Download, print and study this document offline |
Page 1 Edurev123 7. Gauss-Divergence Theorem Stoles Theorem and Green’s to Identity 7.1 Find the work done in moving the particle on 2 round the ellipse ?? ?? ???? + ?? ?? ???? =?? ,?? = ?? under the field of force given by ???? =(?? ?? -?? +?? )??ˆ+(?? +?? -?? )??ˆ+(?? ?? -?? ?? +?? ?? )??ˆ (2009 : 20 Marks) Solution: Let ?? : ?? 2 25 + ?? 2 16 =1,?? =0 denote the ellipse. Work done =? ?? ?? ? ·?? ?? By Stoke's theorem ? ?? ?? ·?? ?? =?? ?? (?×?? )·??ˆ???? where ?? is the surface of the ellipse ?×?? = | | ??ˆ ??ˆ ??ˆ ? ??? ? ??? ? ??? 2?? -?? +?? ?? +?? -?? 3?? -2?? +4?? | | =-??ˆ-2??ˆ+2??ˆ For. Snormal is along positive z-axis ? ??ˆ =??ˆ (?×?? )·??ˆ =2 ? ?? ?? ?(?×?? )·??ˆ???? =?? ?? ?2???? =2× Area of ellipse =2?????? =2?? ·5·4 =40?? 7.2 Using divergent theorem evaluate ? ?? ????? ·?? ???? where ???? =?? ?? ??ˆ+?? ?? ??ˆ+?? ?? ??ˆ and ?? is the surface of the sphere ?? ?? +?? ?? +?? ?? =?? ?? . (2009 : 20 Marks) Solution: Page 2 Edurev123 7. Gauss-Divergence Theorem Stoles Theorem and Green’s to Identity 7.1 Find the work done in moving the particle on 2 round the ellipse ?? ?? ???? + ?? ?? ???? =?? ,?? = ?? under the field of force given by ???? =(?? ?? -?? +?? )??ˆ+(?? +?? -?? )??ˆ+(?? ?? -?? ?? +?? ?? )??ˆ (2009 : 20 Marks) Solution: Let ?? : ?? 2 25 + ?? 2 16 =1,?? =0 denote the ellipse. Work done =? ?? ?? ? ·?? ?? By Stoke's theorem ? ?? ?? ·?? ?? =?? ?? (?×?? )·??ˆ???? where ?? is the surface of the ellipse ?×?? = | | ??ˆ ??ˆ ??ˆ ? ??? ? ??? ? ??? 2?? -?? +?? ?? +?? -?? 3?? -2?? +4?? | | =-??ˆ-2??ˆ+2??ˆ For. Snormal is along positive z-axis ? ??ˆ =??ˆ (?×?? )·??ˆ =2 ? ?? ?? ?(?×?? )·??ˆ???? =?? ?? ?2???? =2× Area of ellipse =2?????? =2?? ·5·4 =40?? 7.2 Using divergent theorem evaluate ? ?? ????? ·?? ???? where ???? =?? ?? ??ˆ+?? ?? ??ˆ+?? ?? ??ˆ and ?? is the surface of the sphere ?? ?? +?? ?? +?? ?? =?? ?? . (2009 : 20 Marks) Solution: By gauss divergence theorem ?? ?? ??? ·?? ?? =?? ?? ?(?·?? )???? ?·?? =? ? ??? ??ˆ·?? =3?? 2 +3?? 2 +3?? 2 =3(?? 2 +?? 2 +?? 2 ) ?? is surface of sphere ?? 2 +?? 2 +?? 2 =?? 2 . ??? is the volume compressing the whole sphere. ?? ?? ??? ·?? ?? =?? ?? ?(?·?? )???? =? 1(3(?? 2 +?? 2 +?? 2 )???? Converting to spherical polar coordinates. ?? 2 +?? 2 +?? 2 =?? 2 ???? =?? 2 sin ?????????????? ?? =? ? 