Directions : The following question contains
statemen-1 and statement -2 of the four choices given, choose the one that best describes the two statements.
statemen-1 For a mass M kept at the centre of a cube of side a The flux of gravitational field passing through its sides is
statement -2 If the direction of a field due to a point source is radial and its dependence on the distance r from the source is given as , its flux through a closed surface depends only on the strength of the source enclosed by the surface and not on the size or shape of the surface
statemen-1 is true ,and statement -2 false .
statemen-1 is false ,and statement -2 true .
statement-1 is true ,and statement -2 true ;
statement -2 is a correct explanation for statement -1
statemen-1 is true ,and statement -2 true ;
statement -2 is not a correct explanation for statement -1
As we learnt in
Every line passing through has to pass through
, whether
is a cube or any surface. It is only for Gaussian surface, the lines of field should be normal. Assuming the mass is a point mass.
,
Here s a cube. As explained earlier, whatever be the shape, all the lines passing through
are passing through
, although all the lines are not normal.
Statement 2 is correct because when the shape of the earth is spherical, area of the Gaussian surface is . This ensures inverse square law.
Let A be the Guassion surface enclosing a sperical charge Q.
Everyline passing through A has pass through B, whether B is a cube or any surface, it is only for guassion surface, the lines of fixed should be normal, Assuming the mass is a point mass.
thus
Here B is a cube. As explained earlier, whatever be the shape, all the lines passing through A are passing through B. Although all the lines are not normal.
Statement 2 is covered because when the shape of the earth is spherical, area of the gaussian surface is
Option 1)
statemen-1 is true ,and statement -2 false .
Incorrect option
Option 2)
statemen-1 is false ,and statement -2 true .
Incorrect option
Option 3)
statement-1 is true ,and statement -2 true ;
statement -2 is a correct explanation for statement -1
Correct option
Option 4)
statemen-1 is true ,and statement -2 true ;
statement -2 is not a correct explanation for statement -1
Incorrect option
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