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BITSAT 2017
Exam
BITSAT
Year
2017
Subject
Physics
Chapter
Electrostatics

BITSAT 2017 · Physics · Electrostatics

Three charges are placed at the three vertices of an equilateral...

Three charges are placed at the three vertices of an equilateral triangle of side aa as shown in the figure. The force experienced by the charge placed at the vertex AA in a direction normal to BCBC is

Three charges are placed at the three vertices of an equilateral triangle of side a as shown in the figure. The force

Options

  1. AQ24πε0a2\dfrac{Q2}{4\pi{ε}_{0}a^{2}}
  2. B−Q24πε0a2- \dfrac{Q2}{4\pi{ε}_{0}a^{2}}
  3. Czero
  4. DQ22πε0a2\dfrac{Q2}{2\pi{ε}_{0}a^{2}}

Correct answer

C. zero

Step-by-step solution

Resultant force

F′=F2+F2+2FFcos120°=FF^{'} = \sqrt{F^{2} + F^{2} + 2FFcos120 °} = F~ & \left[∵ \cos 120 ° = \dfrac{- 1}{2}\right]</p><p><imgsrc="/api/proxy−image?url=https</p><p><img src="/api/proxy-image?url=https%3A%2F%2Ffirebasestorage.googleapis.com%2Fv0%2Fb%2Fquantrexacademy-app.firebasestorage.app%2Fo%2Fquestions%252Ffigs%252Fpyq%252Fbitsat%252F2ca33903-5b85-4ca6-a0d8-ece8058f4f1e-image.png%3Falt%3Dmedia&clean=1&v=wm2" data-qx-orig-src="https://firebasestorage.googleapis.com/v0/b/quantrexacademy-app.firebasestorage.app/o/questions%2Ffigs%2Fpyq%2Fbitsat%2F2ca33903-5b85-4ca6-a0d8-ece8058f4f1e-image.png?alt=media" data-qx-storage-src="https://firebasestorage.googleapis.com/v0/b/quantrexacademy-app.firebasestorage.app/o/questions%2Ffigs%2Fpyq%2Fbitsat%2F2ca33903-5b85-4ca6-a0d8-ece8058f4f1e-image.png?alt=media" style="width: 250px; height: 220px;" /></p><p>Now, from figure</p><p>F = \sqrt{F^{' 2} + F^{' ' 2} + 2F^{'}F^{' '}\cos 90 °}</p><p>Now,theforcenormalto</p><p>Now, the force normal toBCatvertexat vertexAis</p><p>is</p><p>F^{' '} = \sqrt{F^{2} - F^{' 2}} = 0~ & \left(∵ F^{'} = F\right)

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