2?? ?? =0 ?? ? 2?? ?? =0 ?? ? ?? ?? =0 ?3?? 2 ·?? 2 sin ?????????????? =? ? 2?? 0 ?(? ? 2?? 0 ?? ? 2 0 ?(3?? 4 ???? )sin ?????? )???? =? ? ?? 0 ?[ 3?? 5 5 ? ? ?? 0 ?sin ?????? ]???? = 3?? 5 5 [-cos ?? ] 0 ?? ?? = 6?? ?? 5 5 7.3 Find the value of ? ?? ?(???? ×???? )·?? ???? taken over the upper portion of the surface ?? ?? +?? ?? -?? ???? +???? =?? and the boundary curve lies on the plane ?? =?? when ???? =(?? ?? +?? ?? -?? ?? )??ˆ+(?? ?? +?? ?? -?? ?? )??ˆ+(?? ?? +?? ?? -?? ?? )??ˆ (2009 : 20 Mar's) Solution: The given surface ?? 1 ?? 2 +?? 2 -2???? +???? =0 ? (?? -?? ) 2 +?? 2 =?? 2 -???? Page 3 Edurev123 7. Gauss-Divergence Theorem Stoles Theorem and Green’s to Identity 7.1 Find the work done in moving the particle on 2 round the ellipse ?? ?? ???? + ?? ?? ???? =?? ,?? = ?? under the field of force given by ???? =(?? ?? -?? +?? )??ˆ+(?? +?? -?? )??ˆ+(?? ?? -?? ?? +?? ?? )??ˆ (2009 : 20 Marks) Solution: Let ?? : ?? 2 25 + ?? 2 16 =1,?? =0 denote the ellipse. Work done =? ?? ?? ? ·?? ?? By Stoke's theorem ? ?? ?? ·?? ?? =?? ?? (?×?? )·??ˆ???? where ?? is the surface of the ellipse ?×?? = | | ??ˆ ??ˆ ??ˆ ? ??? ? ??? ? ??? 2?? -?? +?? ?? +?? -?? 3?? -2?? +4?? | | =-??ˆ-2??ˆ+2??ˆ For. Snormal is along positive z-axis ? ??ˆ =??ˆ (?×?? )·??ˆ =2 ? ?? ?? ?(?×?? )·??ˆ???? =?? ?? ?2???? =2× Area of ellipse =2?????? =2?? ·5·4 =40?? 7.2 Using divergent theorem evaluate ? ?? ????? ·?? ???? where ???? =?? ?? ??ˆ+?? ?? ??ˆ+?? ?? ??ˆ and ?? is the surface of the sphere ?? ?? +?? ?? +?? ?? =?? ?? . (2009 : 20 Marks) Solution: By gauss divergence theorem ?? ?? ??? ·?? ?? =?? ?? ?(?·?? )???? ?·?? =? ? ??? ??ˆ·?? =3?? 2 +3?? 2 +3?? 2 =3(?? 2 +?? 2 +?? 2 ) ?? is surface of sphere ?? 2 +?? 2 +?? 2 =?? 2 . ??? is the volume compressing the whole sphere. ?? ?? ??? ·?? ?? =?? ?? ?(?·?? )???? =? 1(3(?? 2 +?? 2 +?? 2 )???? Converting to spherical polar coordinates. ?? 2 +?? 2 +?? 2 =?? 2 ???? =?? 2 sin ?????????????? ?? =? ? 2?? ?? =0 ?? ? 2?? ?? =0 ?? ? ?? ?? =0 ?3?? 2 ·?? 2 sin ?????????????? =? ? 2?? 0 ?(? ? 2?? 0 ?? ? 2 0 ?(3?? 4 ???? )sin ?????? )???? =? ? ?? 0 ?[ 3?? 5 5 ? ? ?? 0 ?sin ?????? ]???? = 3?? 5 5 [-cos ?? ] 0 ?? ?? = 6?? ?? 5 5 7.3 Find the value of ? ?? ?(???? ×???? )·?? ???? taken over the upper portion of the surface ?? ?? +?? ?? -?? ???? +???? =?? and the boundary curve lies on the plane ?? =?? when ???? =(?? ?? +?? ?? -?? ?? )??