﻿ In a discharge tube ionization of enclosed gas is produced due to collisions between | Electric Charges and Fields

## Previous Year Papers

Download Solved Question Papers Free for Offline Practice and view Solutions Online.

## Test Series

Take Zigya Full and Sectional Test Series. Time it out for real assessment and get your results instantly.

## Test Yourself

Practice and master your preparation for a specific topic or chapter. Check you scores at the end of the test.

# Electric Charges and Fields

#### Multiple Choice Questions

11.

The electric field of an electromagnetic wave in free space is given by , where t and x are in seconds and meters respectively. It can be inferred that

1) the wavelength λ is 188.4 m.
2)The wave number k is 0.33 rad/m.
3)The wave amplitude is 10 V /m.
4)The wave is propagating along +x direction

• (3) and (4)

• (1) and (2)

• (2) and (3)

• (2) and (3)

311 Views

12.

The electric potential at a point (x, y, Z) is given by

V = - x2y -xz3 + 4

The electric field E at that point is

343 Views

13.

A hollow cylinder has to charge q coloumb within it. Φ is the electric flux in a unit of voltmeter associated with the curved surface B, the flux linked with the plane surface A in a unit of voltmeter will be:

579 Views

# 14.In a discharge tube ionization of enclosed gas is produced due to collisions between positive ions and neutral atoms/molecules negative electrons and neutral atoms/molecules photons and neutral atoms/molecules photons and neutral atoms/molecules

B.

negative electrons and neutral atoms/molecules

In a discharge tube, after being accelerated though a high potential difference the ions in the gas strike the cathode with huge kinetic energy. This collision liberates electrons from the cathode. These free electrons can further liberate ions from gas molecules through collisions. The positive ions are attracted towards the cathode and negatively electrons move towards anode. Thus, ionization of gas results.

840 Views

15.

A square surface of side L m is in the plane of the paper. A uniform electric field , also in the plane of the paper, is limited only to the lower half of the square surface, (see figure). The electric flux in SI units associated with the surface is

• zero

• zero

614 Views

16.

An electron falls from rest through a vertical distance h in a uniform and vertically upward directed electric field E. The direction of electric field is now reversed, keeping its magnitude the same. A proton is allowed to fall from rest in it through the same vertical distance h. The time of fall of the electron, in comparison to the time of fall of the proton is

• Smaller

• 5 times greater

• Equal

• 10 times greater

17.

A certain charge Q is divided into two parts q and Q-q. How the charge Q and q must be related so that when q and (Q-q) is placed at a certain distance apart experience maximum electrostatic repulsion?

• Q = 2q

• q = 3q

• Q = 4q

• Q= 4q + c

18.

A charged particle 'q' is shot with speed v towards another fixed charged particle Q. It approaches Q upto the closest distance r and then returns. If q were given a speed 2v, the closest distance of approach would be

• r

• 2r

• r/2

• r/4

19.

A conducting sphere of radius R = 20 cm is given by a charge Q = 16μC. What is E at centre?

• 3.6×106 N/C

• 1.8×10N/C

• Zero

• 0.9×106 N/C

20.

If an insulated non-conducting sphere of radius R has charge density ρ. The electric field at a distance r from the centre of sphere (r > R) will be