I don't see the idea of the similar triangles. Are the units of the formula even correct? Looks like distance = distance cubed!! But the electrons are still deflected while between the plates and D is NOT zero. For instance, suppose L = 0 (the phosphor screen is right at the end of the deflecting plates). They get deflected (by plates or coils) after the gun, but they move at a constant speed toward the anode/faceplate after leaving the electron gun.īTW, I think you forgot to square the velocity in your equation here:ĭ = * is given in the lab In a CRT, the end of the electron gun is usually at the anode voltage, so the electrons do not accelerate the rest of the way to the anode and phosphur. So if you accelerate an electron through a voltage difference of 1kV, it has 1keV of kinetic energy. The handy thing to remember is that eV is a unit of energy. If a=qE/m and we know the q charge value for an electron, we know the mass of an electron, how do I find the E value produced by 250V? We did all kinds of stuff with kinetic energy in Newtonian physics but I'm not sure how to apply it with voltage. Having only been given the accelerating voltage (250V) I'm not sure where to begin. If we are given the accelerating voltage (250V) how would I calculate the kinetic energy of the electron as it leaves the positive end of the charge area? What is the formula for the speed of an electron along the tube (vz) as it leaves the positive charge area, in terms of the accelerating potential Va and the mass and charge of an electron. By heating the cathode, the kinetic energy of the free electrons on the metal surface of the cathode is increased, allowing the electrons to free themselves more easily from the cathode.Have a few questions on CRT's. To ensure that the electrons are extracted from the cathode at such a low voltage, the tube is equipped with an independent heating circuit linked to the cathode. When a voltage of 50 volts is applied between the anode and cathode, the electron beam becomes visible as it travels from the cathode towards the anode. For visualization purposes, the tube contains a small quantity of argon gas. Sigmatron’s Model ST-121 is made of glass and has been pressure-sealed to create a near-perfect vacuum. To meet the requirements of High School Physics programs, a cathode ray tube must help determine the orientation and direction of cathode rays, the effect of a magnetic field on cathode rays and the effect of an electrostatic field on cathode rays. Furthermore, since the electrons that constitute the ray are accelerated by a voltage of only 350 V, there is no risk of X-ray emission. To meet these requirements, Sigmatron offers a cathode ray tube that does not contain a metallic barrier in the electron trajectory. To eliminate the possibility of X-ray emissions, one has to reduce the acceleration of the electrons that constitute the ray and make sure that they do not hit a metallic barrier during their trajectory. As a general rule, when accelerated electrons (cathode rays) suddenly decelerate when they come into contact with a metallic surface, X-rays are produced. In order to comply with Health Canada requirements, a cathode ray tube must not emit a harmful amount of X-rays (< 0.5 mR/h - milliroentgen per hour). Model ST-121 is also equipped with two horizontal deflection plates used to demonstrate the effect of an electrostatic field on cathode rays. Sigmatron’s Cathode Ray Tube Model ST-121 allows students to discover the properties of cathode rays in new and exciting ways! They can determine the orientation and direction of cathode rays or demonstrate the effect of a magnetic field on cathode rays.
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