Question

An electron and a proton are both released from rest 1 meter from a large stationary negative charge, considering only the force from the large stationary negative charge on the proton and electron. Which of the following is true?

• A. The magnitude of force is greater on the electron
• B. The magnitude of force is greater on the proton
• C. The magnitude of force is the same on both the electron and proton
• D. The direction of the force, but not the magnitude, is the same on both the electron and proton
  

Answer 1

Answer: (C)

The magnitude of force is the same on both the electron and proton

The electric force acting on a charged species at a finite distance is $\frac{1}{4\pi {ϵ}_0}\frac{Qq}{d^2}$

Since charge of both proton and electron is same but opposite in sign, the magnitude of force on both is same, but direction is opposite.