Thomson's Experiment Quiz
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Questions and Answers

What happens to the electrons when the electric field is turned off?

  • They will continue to accelerate upwards.
  • They stop moving completely.
  • They change direction and travel horizontally.
  • They are influenced solely by the magnetic field. (correct)

    • What force is primarily responsible for the centripetal motion of electrons in Thomson's experiment?

  • Electric force
  • Magnetic force (correct)
  • Gravitational force
  • Frictional force

    • In Thomson's experiment, if the magnetic field covered a larger area, what effect would this have on the electrons?

  • Their velocity would decrease.
  • They would be trapped and move in a larger circle. (correct)
  • They would be forced to move in a straight line.
  • They would not be affected at all.

    • What is the relationship between the charge, mass, velocity, magnetic field, and radius in Thomson's formula?

    <p>The radius is inversely proportional to the magnetic field strength.</p> Signup and view all the answers

    Which of the following values is given for the magnetic field in the example provided?

    <p>5.80e-4 T</p> Signup and view all the answers

    What is implied about the velocity of electrons in Thomson's experiment with high velocities?

    <p>High velocities significantly impact the final calculations.</p> Signup and view all the answers

    Which variable represents the charge-to-mass ratio in Thomson's formulas?

    <p>q</p> Signup and view all the answers

    What could Thomson do if he wished to increase the stability of the electron path?

    <p>Increase the magnetic field strength.</p> Signup and view all the answers

    What is the initial purpose of the hot filament in the experiment?

    <p>To eject electrons</p> Signup and view all the answers

    What effect does the electric field have on electrons when only the second set of parallel plates is activated?

    <p>Electrons move upwards</p> Signup and view all the answers

    In the presence of a magnetic field alone, how do the electrons behave?

    <p>They move downwards</p> Signup and view all the answers

    What results when both the electric and magnetic fields are activated correctly?

    <p>Electrons travel in a straight line</p> Signup and view all the answers

    What would happen if the voltages applied to the plates were equal and opposite?

    <p>Electrons would not be affected</p> Signup and view all the answers

    How does the design of the CRT ensure the electrons follow a controlled path?

    <p>By manipulating the strength of the electric and magnetic fields</p> Signup and view all the answers

    What phenomenon occurs when electrons hit the globe at the end of the tube due to the electric field?

    <p>They create a glow</p> Signup and view all the answers

    Which of these statements is true regarding the movement of electrons in a CRT?

    <p>Both electric and magnetic fields can affect the electrons' trajectory</p> Signup and view all the answers

    What significant outcome did J.J. Thomson achieve in his first experiment?

    <p>He proved that cathode rays are made of negative charges.</p> Signup and view all the answers

    What did Thomson use to improve the accuracy of his experiments in the cathode ray tube?

    <p>A vacuum tube</p> Signup and view all the answers

    In Thomson's second experiment, what did he observe about the cathode rays in an electric field?

    <p>They deflected in the direction expected for negative charges.</p> Signup and view all the answers

    What key property did Thomson measure in his third experiment?

    <p>The charge-to-mass ratio of the cathode rays</p> Signup and view all the answers

    Why was the charge-to-mass ratio important in Thomson's research?

    <p>It was the first measurement into atomic structure.</p> Signup and view all the answers

    What was the main purpose of John Dalton's Solid Sphere Model?

    <p>To explain the chemistry he was studying.</p> Signup and view all the answers

    What were cathode rays observed to do in a cathode ray tube?

    <p>Cause a glow at the positive end of the tube.</p> Signup and view all the answers

    Which of the following statements about Thomson's experiments is FALSE?

    <p>Thomson first identified the charge of cathode rays.</p> Signup and view all the answers

    Who among Thomson's associates also won a Nobel Prize in Physics?

    <p>Ernest Rutherford</p> Signup and view all the answers

    What did William Crookes conclude about the particles in a cathode ray tube?

    <p>They were negatively charged.</p> Signup and view all the answers

    Why is it called a cathode ray tube?

    <p>Because the negative electrode is referred to as the cathode.</p> Signup and view all the answers

    What did Thomson infer about the nature of cathode rays after conducting his experiments?

    <p>They consist of negatively charged particles.</p> Signup and view all the answers

    Which of the following best describes Dalton's view on atoms?

