Answer:
Therefore the magnitude of required electric force is 292.864×10⁻⁵ N.
Explanation:
The number of proton of iron is 26.
C is the charge of each proton.
Total charge of 26 proton is =(26×1.6×10⁻¹⁹) C
=41.6×10⁻¹⁹ C
The charge of innermost electron is = -
C
Coulomb's Law:
The attraction or repulsion force of two charges is
- directly proportional to the product of the charges.
- inversely proportion to the square of distance
Let
be two positive charge and the distance between the charges be r
Then F∝
and 
Therefore,

Here
= -
C and
=41.6×10⁻¹⁹ C
r = 1.5× 10⁻¹² m
K= 9.9× 10⁹C²N⁻¹m⁻²
Therefore
N
= -292.864×10⁻⁵ N
The mins sign shows the direction of the force.
Magnitude of electric force is only the numerical value of the force.
Therefore the magnitude of required electric force is 292.864×10⁻⁵ N.