ElectrostaticsHard
Question
Charges 2Q and −Q are placed as shown in figure. The point at which electric field intensity is zero will be:


Options
A.Somewhere between −Q and 2Q
B.Somewhere on the left of −Q
C.Somewhere on the right of 2Q
D.Somewhere on the right bisector of line joining −Q and 2Q
Solution

The electric field due to a point charge ′q′ at distance ′r′ from it is given as :
E =
∴ By this mathematical analogy, electric field cannot be zero in the region iii
In region ii, electric field due to both charges is added & net electric field is towards left
Along ⊥ . bisector line IV electric field due to both charges will be added vectorially & can′t be zero
∴ E.F (net) can be zero in region I only
(by mathematical analogy explained)
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