Two equal point charges Q = + 2 µC are placed at each of the two opposite corners of a square and equal
point charges q at each of the other two corners. What must be the value of q so that the resultant force
on Q is zero ?
Answers
Answer: Let a metre the side of the side of the square.The length of a diagonal will be
2
a.The force on the positive charge Q at A due to the positive charge Q at C is F=
4πε
0
1
2a
2
Q
2
and is directed outward,as shown.In order to make net force on Q zero,the resultant of the other two force F
1
and F
2
on Q due to the charges q and q should be equal and opposite to F.Clearly F
1
and F
2
will be directed as shown and for this both q
′
should be negative.
now
F
1
=F
2
=
4πε
0
1
a
2
since F
1
and F
2
are at right angles, their resultant is
F
12
=
4πε
0
1
a
2
2
For the equilibrium of Q, we musst have
F=F
12
But Q+
2
μC
∴q=−
2
2
2
μC
=−0.5μC
Answer:
I hope it helps thank you