ˆ+(?? ?? +?? ?? -?? ?? )??ˆ+(?? ?? +?? ?? -?? ?? )??ˆ (2009 : 20 Mar's) Solution: The given surface ?? 1 ?? 2 +?? 2 -2???? +???? =0 ? (?? -?? ) 2 +?? 2 =?? 2 -???? is of an inverted paraboloid as there is maximum value of zmax=a. Assumption ?? = +???? . Had ' ?? ' been-ve, it would not be inverted paraboloid. Consider the part of the paraboloid enclosed by ?? 1 and ?? 2 i.e., the circle of intersection in the XY-plane. ?? 2 (?? -?? ) 2 +?? 2 =?? 2 ,?? =0 These surfaces enclosed a volume. Using gauss divergence theorem ? ? ?? =?? 1 +?? 2 ?(?×?? )·?? ?? =?? ?? ??·(?×?? )???? =0 as ?·(?×?? )=0 ? ? ?? 1 ?(?×?? )·???? =-? ?? 2 ?(?×?? )·???? Now for ?? 2 ??ˆ = -??ˆ (outward normal is towards downward direction). ?×?? = | | ??ˆ ??ˆ ??ˆ ? ??? ? ??? ? ??? ?? 2 +?? 2 -?? 2 ?? 2 +?? 2 -?? 2 ?? 2 +?? 2 -?? 2 | | =(2?? -2?? )??ˆ+2(?? -?? )??ˆ+2(?? -?? )??ˆ ? (?×?? )·??ˆ =2(?? -?? ) ?? =-? ? ?? 2 ?2(?? -?? )???? =? 2(?? -?? )???? Page 4 Edurev123 7. Gauss-Divergence Theorem Stoles Theorem and Green’s to Identity 7.1 Find the work done in moving the particle on 2 round the ellipse ?? ?? ???? + ?? ?? ???? =?? ,?? = ?? under the field of force given by ???? =(?? ?? -?? +?? )??ˆ+(?? +?? -?? )??ˆ+(?? ?? -?? ?? +?? ?? )??ˆ (2009 : 20 Marks) Solution: Let ?? : ?? 2 25 + ?? 2 16 =1,?? =0 denote the ellipse. Work done =? ?? ?? ? ·?? ?? By Stoke's theorem ? ?? ?? ·?? ?? =?? ?? (?×?? )·??ˆ???? where ?? is the surface of the ellipse ?×?? = | | ??ˆ ??ˆ ??ˆ ? ??? ? ??? ? ??? 2?? -?? +?? ?? +?? -?? 3?? -2?? +4?? | | =-??ˆ-2??ˆ+2??ˆ For. Snormal is along positive z-axis ? ??ˆ =??ˆ (?×?? )·??ˆ =2 ? ?? ?? ?(?×?? )·??ˆ???? =?? ?? ?2???? =2× Area of ellipse =2?????? =2?? ·5·4 =40?? 7.2 Using divergent theorem evaluate ? ?? ????? ·?? ???? where ???? =?? ?? ??ˆ+?? ?? ??ˆ+?? ?? ??ˆ and ?? is the surface of the sphere ?? ?? +?? ?? +?? ?? =?? ?? . (2009 : 20 Marks) Solution: By gauss divergence theorem ?? ?? ??? ·?? ?? =?? ?? ?(?·?? )???? ?·?? =? ? ??? ??ˆ·?? =3?? 2 +3?? 2 +3?? 2 =3(?? 2 +?? 2 +?? 2 ) ?? is surface of sphere ?? 2 +?? 2 +?? 2 =?? 2 . ??? is the volume compressing the whole sphere. ?? ?? ??? ·?? ?? =?? ?? ?(?·?? )???? =? 1(3(?? 2 +?? 2 +?? 2 )???? Converting to spherical polar coordinates. ?? 2 +?? 2 +?? 2 =?? 2 ???? =?? 2 sin ?????????????? ?? =? ? 