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JEE Main20205 Sep 2020Evening ShiftPhysicsElectrostaticsActual

Ten charges are placed on the circumference of a circle of radius R with constant angular separation between successive charges. Alternate charges 1 , 3 , 5 , 7 , 9 have charge ( + q ) each, while 2 , 4 , 6 , 8 , 10 have charge ( – q ) each. The potential V and the electric field E at the centre of the circle are respectively : (Take V = 0 at infinity)

Options

  1. AV = 10 q 4 π ϵ 0 R ; E = 0
  2. BV = 0 , E = 10 q 4 π ϵ 0 R 2
  3. C  V = 0 ;   E = 0
  4. DV = 10 q 4 π ϵ 0 R ; E = 10 q 4 π ϵ 0 R 2

Correct answer

C.   V = 0 ;   E = 0

Step-by-step solution

v net = 5 kq R + 5 k ( - q ) R v net = 0 ,   Q net = 0 E net = 0 , by symmetry

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