Physics Ncert Solutions Class 12th

This is a Multiple Choice Questions as classified in NCERT Exemplar

Answer. (a)

Explanation- field lines are always perpendicular to the surface.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Answer. (a)

Explanation- when a point positive charge brought near an isolated conducting plane, some negative charge develops on the surface of the plane towards the charge and an equal positive charge develops on opposite side of the plane. By process called induction.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Answer. (c)

Explanation- As the space is increasing towards right means electric field is decreasing so as force is also decreasing . so force on -p is more than the force on +p 

This is a Multiple Choice Questions as classified in NCERT Exemplar

Answer. (b)

Explanation-The charges may be located anywhere inside the surface, if the surface      is so chosen that there are some charges inside and some outside, the electric field on the left side of equation is due to all charges, both inside and outside S.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Answer. (d) 

Explanation- Total flux inside a conducting sphere is depend upon the algeabric sum of total charge inside that surface, which is same for all fig. As it does not depend upon shape of a body

This is a Multiple Choice Questions as classified in NCERT Exemplar

Answer- (a)

Explanation- when a positive point charge is brought near an isolated conducting sphere without touching the sphere, then the free electron in the sphere are attracted towards the positive charge. This leaves an excess positive charge on right side of sphere . And also by induction the negative charge is setup across left side. So field lines first goes from positive charge (+q) to negative charge of sphere then from positive charge of sphere to negative charge anywhere in the universe.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Answer.   (a)

Explanation-The force between (q1, q2) and (q1, q3) is must be attractive to net forces act in positive direction of x . so q1 must be negative. But if we place a positive charge Q in positive direction of x then it must be attractive towards along x-axis. So it will be attractive towards positive x axis. 

This is a Short Answer Type Questions as classified in NCERT Exemplar

Explanation- (i)The cesium atoms, are situated at the corners of a cube and Cl atom is situated at the centre of the cube. From the given figure, we can analyse that the chlorine atom is at equal distance from all the eight comers of cube where cesium atoms are placed. Thus, due to symmetry the electric field due to all Cs atoms, on Cl atom will cancel out. Hence net electric field at the centre of cube is zero.

(ii) we know, f=qE  E= Kq/r²= Ke/r²

F= e (E)=e (ke/r²)=ke²/r²

Distance= $\sqrt[]{r^2+r^2+r^2}$ = $\sqrt[]{{0.2}^2+{0.2}^2+{0.2}^2}*$ 10^-9m

F=8.99 $*$ 10⁹ (1.6 $*$ 10^-16)²/ (0.346 $*$ 10^-9)²=1.92 $*$ 10^-9N