Question

two point charges Q1 and Q2 are placed close to each other. what is the nature of the force between them when Q1 Q2<0

Answer 1

Q1.Q2 is less than zero.
It means, If Q1<0, thenQ2>0 or
if Q1>0, then Q2 <0.
So, Q1 and Q2 and opposite charges.
The nature of force between them will be attractive.
Opposite charges attract each other.

Answer 2

Answer: The force nature between the two charges are attractive.

Solution:

The two charged point charges are given which are placed closely, the nature of the charge can thus be known as follows –

Given:  First charge = Q1

            Second charge = Q2, Q1. Q2 < 0

The given relation implies that the product of Q1 and Q2 is zero. Hence, Q1 must be less than zero and Q2 must be more than zero .Or the other case could be that Q1 must be more than zero and Q2 must be less than zero.

Therefore, Q1 > 0 and Q2 < 0 or, Q1 < 0 and Q2 > 0

Q1 and Q2 are charges of opposite nature as one must be negative due to less than zero magnitude. Hence due to the nature of charge being negative and positive signifying opposite charges.  

The nature of force between them will attractive as charges are unlike, because opposite charges attracts.