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BITSAT Physics Electrostatics 2024 BITSAT 2024 (Memory Based Paper 3)

BITSAT Physics Question (2024) — Solution

Question

Electric field at point (30,30,0) due to a charge of 0.008 C placed at origin will be, (coordinates are in cm )

Options

  1. A. 8000 NC ^ -1
  2. B. 4000( i + j ) NC ^ -1
  3. C. 200 2 ( i + j ) NC ^ -1
  4. D. 400 2 ( i + j ) NC ^ -1

Answer

C. 200 2 ( i + j ) NC ^ -1

Step-by-step solution

E= K q r^2 r = K q r^3 r Here, aligned r & = (x_2-x_1 )^2+ (y_2-y_1 )^2+ (z_2-z_1 )^2 \\ & = (30)^2+(30)^2+0^2 \\ & =30 2 ~cm \\ & =30 2 10^ -2 ~m aligned and q=8 10^ -3 10^ -6 C Also, r =(30 i +30 j ) 10^ -2 ~m aligned So, E & = 9 10^9 8 10^ -3 10^ -6 (30 2 10^ -2 )^3 (30 i +30 j ) 10^ -2 \\ & = 9 8 10^9 10^ -11 27 2 2 10^ -6 10^3 30( i + j ) \\ & = 9 8 10^2 3 27 2 2 ( i + j ) \\ & =200 2 ( i + j ) NC ^ -1 aligned

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