(Electron travelling though two horizontal plates) In the diagram P1 and P2 are
ID: 1411298 • Letter: #
Question
(Electron travelling though two horizontal plates)
In the diagram P1 and P2 are two parallel horizontal plates that are 8.9 mm apart in a vacuum and have a potential difference of 158 volts maintained between them, the upper plate being positive. Also, there is a horizontal magnetic field of 0.043 as shown.
A horizontal beam of electrons is directed between the plates so that it is moving at right angles to the magnetic field as shown.
a) What is the magnitude of the electric field between the plates?
b) What is the magnitude of the force due to the electric field acting on each electron?
c) What is the direction of the magnetic force acting on the electron?
d) What is the speed of an electron that will allow it to pass undeflected between the plates? (Neglect the effect of gravity.)
electron beam- xxxxxx 2 x x x x x x xExplanation / Answer
V = 158 v
d = 8.9 mm
(a)
magnitude of the electric field between the plates , E = V/d
E = 158 / (8.9 * 10^-3)
E = 17752.8 V/m
(b)
Force due to Electric Field, F = q*E
F = 1.6 * 10^-19 * 17752.8 N
F = 2.84 * 10^-16 N
(c)
As Magnetic Field is into the page & Electron is moving to the right !!
Direction of Magnetic Force = Downwards or to the South !!
(d)
For electron to pass undeflected between the plates,
Magnetic Force = Electric Force
q*v*B = q*E
v*0.043 = 17752.8
v = 4.13 * 10^5 m/s
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