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GATE 2017 EE – Question 15

Electromagnetic Fields · Coulomb's Law, Electric Field Intensity, Electric Flux Density, Gauss's Law, Divergence · 1 mark · Multiple choice

Consider an electron, a neutron and a proton initially at rest and placed along a straight line such that the neutron is exactly at the center of the line joining the electron and proton. At $t = 0$, the particles are released but are constrained to move along the same straight line. Which of these will collide first?

  1. the particles will never collide
  2. all will collide together
  3. proton and neutron
  4. electron and neutron

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Show answer and explanation

Correct answer: (D) electron and neutron

Explanation

The electron and the proton attract each other, and the neutron feels no electric force. The electron has a much smaller mass, so it accelerates much more than the proton and reaches the middle first, where it meets the neutron.