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NEET 2012
Exam
NEET
Year
2012
Subject
Physics
Chapter
Electrostatics

NEET 2012 · Physics · Electrostatics

Four point charges -Q,-q, 2 q and 2 Q are placed, one at each...

Four point charges −Q,−q,2q-Q,-q, 2 q and 2Q2 Q are placed, one at each corner of the square. The relation between QQ and qq for which the potential at the centre of the square is zero, isFour point charges -Q,-q, 2 q and 2 Q are placed, one at each corner of the square. The relation between Q and q for

Options

  1. AQ=−qQ=-q
  2. BQ=−1qQ=-\frac{1}{q}
  3. CQ=qQ=q
  4. DQ=1qQ=\frac{1}{q}

Correct answer

A. Q=−qQ=-q

Step-by-step solution

Four point charges -Q,-q, 2 q and 2 Q are placed, one at each corner of the square. The relation between Q and q for
If potential at centre is zero, then V1+V2+V3+V4=0−kQr−kqr+k2Qr+k2qr=0−Q−q+2q+2Q=0Q=−q\begin{aligned} V_1+V_2+V_3+V_4 & =0 \\ -\frac{k Q}{r}-\frac{k q}{r}+\frac{k 2 Q}{r}+\frac{k 2 q}{r} & =0 \\ -Q-q+2 q+2 Q & =0 \\ Q & =-q \end{aligned}
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