Question

Q According to coulomb's law which of the following is correct, for the diagram given below.
1) q1q2 <0
2) q1q2 >0
3) q1q2=0
4) q1q2>100

Answer 1

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Here F12 ( F one two ) is the force acting on q1 due to q2 and F21( F two one )  is the force acting on ​q2 due to q1.

Now, here r is the distance between q1 and q2.

From the figure we can say that the direction of both the force opposite to each other.
=> F12 = - F21( ... The force is equal and opposite to each other - Newton 's third law)

Now we know that the two charges are unlike charges i.e. one charge is +ve and the other is -ve.
So (+) * (-) = (-) {using coulomb 's law ; the force is directly proportional to the product of two charges}

Now, (-) < 0
         (+) > 0

Therefore q1q2  < 0
The correct option is (a).

Answer 2

Answer:

Here F12 ( F one two ) is the force acting on q1 due to q2 and F21( F two one ) is the force acting on q2 due to q1.

Now, here r is the distance between q1 and q2.

From the figure we can say that the direction of both the force opposite to each other.

=> F12 = - F21( ... The force is equal and opposite to each other - Newton 's third law)

Now we know that the two charges are unlike charges i.e. one charge is +ve and the other is -ve.

So (+) * (-) = (-) {using coulomb 's law ; the force is directly proportional to the product of two charges}

Now, (-) < 0

(+) > 0

Therefore q1q2 < 0

The correct option is (a).