Ten positively charged particles are kept fixed on the x-axis at points x = 10 cm, 20 cm 30 cm, …., 100 cm. The first particle has a charge 1.0 × 10–8 C, the second 8 × 10–8 C, the third 27 × 10–8 C and so on. The tenth particle has a charge 1000 × 10–8 C. Find the magnitude of the electric force acting on a 1C charge placed at the origin.
Given:
Charge on the ith particle ,
Distance of ith particle from origin, 
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Formula used:
By Coulomb’s law, the electric force is given by:
Where ϵ0 is the permittivity of free space
q1 and q2 are the magnitude of charges
r is the distance of separation between the charges
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Magnitude of force on the 1C charge due to ithparticle is given by:
(Here, q1 =
, 
and 
)
Substituting the values, we get
All the forces are in negative-x direction. Hence, we can simply add them up to get the magnitude of net force.
