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NEET 2007 (AIPMT) · Electrostatic Potential Energy

Electrostatic Potential Energy question from NEET 2007 (AIPMT)

Q58NEET 2007 · AIPMTMedium

Electrostatic Potential Energy

Charges +q and −- q are placed at points A and B respectively which are a distance 2L apart, C is the midpoint between A and B. The work done in moving a charge + Q along the semicircle CRD is

Figure

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Answer: (c)

  1. The semicircle is centred at B with radius LL, so D is 3L3L from A and LL from B.
  2. VC=kqL−kqL=0V_C = \frac{kq}{L} - \frac{kq}{L} = 0, VD=kq3L−kqL=−2kq3LV_D = \frac{kq}{3L} - \frac{kq}{L} = -\frac{2kq}{3L}
  3. W=Q(VD−VC)=−2qQ3⋅4πε0L=−qQ6πε0LW = Q(V_D - V_C) = -\frac{2qQ}{3\cdot4\pi\varepsilon_0 L} = -\frac{qQ}{6\pi\varepsilon_0 L}
  4. So the answer is (c).
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