Courses
Courses for Kids
Free study material
Offline Centres
More
Store Icon
Store
seo-qna
SearchIcon
banner

If two charges of 1 coulomb each are placed 1 km apart, the force between them will be
(1)9×103N (2)9×103 (3)1.1×104 (4)106

Answer
VerifiedVerified
437k+ views
1 likes
like imagedislike image
Hint: We will use the formula of coulomb's electrostatic force between two charges. By substituting the values of k, charge and the distance between them we can find the value of Force between the two charges.
Formula: F=kq1q2r2

Complete answer:
We know that electrostatic force acts between two stationary electrically charged particles separated by a distance ‘r’. This force is also called coulomb's force. It is given by the formula
F=kq1q2r2 ---------(1)
Where k is the coulomb's constant, q1and q2is the charge in coulombs.
In the question, it is given that q1=q2=1C
And the charges are placed 1km apart, so r=1km=1000m
The value of coulomb’s constant k=9×109Nm2C2
Substituting above values in equation (1), we get
9×109×1×1(1000)2N9×109×106N9×103NF=9×103N
So, If two charges of 1 coulomb are placed 1 km apart, the force between them will be9×103N.

So, Option (1) is correct.

Additional information:
Electrostatic force is an attractive or repulsive force which acts between stationary electrically charged particles. The electric force between a stationary charged body is conventionally known as the electrostatic force or Coulomb’s force.
1 Coulomb charge is equal to the amount of charge from a current of one ampere flowing for one second. It can also be defined as One coulomb is equal to the charge on 6.241×1018 protons. The charge on 1 proton is 1.6×1019 C.

Note:
In the formula for electrostatic force, ‘k’ is the proportionality constant also known as coulomb’s constant.
k=14πξ0=9×109Nm2C2ξ0=8.85×1012C2/Nm2
ξ0 is known as the permittivity of free space.
One must remember all these values while solving questions of electrostatics.