10-15 is not the order of strength of nuclear force.........it is the distance in meters up to which it is effective b/w the particles.........and the ans. to ur qn. is ~because of nuclear forces~ .......nuclear forces are much stronger than electrostatic forces......that is the reason why protons exist together inside the nucleus(it can also be explained through pi-meson theory)...............got it?
neutral species donot produce electric field , whatever force of attraction is there b/w the two neutrons would be only "gravitational" forece of attraction. Not electrostatic.
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