Tricky questions

## Electric Charges And Fields

- Some questions are often misinterpreted by the students. Let's explore them!
1
Electron motion in electric field
When you project an electron perpendicular to the uniform electric field then electron will experience force, the direction of force will be opposite of direction of electric field. Because the direction of force is constant and perpendicular to initial velocity, velocity will continuously change. Try this question and predict the path of electron.
An electron is moving with constant velocity along -axis. If a uniform electric field is applied along -axis, then its path in the  plane will be :
A
a straight line
B
a circle
C
a parabola
D
an ellipse
2
Flux linked with cube or cube faces when charge placed at any corner
Electric flux lines comes symmetrically from the point charge. When you keep it at a corner of cube then only few percentage of flux will enter in cube. In this case flux linked the face/cube can be calculated by assuming another similar cubes, that are arranged in such away that this charge is at center of bigger cube. Let's solve this question
A charge is kept at the corner of a cube. Electric flux passing through one of those faces not touches that charge is:-
A
B
C
D
3
Concentric metallic shell
Whenever you give charge on metallic shell then all charges will appear at its upper surface. It means that sum of charge available inside would be zero. Apply this concept and solve below question.
Three concentric metallic spherical shells of radii , are given charges , respectively. It is found that the surface charge densities on the outer surfaces of the shells are equal. Then, the ratio of the charges given to the shells, , is :
A
B
C
D
4
Strength of electric field
When two charged particles of different magnitude are kept along the line then the electric field strength shows a definite patterns. Electric field at the location of charge shows infinite and at very far distance, it show zero.
Two point charges +q and +9q are placed at (-a, 0) and (+a, 0). Take electric field intensity to be positive if it is along positive x-direction. The variation of the electric field intensity as one moves along the x-axis is :
A
B
C
D
5
Electric field inside cavity of cylindrical charged body
Electric field inside cylindrical cavity of solid cylinder can be calculated by assuming two separately uniformly charged solid cylinder. If bigger cylinder have charge density then we can assume cylinder cavity have charge density . Lets solve below question.
A very long, solid insulating cylinder with radius has a cylindrical hole with radius bored along its entire length. The axis of the hole is a distance from the axis of the cylinder, where (as shown in figure). The solid material of the cylinder has a uniform has a uniform volume charge density . Find the magnitude and direction of the electric field inside the hole, and show that this is uniform over the entire hole.
6
Charge induction in dielectric sphere
When you keep a dielectric sphere inside the electric field then some amount of charge will induce at its surface. This induced charge changes electric field strength at inside or outside point.
Compare the electric field strength at different points.
A dielectric in the form of a sphere is introduced into a homogeneous electric field. and are three points as shown in Fig. Then
A
Intensity at increases while that at and decreases
B
Intensity at and decreases whereas intensity at increases
C
Intensity at and increases and that at decreases
D
Intensity at and decreases