2?? ?? =0 ?? ? 2?? ?? =0 ?? ? ?? ?? =0 ?3?? 2 ·?? 2 sin ?????????????? =? ? 2?? 0 ?(? ? 2?? 0 ?? ? 2 0 ?(3?? 4 ???? )sin ?????? )???? =? ? ?? 0 ?[ 3?? 5 5 ? ? ?? 0 ?sin ?????? ]???? = 3?? 5 5 [-cos ?? ] 0 ?? ?? = 6?? ?? 5 5 7.3 Find the value of ? ?? ?(???? ×???? )·?? ???? taken over the upper portion of the surface ?? ?? +?? ?? -?? ???? +???? =?? and the boundary curve lies on the plane ?? =?? when ???? =(?? ?? +?? ?? -?? ?? )??ˆ+(?? ?? +?? ?? -?? ?? )??ˆ+(?? ?? +?? ?? -?? ?? )??ˆ (2009 : 20 Mar's) Solution: The given surface ?? 1 ?? 2 +?? 2 -2???? +???? =0 ? (?? -?? ) 2 +?? 2 =?? 2 -???? is of an inverted paraboloid as there is maximum value of zmax=a. Assumption ?? = +???? . Had ' ?? ' been-ve, it would not be inverted paraboloid. Consider the part of the paraboloid enclosed by ?? 1 and ?? 2 i.e., the circle of intersection in the XY-plane. ?? 2 (?? -?? ) 2 +?? 2 =?? 2 ,?? =0 These surfaces enclosed a volume. Using gauss divergence theorem ? ? ?? =?? 1 +?? 2 ?(?×?? )·?? ?? =?? ?? ??·(?×?? )???? =0 as ?·(?×?? )=0 ? ? ?? 1 ?(?×?? )·???? =-? ?? 2 ?(?×?? )·???? Now for ?? 2 ??ˆ = -??ˆ (outward normal is towards downward direction). ?×?? = | | ??ˆ ??ˆ ??ˆ ? ??? ? ??? ? ??? ?? 2 +?? 2 -?? 2 ?? 2 +?? 2 -?? 2 ?? 2 +?? 2 -?? 2 | | =(2?? -2?? )??ˆ+2(?? -?? )??ˆ+2(?? -?? )??ˆ ? (?×?? )·??ˆ =2(?? -?? ) ?? =-? ? ?? 2 ?2(?? -?? )???? =? 2(?? -?? )???? Converting to polar coordinates. ?? =?? +?? cos ?? ?? =?? sin ?? ???? =?????????? ?? =2? ? 2?? ?? =0 ?? ? ?? ?? =0 ?(?? +?? cos ?? -?? sin ?? )?????????? =2? ? 2?? ?? =0 ?[ ?? ?? 2 2 + ?? 3 3 (cos ?? -sin ?? )] 0 ?? ???? =2? ? 2?? ?? =0 ? ?? 3 2 + ?? 3 3 (cos ?? -sin ?? )???? =2· ?? 3 2 ·2?? (as integral of sin ?? and cos ?? over 0 to 2?? is zero). =2?? ?? 3 7.4 Verify Green's Theorem for ?? -?? ?????? ?????? +?? -?? ?????? ?????? the path of integration being the boundary of the square whose vertices are (?? ,?? ),( ?? ?? ,?? ),( ?? ?? , ?? ?? ) and (?? , ?? ?? ) . (2010: 20 marks) Solution: By Green's Theorem, ? (?????? +?????? )=? ( ??? ??? - ??? ??? )???????? Given equation is ?? -?? sin ?????? +?? -?? cos ?????? Here, Page 5 Edurev123 7. Gauss-Divergence Theorem Stoles Theorem and Green’s to Identity 7.1 Find the work done in moving the particle on 2 round the ellipse ?? ?? ???? + ?? ?? ???? =?? ,?? = ?? under the field of force given by ???? =(?? ?? -?? +?? )??