# Physics Questions

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

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