KVPY SX SB Exam 2018 Question Paper

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Question : 40 of 120

Marks: +1, -0

An electrostatic field line leaves at an angle α from point charge q1 and connects with point charge –

q_2

at anangle β(

q_1

and

q_2

are positive) (see figure below). If

q_2 =3/2 q_1

and α = 30°, then

$0° < β < 30°$
$β = 30°$
$30° < β ≤ 60°$
$60° < β ≤ 90°$

Solution:

{2 π(1 -\cosα ) }/{2 π(1 -\cosβ ) }=q_1/q_2

{2\sin^2α/2}/{2\sin^2β/2}=2/3

β ≃ 40º

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