ˆ+(?? +?? -?? )??ˆ+(?? ?? -?? ?? +?? ?? )??ˆ (2009 : 20 Marks) Solution: Let ?? : ?? 2 25 + ?? 2 16 =1,?? =0 denote the ellipse. Work done =? ?? ?? ? ·?? ?? By Stoke's theorem ? ?? ?? ·?? ?? =?? ?? (?×?? )·??ˆ???? where ?? is the surface of the ellipse ?×?? = | | ??ˆ ??ˆ ??ˆ ? ??? ? ??? ? ??? 2?? -?? +?? ?? +?? -?? 3?? -2?? +4?? | | =-??ˆ-2??ˆ+2??ˆ For. Snormal is along positive z-axis ? ??ˆ =??ˆ (?×?? )·??ˆ =2 ? ?? ?? ?(?×?? )·??ˆ???? =?? ?? ?2???? =2× Area of ellipse =2?????? =2?? ·5·4 =40?? 7.2 Using divergent theorem evaluate ? ?? ????? ·?? ???? where ???? =?? ?? ??ˆ+?? ?? ??ˆ+?? ?? ??ˆ and ?? is the surface of the sphere ?? ?? +?? ?? +?? ?? =?? ?? . (2009 : 20 Marks) Solution: By gauss divergence theorem ?? ?? ??? ·?? ?? =?? ?? ?(?·?? )???? ?·?? =? ? ??? ??ˆ·?? =3?? 2 +3?? 2 +3?? 2 =3(?? 2 +?? 2 +?? 2 ) ?? is surface of sphere ?? 2 +?? 2 +?? 2 =?? 2 . ??? is the volume compressing the whole sphere. ?? ?? ??? ·?? ?? =?? ?? ?(?·?? )???? =? 1(3(?? 2 +?? 2 +?? 2 )???? Converting to spherical polar coordinates. ?? 2 +?? 2 +?? 2 =?? 2 ???? =?? 2 sin ?????????????? ?? =? ? 2?? ?? =0 ?? ? 2?? ?? =0 ?? ? ?? ?? =0 ?3?? 2 ·?? 2 sin ?????????????? =? ? 2?? 0 ?(? ? 2?? 0 ?? ? 2 0 ?(3?? 4 ???? )sin ?????? )???? =? ? ?? 0 ?[ 3?? 5 5 ? ? ?? 0 ?sin ?????? ]???? = 3?? 5 5 [-cos ?? ] 0 ?? ?? = 6?? ?? 5 5 7.3 Find the value of ? ?? ?(???? ×???? )·?? ???? taken over the upper portion of the surface ?? ?? +?? ?? -?? ???? +???? =?? and the boundary curve lies on the plane ?? =?? when ???? =(?? ?? +?? ?? -?? ?? )??ˆ+(?? ?? +?? ?? -?? ?? )??ˆ+(?? ?? +?? ?? -?? ?? )??ˆ (2009 : 20 Mar's) Solution: The given surface ?? 1 ?? 2 +?? 2 -2???? +???? =0 ? (?? -?? ) 2 +?? 2 =?? 2 -???? is of an inverted paraboloid as there is maximum value of zmax=a. Assumption ?? = +???? . Had ' ?? ' been-ve, it would not be inverted paraboloid. Consider the part of the paraboloid enclosed by ?? 1 and ?? 2 i.e., the circle of intersection in the XY-plane. ?? 2 (?? -?? ) 2 +?? 2 =?? 2 ,?? =0 These surfaces enclosed a volume. Using gauss divergence theorem ? ? ?? =?? 1 +?? 2 ?(?×?? )·?? ?? =?? ?? ??·(?×?? )???? =0 as ?·(?×?? )=0 ? ? ?? 1 ?(?×?? )·???? =-? ?? 2 ?(?×?? )·???? Now for ?? 2 ??ˆ = -??ˆ (outward normal is towards downward direction). ?×?? = | | ??ˆ ??ˆ ??ˆ ? ??? ? ??? ? ??? ?? 