NCERT Physics Class 12 Exemplar Chapter 1 Electric Charges and Fields Part 7

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Q.18 Sketch the electric field lines for a uniformly charged hollow cylinder shown in Fig.

Tittle: Image of The Uniformly Charged Hollow Cylinder

Field Lines in Cylinder

Tittle: Image of The Uniformly Charged Hollow Cylinder

Solution:

The electric field lines start from positive charges and move towards infinity and meet plane surface normally as shown in the figure below:

Tittle: Image of The Meet Plane Surface Normally

Field Lines Sections

Tittle: Image of The Meet Plane Surface Normally

Q.19 What will be the total flux through the faces of the cube (Fig.) with side of length if a charge is placed at

Flux through face

Flux through Face

Flux through face

(a) A: a corner of the cube.

(b) B: mid-point of an edge of the cube.

(c) C: centre of a face of the cube.

(d) D: mid-point of B and C.

Solution:

(a)Use of symmetry consideration may be useful in problems of flux calculation. We can imagine the charged particle is placed at the centre of a cube of side . We can observe that the charge is being shared equally by cubes. Therefore, total flux through the faces of the given cube .

Tittle: Image of The Corner of the Cube

Faces of Cube (B)

Tittle: Image of The Corner of the Cube

(b) If the charge is placed at . middle point of an edge of the cube, it is being shared equally by cubes. Therefore, total flux through the faces of the given cube .

Charge at middle point B

Charge at Middle Point B

Charge at middle point B

(c) If the charge is placed at . the centre of a face of the cube, it is being shared equally by cubes. Therefore, total flux through the faces of the given cube

Charge at point C

Charge at Point C

Charge at point C

(d) Finally, if charge is placed at . the mid-point of and , it is being shared equally by cubes. Therefore, total flux through the faces of the given cube .

Charge at point D

Charge at Point D

Charge at point D

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