Thomson set up his cathode ray tube with, but placed a magnet above the path of the rays. He knew that electrically charged objects can be deflected by magnets (Michael Faraday discovered this and is his theory of electromagnetism). In Thomson's 1st experiment he wanted to see if he could separate the negative charge out of the rays. They knew that some sort of ray was coming from the cathode (filament) and that there was some sort of negative charge emitted from the cathode too because an electrical current flowed in the circuit between the screen and the cathode. In reality the power needs to be very high though so you would use mains electricity converted to D.C.Īt the time Thomson started his work, the glow observed on the screen was mysterious and nobody knew what it was. You then connect a second battery with the (+) terminal connected to the screen and the (-) terminal connected to the filament. (It's hard to explain how it is wired up without drawing a picture! Think of it as the filament being connected to a battery - it will glow just like a light bulb but not as brightly. This puts electrical field between the screen and the filament - and if the screen is positive then electrons from the filament will stream towards the screen causing it to glow. At the same time you connect the filament and the fluorescent screen together with an electrical source. You pass an electrical current through the filament and it starts to glow. At the other end is fluorescent screen which is just like an old fashioned TV screen. Inside at one end is an electrical filament (which is actually called the cathode in this experiment) just like the one inside a light bulb. His experiments were all conducted with what is known as a cathode ray tube, so firstly I will try to explain what this is and how it works.Ī cathode ray tube is a hollow sealed glass tube which is under vacuum (has had all the air sucked out of it).
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