Q1.Two plane metal plates 4.0 cm long are held horizontally 3.0 cm apart in a

vacuum, one being vertically above the other. The upper plate is at a potential of

300 volts and the lower is earthed Electrons having a velocity of 10 x 10^7 m s~ 1

are injected horizontally midway between the plates and in a direction parallel

to the 40 cm edge. Calculate the vertical deflection of the electron beam as it

emerges from the plates, (e/m for electron = 1.8 x 10^11 Coulomb/kg.) (N.)

Q2. If the path of the electron is a circle, prove that the time for a complete revolution

is independent of the speed of the electron.

In the ionosphere electrons execute 1.4 x 10^6 revolutions in a second. Find the

strength of the magnetic induction B in this region. (Mass of an electron = 9.1 x

10-31Kg; electronic charge = l.6 x 10^-19 coulomb.) (C.)

Q3. Describe and give the theory of a method to determine e the electronic charge.

Why is it considered that all electric charges are multiples of e ?

An electron having 450 electron-volts of energy moves at right angles to a

uniform magnetic field of magnetic induction (flux density) 1.50 x 10^-3 webermetre^-2 .

Show that the path of the electron is a circle and find its radius. Assume

that the specific charge of the electron is 1.76 x 10^11 coulomb/kg. (L.)

Q4. Describe a method for measuring the charge per unit mass for the electron,

showing how the value is calculated from the observations.

An ion, for which the charge per unit mass is 4.40 x 10^7 C/kg has a velocity

of 3.52 x 10^7 cm/s and moves in a circular orbit in a magnetic field of induction

0.4T.What will be the radius of this orbit? (L.)

Q5. An electron with a velocity of 10 7 ms-2 enters a region of uniform magnetic

flux density of 010T, the angle between the direction of the field and the

initial path of the electron being 25°. By resolving the velocity of the electron

find the axial distance between two turns of the helical path. Assume that the

motion occurs in a vacuum and illustrate the path with a diagram, (e/m =

1.8 x 10^11 coulomb/kg.)

Source:Advanced Level Physics 5th Edition by Nelkon & Parkar

Physics Questions from Nature of Particles