussian surface of radius R centered at the origin. A charge Q is placed inside the sphere. To
maximize the magnitude of the flux of the electric field through the Gaussian surface, the charge should be located
- ANSWER>The charge can be located anywhere, since flux does not depend on the position of the charge as long
as it is inside the sphere.
The figure shows two unequal point charges, q and Q, of opposite sign. Charge Q has greater magnitude than
charge q. In which of the regions A, B, C will there be a point at which the net electric field due to these two
charges is zero?
fig.
--A--(G)---B---(q)--C-- - ANSWER>C
, A negative point charge Q and two unknown point charges, q1 and q2, are placed as shown in the figure. The net
electric field at the origin O is equal to zero. What is the sign of each of the point charges q1 and q2?
q1=(0,2)
Q=(3,1.5)
q2=(-3,0) - ANSWER>q1>0
q2<0
A negative charge is moving in the direction of an electric field. What can you say about the potential energy of the
system? - ANSWER>the potential energy increases
Two positive charges and a negative charge with equal magnitude q lie at the vertices of an equilateral triangle with
side a. What is the electric potential energy of the system of the three charges in terms of k, q, and a? - ANSWER>-
(kq^2)/a
An electric dipole is shown. The five points shown and the two point charges all lie in the same plane. Which point
has the most positive potential value.
fig.
ANSWERS | 2026 UPDATE | WITH
COMPLETE SOLUTIONS
True statements about Gauss's Law - ANSWER>The electric flux passing through a Gaussian surface depends only
on the amount of charge inside that surface, not on its size or shape.
If a Gaussian surface is completely inside an electrostatic conductor, the electric field must always be zero at all
points on that surface.
Consider a spherical Gaussian surface of radius R centered at the origin. A charge Q is placed inside the sphere. To
maximize the magnitude of the flux of the electric field through the Gaussian surface, the charge should be located
- ANSWER>The charge can be located anywhere, since flux does not depend on the position of the charge as long
as it is inside the sphere.
The figure shows two unequal point charges, q and Q, of opposite sign. Charge Q has greater magnitude than
charge q. In which of the regions A, B, C will there be a point at which the net electric field due to these two
charges is zero?
fig.
--A--(G)---B---(q)--C-- - ANSWER>C
, A negative point charge Q and two unknown point charges, q1 and q2, are placed as shown in the figure. The net
electric field at the origin O is equal to zero. What is the sign of each of the point charges q1 and q2?
q1=(0,2)
Q=(3,1.5)
q2=(-3,0) - ANSWER>q1>0
q2<0
A negative charge is moving in the direction of an electric field. What can you say about the potential energy of the
system? - ANSWER>the potential energy increases
Two positive charges and a negative charge with equal magnitude q lie at the vertices of an equilateral triangle with
side a. What is the electric potential energy of the system of the three charges in terms of k, q, and a? - ANSWER>-
(kq^2)/a
An electric dipole is shown. The five points shown and the two point charges all lie in the same plane. Which point
has the most positive potential value.
fig.