    <p>They were solid pieces of matter that could not be subdivided.</p> Signup and view all the answers

    What notable effect did Jean Baptiste Perrin demonstrate with cathode rays?

    <p>They caused metals to gain a negative charge.</p> Signup and view all the answers

    What limitation did Dalton's model of atoms have?

    <p>It could not explain how atoms bond chemically.</p> Signup and view all the answers

    What was one of the first experiments that provided insight into atomic structure?

    <p>Observing the glowing effect of cathode rays.</p> Signup and view all the answers

    What is the relationship between electric force and magnetic force when they are balanced?

    <p>Electric force and magnetic force are equal in magnitude.</p> Signup and view all the answers

    In the velocity selector formula, what does the variable 'E' represent?

    <p>Electric field measured in Newtons per Coulomb or Volts per meter.</p> Signup and view all the answers

    If the electric field is 7.62e7 N/C and the magnetic field is 3.65 T, what is the velocity of the electrons?

    <p>2.09e7 m/s</p> Signup and view all the answers

    How can the velocity of electrons be adjusted in a CRT setup?

    <p>By adjusting the electric and magnetic fields.</p> Signup and view all the answers

    What is the physical significance of the computed electron velocity being almost 10% the speed of light?

    <p>Indicates a high-energy process.</p> Signup and view all the answers

    What does the variable 'v' represent in the equation $E = vB$?

    <p>Velocity of electrons in meters per second.</p> Signup and view all the answers

    What happens to the forces acting on electrons when they are at the specific velocity defined by the velocity selector formula?

    <p>Electric and magnetic forces become equal and opposite.</p> Signup and view all the answers

    What defines the velocity range of electrons in a velocity selector?

    <p>The electric and magnetic fields used.</p> Signup and view all the answers

    What aspect of cathode rays did Thomson's findings highlight?

    <p>They were super concentrated charge.</p> Signup and view all the answers

    What nickname is commonly used for Thomson's model of the atom?

    <p>Plum Pudding Model</p> Signup and view all the answers

    What was Thomson's initial belief about the composition of atoms?

    <p>Atoms are made entirely of electrons.</p> Signup and view all the answers

    How did Thomson explain the presence of neutral atoms?

    <p>They must have positive substances to cancel electrons.</p> Signup and view all the answers

    What can be inferred about Thomson's value for the charge-to-mass ratio?

    <p>It was thousands of times larger than previously measured.</p> Signup and view all the answers

    What did Thomson's conclusion about electrons suggest about their size?

    <p>Electrons must be extremely tiny and densely charged.</p> Signup and view all the answers

    What physical analogy is used to describe Thomson's Plum Pudding Model?

    <p>A lump of stuff with pieces floating inside.</p> Signup and view all the answers

    What experimental evidence contributed to Thomson's conclusions about cathode rays?

    <p>Cathode rays could pass through metal foil.</p> Signup and view all the answers

    What was the main limitation of Dalton's Solid Sphere Model?

    <p>It could not explain chemical bonding.</p> Signup and view all the answers

    What effect did William Crookes observe in his cathode ray tube experiments?

    <p>Cathode rays caused the tube to glow.</p> Signup and view all the answers

    What did Jean Baptiste Perrin demonstrate about cathode rays in his experiments?

    <p>They gained a negative charge when shot into a metal tube.</p> Signup and view all the answers

    How did cathode ray tubes contribute to the understanding of atomic structure?

    <p>They showed that electrons were part of atoms.</p> Signup and view all the answers

    What aspect of cathode rays was significant to J.J. Thomson's research?

    <p>Their integration with magnetic fields.</p> Signup and view all the answers

    Which statement best reflects the characteristics of atoms according to Dalton's model?

    <p>Atoms are solid, indivisible particles.</p> Signup and view all the answers

    What concept did Thomson's Plum Pudding Model introduce about the atom?

    <p>Atoms are positively charged spheres with embedded electrons.</p> Signup and view all the answers

    What approach did Crookes use to investigate cathode rays?

    <p>Implementing high-quality vacuum tubes.</p> Signup and view all the answers

    What occurs to the electrons in the absence of the electric field?

    <p>They accelerate downward due to the magnetic field.</p> Signup and view all the answers

    In Thomson's experiment, what is the effect of increasing the size of the magnetic field?

    <p>Electrons will be trapped and follow a circular path.</p> Signup and view all the answers

    Which equation represents the relationship between the charge-to-mass ratio and the other variables in Thomson's findings?