2 +?? 2 -?? 2 ?? 2 +?? 2 -?? 2 ?? 2 +?? 2 -?? 2 | | =(2?? -2?? )??ˆ+2(?? -?? )??ˆ+2(?? -?? )??ˆ ? (?×?? )·??ˆ =2(?? -?? ) ?? =-? ? ?? 2 ?2(?? -?? )???? =? 2(?? -?? )???? Converting to polar coordinates. ?? =?? +?? cos ?? ?? =?? sin ?? ???? =?????????? ?? =2? ? 2?? ?? =0 ?? ? ?? ?? =0 ?(?? +?? cos ?? -?? sin ?? )?????????? =2? ? 2?? ?? =0 ?[ ?? ?? 2 2 + ?? 3 3 (cos ?? -sin ?? )] 0 ?? ???? =2? ? 2?? ?? =0 ? ?? 3 2 + ?? 3 3 (cos ?? -sin ?? )???? =2· ?? 3 2 ·2?? (as integral of sin ?? and cos ?? over 0 to 2?? is zero). =2?? ?? 3 7.4 Verify Green's Theorem for ?? -?? ?????? ?????? +?? -?? ?????? ?????? the path of integration being the boundary of the square whose vertices are (?? ,?? ),( ?? ?? ,?? ),( ?? ?? , ?? ?? ) and (?? , ?? ?? ) . (2010: 20 marks) Solution: By Green's Theorem, ? (?????? +?????? )=? ( ??? ??? - ??? ??? )???????? Given equation is ?? -?? sin ?????? +?? -?? cos ?????? Here, ?? =?? -?? sin ?? ?? =?? -?? cos ?? ? ?(?? -?? sin ?????? +?? -?? cos ?????? )=?( ??? -?? cos ?? ??? - ??? -?? sin ?? ??? )???????? (By Green's Theorem) R.H.S. : ?( ??? -?? cos ?? ??? - ??? -?? sin ?? ??? )???????? =? (-?? -?? cos ?? -?? -?? cos ?? )???? ?? ' ?? =-2? ? ?? /2 ?? =0 ?? ? ?? /2 ?? =0 ??? -?? cos ?????????? =-2[ ?? -?? -1 ] 0 ?? /2 [sin ?? ] 0 ?? /2 = +2 +1 (?? -?? /2 -1)(1-0)=2(?? -?? /2 -1) L.H.S. : ??? -?? sin ?????? +?? -?? cos ?????? In figure, from ?? to ?? : ? (?? -?? sin ?????? +?? -?? cos ?????? ) =? 0???? +0=0 as sin ?? =0 ?????? ???? =0 from ?? to ?? : ? (?? -?? sin ?????? +?? -?? cos ?????? ) =0+? ? ?? /2 ?? =0 ??? -?? /2 cos?????? (???? =0;?? = ?? 2 ) =?? -?? /2 [sin ?? ] 0 ?? /2 =?? -?? /2 from ?? to ?? : ? (?? -?? sin ?????? +?? -?? cos ?????? ) =? ? 0 ?? = ?? 2 ??? -?? ???? =-[?? -?? ] ?? /2 0 =-[1-?? -?? /2 ]=?? -?? /2 -1 from ?? to ?? : ? (?? -?? sin ?????? +?? -?? cos ?????? )=0+? ?? -?? cos ?????? =? ? 0 ?? = ?? 2 ?cos?? ???? =[sin?? ] ?? /2 0 =0-1=-1 Line integral along ?? ??? ??? ??? ??? ???? 0+?? -?? /2 +?? -?? /2 -1-1Read More
387 videos|203 docs
|
1. What is the Gauss-Divergence Theorem? |
2. Can you explain Stoles Theorem? |
3. How is Green's Identity used in mathematics? |
4. What are the practical applications of the Gauss-Divergence Theorem? |
5. How can one apply Stokes' Theorem in real-life situations? |
|
Explore Courses for UPSC exam
|