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He used different discharge tubes fitted with electrodes of different metals.He placed different gases in the tube.

The negatively charged material particles constituting the cathode rays are called electrons.įor determination of the ratio of charge/mass of electrons This indicates that cathode ray produce heating effect.ĥ)They produce green fluorescence on the glass walls of the discharge tube as well as on certain other fluorescent substances such as zinc sulphide.Ħ)They possess penetrating effect ie they can easily pass through thin foils of metals. This shows that cathode rays carry negative charge.Ĥ)When cathode rays strike a metal foil, the latter becomes hot. This shows that cathode rays are made up of material particles.ģ)When an electric field is applied on the cathode rays, they are deflected towards the positive plate of the electric field. This shows that cathode rays travel in straight line.Ģ)If a light paddle wheel mounted on an axle is placed in their path, the wheel begins to rotate. This shows that some invisible rays are emitted from the cathode which passed through the holes of the anode and strike the wall.These rays were called as cathode rays.ġ)They produce a sharp Shadow of the solid object placed in their path. When high voltage of about 10000 volts is applied between the electrodes the following results are observed at different pressures :ġ) When the gas pressure inside is one atmosphere, no current flows between the electrodes.Ģ) When the pressure is reduced to about 10 millimetre ,the current starts flowing between the electrodes and coloured glow is observed ,the colour depending upon the nature of the gas taken.ģ) When the pressure is for the reduced to about 0.01 millimetre ,the glow between the electrodes disappear but the current continuous to flow and if a perforated anode is used, a faint greenish glow is observed on the glass walls behind the anode. Many thanks to MagLab physicist William Coniglio, the science advisor for this page, for his time and expertise.​William crookes in 1879 studied the conduction of electricity through gases at low pressure.ġ) He took a discharge tube which is a long glass tube, sealed at both the ends and fitted with two metal electrodes.Ģ) It has a side tube fitted with a stop cock which can be connected to a vacuum pump to reduce the pressure of the gas inside to any desired value. The electrons in the cathode rays would deflect toward the positively charged plates, and away from the negatively charged plates. The results showed electrostatic deflection (as opposed to the electromagnetic deflection described above).

In addition to experimenting with magnets, scientists also experimented to see what would happen if charged plates were positioned near the tube. (As you apply that rule, remember that the electrons in the cathode ray are travelling opposite the flow of conventional current.) Try flipping the magnet by checking the Flip Magnet box, and observe how the beam then deflects in the opposite direction. That rule describes how a charged particle (our electron) moving in a magnetic field will be deflected by that field at a right angle to both the field and to the direction of the particle. What happens in the tube is a consequence of the Lorentz Force, which is explained by the left hand rule. Thomson would determine that the molecules hypothesized by Crookes were actually negatively charged subatomic particles that he called corpuscles, but which were eventually named electrons. William Crookes experimented with cathode rays and magnets in a similar manner, and his observations on the deflection of the rays by magnetic fields led him to conclude that they were composed of negatively charged molecules. Observe the effect of a magnetic field on cathode rays by using the Magnet Position slider to move a horseshoe magnet (its north pole facing you) so that its poles straddle the cathode ray tube. These electrons, or cathode rays, are passed through a small opening near the cathode and then travel in a straight line toward the anode, passing through a fluorescent screen positioned between the cathodes that allows you to see the path of the electrons. A high voltage is transmitted to the cathode ray tube, inducing the cathode to emit electrons – essentially an electrical current. The tube illustrated in the tutorial contains a negative electrode ( Cathode) at one end and a positive electrode ( Anode) at the other. Scientists used special vacuum tubes, such as the Crookes tube and the cathode ray tube, to study this phenomenon.