A proton and an electron are released from rest at the origin in positive x-direction where electric potential increases along the x axis.
What can you say about their change in speed?
Answer & explanation
Correct answer: option 4
The correct answer is Option 4: the speed of proton decreases and the speed of electron increases
The electric field is directed toward the negative x-axis because potential increases along the x-axis.
The proton (positive charge), moving in +x, experiences a force in –x, so it decelerates.
The electron (negative charge) experiences a force in +x (same as its motion), so it accelerates.
Thus, the proton’s speed decreases and the electron’s speed increases.