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Dinesh Gupta Grade: 12

a point charge q is located on axis of disc of radius r at distance b from the plane of disc.if one-fourth of electric flux from charge passes through disc then.......
(a)r = b    (b)r = 2b

7 years ago

Answers : (3)

Badiuddin askIITians.ismu Expert
147 Points

Dear Dinesh

Draw a sphere whose center is at a distance b from the disk and which cover the disk



we know that flux throug a segment which makes an angel  θ at the center is

Φ=Q/2ε (1-cosθ)


where cosθ = b/(b2+r2)1/2

given flux passes in 1/4 th

so Q/2ε (1-cosθ)  =Q/4ε

    1-cosθ = 1/2

     cosθ =1/2

  b/(b2+r2)1/2 =1/2

  r =√3 b

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7 years ago
Nitish Sainani
24 Points
(it is disk not the spherical cap how can you take a sphere)

one year ago
13 Points
										A 1000w laser beam is concentrated by a Lens of a cross-sectional area of 10^-5 cm^2 . find the corresponding amplitude of the electric field
5 months ago
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