Question

A proton with an initial speed of 400,000 m/s is brought to rest by an electric field. Did the proton move into a region of higher potential or lower potential? a. Because the proton is a negative charge and it accelerates as it travels, it must be moving from a region of lower potential to a region of higher potential. b. Because the proton is a positive charge and it slows down as it travels, it must be moving from a region of lower potential to a region of higher potential. c. Because the proton is a positive charge and it slows down as it travels, it must be moving from a region of higher potential to a region of lower potential. d. Because the proton is a negative charge and it accelerates as it travels, it must be moving from a region of higher potential to a region of lower potential.

Answer 1

A proton is initially moving at high speed

$v = 400000 m/s$

so here initially proton is having high speed and high kinetic energy

now this proton comes to rest by external electric field

so the potential energy of proton will increase or we can say that kinetic energy will convert into electrostatic potential energy

so here the proton must have to move at higher potential region

so here correct answer must be

b. Because the proton is a positive charge and it slows down as it travels, it must be moving from a region of lower potential to a region of higher potential.