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Electric Potential
I Electric Potential Energy
1. A negative test charge q = -0.6 C moves through a uniform electric field of magnitude 5 N/C from
point A to point B to point C, as in the picture below.
A
E = 5 N/C
0.5m
B
0.5m
C
A. What is the force on the charge due to the electric field as it moves from point A to point B?
from B to C?
B. Recall the definition of work from Physics 1. How much work was done by the electric net force
as the charge moves from point A to point B? from B to C?
C. The electric force is a conservative force so there is a potential energy associated with it. What is
the change in electric potential energy of the test charge as it moves from A to B? from B to C?
2. Three protons are being held at the corners of an equilateral triangle with sides of length 0.25
meters?
A. What is the potential energy of the arrangement?
B. If the three are released simultaneously, what is the speed of each on when they are very far
apart?
II Electric Potential (Voltage)
1. Consider the definition of electric potential.
A. How is electric potential different from electric potential energy?
B. Look again at problem I.1.
1. What is the difference in potential from point A to point B, and which point is at a higher
potential?
2. What is the difference in potential from point B to point C, and which point is at a higher
potential?
2. Four charges are arranged on the corners of a square with sides of length 0.25 meters.
A. What is the electric field at the center of the square?
+4 μC
-2 μC
B. What is the electric potential at the center of the square?
-2 μC
+4 μC
3. An electron traveling at a speed v passes through a potential difference ∆V = +2 V. Does the
electron speed up, slow down, or continue at constant speed?
4. Consider the diagram of equipotential planes below. The planes are separated by 0.04 m.
A. What is the magnitude and direction of the electric field in the region?
B. A proton is released from rest at point B. What direction will it move, or will it stay stationary?