Question

10C charge is divided into two parts and kept at a distance 1m apart. What is the ratio of the two parts such that repulsive force between them is maximum?
i.1:2
ii.1:1
iii.2:1
iv.3:5​

Answer 1

Explanation:

Let one part of the charge be q. Thus other part of the charge is Q−q

From Coulomb's law:

Electrostatic force between them F=

r

2

kq(Q−q)

Step 2: Condition of maximum force

For maximum force,

dq

dF

=0

∴

dq

d

(

r

2

kq(Q−q)

)=0

Or,

dq

d

(qQ−q

2

)=0

Or, Q−2q=0

⇒ q=

2

Q

Hence force between them is maximum if the two parts have equal charge Q/2 each. So, Option A is correct