Three charge q, Q and 4q are placed in a straight line of length l at points distant 0 , 2 1 and l respectively from one end. In order to make the net froce on q zero, the charge Q must be equal to

( F net ) q = 0 ⇒ k ( 2 ℓ ) 2 Qq + k ℓ 2 4 q 2 = 0 where k = 4 π ε 0 1 ⇒ 4 Qq + 4 q 2 = 0 ⇒ Q = − q

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PhysicsElectrostaticsElectric Field & ForceMedium2 minPYQ_2020

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Three charge q, Q and 4q are placed in a straight line of length $l$ at points distant $0, \frac{1}{2}$ and $l$ respectively from one end. In order to make the net froce on q zero, the charge Q must be equal to

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Answer:

Solution:

$(F_{net})_{q} = 0$ $\Rightarrow k \frac{Qq}{( \frac{ℓ}{2} ) ^{2}} + k \frac{4 q ^{2}}{ℓ ^{2}} = 0$
$where k = \frac{1}{4 π ε _{0}} \Rightarrow 4 Qq + 4 q^{2} = 0 \Rightarrow Q = - q$

Stream:BITSATSubject:PhysicsTopic:ElectrostaticsSubtopic:Electric Field & Force

⏱ 2mℹ️ Source: PYQ_2020

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