Ideas to Implementation.

Essay by chao2410High School, 12th gradeB, March 2004

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Cathode Ray tubes allow a manipulation of a stream of charged particles

*CRT - consist of evacuated glass tube containing two electrodes

*High voltage is applied across electrodes - stream of negatively charged particles from cathode to anode

*Structures built around the cathode (e.g. electric plates and magnetic coils) can be used to manipulate CR

Charge particles produce an electric field

*Electric field exists in any region that an electrically charged object experiences a force

*A charge in an electric field experiences a force F = Eq

Oppositely charged parallel plates

*Electric field moves uniformly from positive to negative

*For oppositely charged plates - E = V/d

Force acting on a charge moving through a magnetic field

*Charges moving through a magnetic field produces a force

*F = qvbSin+

*Force greatest when particle is perpendicular to electrical field

Thompson's experiment to measure charge/Mass ratio

*Subjected cathode ray to deflection by know electric and magnetic fields - set at right angles to each other

*Arranged magnetic and electrical forces to balance out forces acting out of CR

*-ve particles from cathode move through a collimating anode - subject CR into thin beam

*A known magnetic field was applied, and the electrical field, once applied, was adjusted to until returned to O

Fb = Fe

qvB = qE

v = E/B - which finds velocity of particle


Fb = Fc

qvb = mv2/r

q/m = V/Br

Outline role of Cathode ray in

*Electron gun

oConsists of

"XA thermionic cathode - ejects electrodes when heated

"XA anode - collimator to subject beam to a thin stream

"XGrids to control brightness

*Electric field or deflection system

oHelps to deflect CR for various uses

oConsists of two parallel plates - one horizontal the other vertical

*Fluorescent screen

oEnd of the CRT coated with fluorescent...