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

Question

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

Badiuddin askIITians.ismu Expert · Answer

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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Nitish Sainani · Answer

(it is disk not the spherical cap how can you take a sphere)

Carelle · Answer

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

Kushagra Madhukar · Answer

Hello student As we know total electric flux given by a point charge Q = Q/ε 0 this flux is equally distributed in a solid angle of 4π Now, if a disk makes an angle θ with the axis of charge, the solid angle covered by the disk Ω = 2π(1- cosθ) Hence electric flux through disk, ɸ = Q/4πε 0 x 2π(1- cosθ) = Q/2ε 0 x (1 – cosθ) Given, this flux is ¼ of the flux given by charge Q Hence, Q/2ε 0 x (1 – cosθ) = Q/4ε 0 or, cosθ = ½ or, θ = 60 o Hence, b/R = cos60 o or, b = R/2 or, R = 2b or, b = (b2 + r2) 1/2 /2 or, 4b2 = b2 + r2 or, r2 = 3b2 or, r = √3 b Hope it helps Regards, Kushagra

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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

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

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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

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

4 Answers

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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