Module 8 Theory for trials AND a bit of mod 7 Flashcards
What is the order in which the model of the atom was invented? (List all the models and the names)
John Dalton, J.J Thompson, Ernest Rutherford, Niel Bohr and Schrodinger
What did John Dalton state about the nature of the atom?
John Dalton stated that atoms are indivisible and cannot be simplified.
What is a discharge tube? What is the purpose/ what does it do?
A discharge tube has very low air pressure. It is essentially a vacuum tube. it shoots electrons from the cathode to the anode. The purpose of discharge tubes was to prove what atoms were made of, as high voltage applied to low pressure air would cause rays of light to travel from the cathode to the anode.
What is an anode?
A positively charged metal
When electrons or cathode rays collide with atoms or molecules there are three outcomes. What are the three outcomes?
- Low energy collision (electron is deflected, as it interacts with air molecules and thus bounce elsewhere)
- High energy collision (some of the kinetic energy the electrons acquired as a result of the high potential difference is converted into light energy)
- Very high eenryg collision - The electron ionises the atom or molecule resulting in an ion and extra free electron.
What was the cathode ray assumption?
Scientists wondered whether cathode rays were made of charged particles or was a type of radiation. In short, they wondered whether the electron was a particle or a wave. (Waves as in similar to UV light)
What was the maltese cross experiment? Who made the experiment?
Julius Plucker. The maltese cross experient was an experiment which shined light through a cross, creating a shadow cross. By observing the shadow, they found out that the shape is the same as the original cross, which meant scientists concluced that the cathode rays travelled in straight lines.
What is the paddle wheel experiment? Who amde it?
The paddle wheel experiment consisted of a paddle wheel inside a discharge tube. The paddle wheel rotated when the light/cathode ray travelled through it. The paddle wheel experiment helped conclude that cathode rays had momnetum and therefore mass. In short, the paddle wheel experiment concluded that cathode rays were made of electrons, since waves do NOT have mass.
Cathode rays are charged and undergo deflection perpendicular to an appleid magnetic field. True or False.
True
What is the JJ Thompson experiment? (The charge to mass exepriment)
The JJ Thompson experiment was a model which helped prove that cathode rays consisted of electrons. Esentially, Thomson balanced the force of electric and magnetic fields using a cathode ray tube, such that the magnetic force (centripetal force was equal to the electric force.
Therefore qvB = mv^2 / r
Also, qvB = qe (the v is velocity for both)
Therefore V = E/B
In short, JJ Thompson proved the existence of electrons
What is the direction of the magnetic force?
Since the magnetic force always acts perpendicularly to the charged particle’s velocity, it supplies a centripetal force. The particle is thus brought into uniform circular motion.
Is the force of a magnetic field centripetal?
Yes, because using the right hand palm rule, it will undergo circular motion since the magnetic force is always perpendicular to the charged particle’s velocity.
Therefore what is the concluding formula for the JJ Thompson’s experiment?
q / m = E / (B^2 x r)
What are the three main factors which the deflection of a particle depends on?
- Magnitude of negative charge
- Mass of Particle
- The strength of electric and magnetic fields
Charge to mass ratio is 1.76 x 10^11 Coulombs per Kg
What is Milikan’s oil drop experiment?
Milikan’s oil drop experiment was to measure the charge of an electron by suspending it to a ceiling such that it falls down due to gravity but is pushed upwards due to the electric field.
