In a certain region of space, a uniform electric field is in the x direction. A
ID: 2167597 • Letter: I
Question
In a certain region of space, a uniform electric field is in the x direction. A particle with negative charge is carried from x = 20.0 cm to x = 60.0 cm.(i) Does the electric potential energy of the chargefield increase, remain constant, decrease, or change unpredictably?
a. It increases.
b. It remains constant.
c. It decreases.
d. It changes unpredictably.
(ii) Has the particle moved to a position where the electric potential is higher than before, unchanged, lower than before, or unpredictable?
a. The potential is higher than before.
b. The potential is unchanged.
c. The potential is lower than before.
d. The change in potential is unpredictable.
---- a brief explanation of the concept is appreciated! -----
Explanation / Answer
(i) the potential energy increases The force on a positive charge would be along the + x-axis so the force on a negative charge is directed along the negative x-axis (Electric fields are directed "away" from + charges) Work is done on the negative charge so the potential energy increases (ii) the electric potential is lower at +60 than + 20 Electric potential is defined as the work done moving a + charge from infinity to the point being considered It would take work to move a + charge from +60 to + 20 so the electric potential is higher at +20 than at +60