three charges, each of value Q are placed at the vertex of equlilateral triangle. A fourther charge q is placed at the center of
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0
Answer:
the net force on the centred charge is zero
Answered by
1
Answer:
B
−
3
Q
3 point charges of +Q are placed on an equilateral triangle. They will repel each other and go away from each other and go away from each other. So, the charge which we want to keep in the center should be negatively charged.
Let us consider the charge at center be −q. Let the length of side of equilateral triangle is a. Consider an equilateral triangle ABC, with centroid at D.
=
a
2
kQ
2
along
AB
F
2
=
a
2
kQ
2
along
CB
F
3
=
a
2
3kQq
along
BD
in horizontal direction, for equilibrium.
F
1
cos60
∘
+F
2
=F
3
cos30
∘
⇒
a
2
kQ
2
×
2
1
+
a
2
kQ
2
=
a
2
kQq
×
2
3
⇒
2a
2
3kQ
2
=
a
2
2
3kQq
3
⇒q=
3
Q
Since q is negatively charged,
So, q=
3
−Q
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