![]() To test this idea, he took great pains to extract nearly all of the gas from a tube, and found that now the cathode rays did bend in an electric field after all. Thomson suspected that the traces of gas remaining in the tube were being turned into an electrical conductor by the cathode rays themselves. A charged particle will normally curve as it moves through an electric field, but not if it is surrounded by a conductor (a sheath of copper, for example). Ll attempts had failed when physicists tried to bend cathode rays with an electric field. As Thomson saw it, the negative charge and the cathode rays must somehow be stuck together: you cannot separate the charge from the rays. The electrometer did not register much electric charge if the rays were bent so they would not enter the slit. He found that when the rays entered the slit in the cylinders, the electrometer measured a large amount of negative charge. Thomson wanted to see if, by bending the rays with a magnet, he could separate the charge from the rays. Perrin had found that cathode rays deposited an electric charge. These cylinders were in turnĬonnected to an electrometer, a device for catching and measuring electrical charge. Irst, in a variation of an 1895 experiment by Jean Perrin, Thomson built a cathode ray tube ending in a pair of metal cylinders with a slit in them. He advanced the idea that cathode rays are really streams of very small pieces of atoms. Thomson found that this value comes to \( 1.76 \times 10^8 C/g \).O atoms have parts? J.J. The charge-to-mass ratio of the electron can be determined by measuring the effects of the magnetic and electric fields on the motion of the beam.What is the charge-to-mass ratio for the cathode ray particles?.If the correct combination is reached, the can completely cancel each other out and not deflect the rays at all. When both electric and magnetic forces are applied to the cathode ray, they combine against or with each other to deflect the cathode rays.What is the effect of simultaneous electric and magnetic fields on the cathode ray?. ![]() ![]() Again, this is due to the negative charge the cathode rays possess. When the north pole is facing towards the CTR, the beam is deflected upwards. If the south pole is facing towards the CTR (Cathode Ray Tube), the beam is deflected down. When a magnetic field is applied, the cathode rays get deflected.What is the effect of a magnetic field on the cathode ray?.This is because the cathode rays are negatively charged. When an electric field is applied to a stream of cathode rays, they are deflected towards the positive plate.What is the effect of an electric field on the cathode ray?.Notice the dotted circle indicating the position of the coils, the direction of the magnetic field between the coils and the value of the field. In the Thomson applet, set the voltage at 0 V and move the slider for the current to the right. When a current flows through the coils, a uniform magnetic field is created in the region between the horizontal plates. Using the same tube as shown in Figure 1 (above), he placed a pair of coils outside of the tube and on either side of the horizontal plates (Figure 3, below). Thomson also used a magnetic field to affect the beam of cathode rays. In the Thomson applet, this angle is provided by selecting Deflection Angle in the Options menu. From measurements of this deflection, he was able to calculate the angle of deflection. Thomson measured the deflection of the beam using a ruler etched on the end of the tube. You can see a simulation of this glow on the far right of the applet diagram, as shown in Figure 2. In Thomson’s experiment, a fluorescent material was coated on the end of the tube to produce a glowing dot where the cathode rays hit.
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