    <p>$q v = m Br$</p> Signup and view all the answers

    What does the variable 'r' signify in Thomson's equations?

    <p>The radius of the electron's path.</p> Signup and view all the answers

    What role does the magnetic field play in the movement of electrons in Thomson's experiment?

    <p>It causes them to accelerate downwards.</p> Signup and view all the answers

    When trapping electrons in a larger magnetic field, what type of motion do they exhibit?

    <p>Centripetal motion.</p> Signup and view all the answers

    If the electric field strength is increased, what is the likely effect on the electron's path in Thomson's experiment?

    <p>The electrons will curve more sharply.</p> Signup and view all the answers

    What is the significance of the velocity of an electron being almost 10% the speed of light in Thomson's findings?

    <p>It highlights relativistic effects on electrons.</p> Signup and view all the answers

    What was the main outcome of J.J. Thomson's first experiment with cathode rays?

    <p>Thomson determined that cathode rays were composed of negatively charged particles.</p> Signup and view all the answers

    What breakthrough did Thomson achieve in his third experiment?

    <p>Measurement of the charge-to-mass ratio of cathode rays.</p> Signup and view all the answers

    Why did Thomson build a nearly perfect vacuum tube for his second experiment?

    <p>To prevent stray air molecules from affecting the results.</p> Signup and view all the answers

    What can be concluded about the charge-to-mass ratio based on Thomson's findings?

    <p>It is the first quantitative measurement of a property of cathode rays.</p> Signup and view all the answers

    Which aspect of Thomson's cathode ray tube experiments was crucial for understanding atomic structure?

    <p>The determination of the relationship between charge and mass of electrons.</p> Signup and view all the answers

    What was the significance of the electric field in Thomson's second experiment with cathode rays?

    <p>It helped in deflecting the rays according to their charge.</p> Signup and view all the answers

    What did Thomson's exploration of cathode rays ultimately reveal about atoms?

    <p>Electrons exist as distinct particles within atoms.</p> Signup and view all the answers

    What was the role of J.J. Thomson's assistants in his research?

    <p>They contributed to different aspects of his research and also won Nobel Prizes.</p> Signup and view all the answers

    What was the initial belief of J.J. Thomson regarding the composition of atoms?

    <p>Atoms are entirely made up of electrons.</p> Signup and view all the answers

    What does the charge-to-mass ratio indicate about cathode rays according to Thomson's findings?

    <p>They are highly concentrated charges.</p> Signup and view all the answers

    What is the primary concept of Thomson's Plum Pudding model of the atom?

    <p>Positive and negative charges are evenly distributed.</p> Signup and view all the answers

    What did Thomson conclude about the nature of the electrons after reviewing cathode rays?

    <p>Electrons must be charged and light.</p> Signup and view all the answers

    How does Thomson's Plum Pudding model visualize the structure of an atom?

    <p>As a lump of positive material with electrons within.</p> Signup and view all the answers

    Why did Thomson believe there must be a positive substance in atoms?

    <p>To balance the electrons' negative charges.</p> Signup and view all the answers

    What nickname is commonly given to Thomson's model of the atom?

    <p>Raisin bun model.</p> Signup and view all the answers

    How are the electric and magnetic forces related when they are in balance?

    <p>The electric and magnetic forces are equal in magnitude.</p> Signup and view all the answers

    What is the correct formula to find the velocity of electrons in a velocity selector?

    <p>$v = \frac{E}{B}$</p> Signup and view all the answers

    What happens to electrons moving at the specific velocity defined by the velocity selector formula?

    <p>They experience no net force.</p> Signup and view all the answers

    If an electric field of $7.62e7$ N/C and a magnetic field of $3.65$ T are applied, what is the calculated velocity of the electrons?

    <p>$2.09e7$ m/s</p> Signup and view all the answers

    What does the variable 'B' represent in the velocity selector formula?

    <p>Magnetic field strength</p> Signup and view all the answers

    In the context of the velocity selector setup, why is it significant that the electrons are moving at almost 10% the speed of light?

    <p>It demonstrates the effectiveness of the setup in selecting specific velocities.</p> Signup and view all the answers

    What does the equation $F_e = F_m$ imply about the system of forces acting on the electrons?

    <p>The two forces must always be equal for stability.</p> Signup and view all the answers

    What does the relationship $E = vB$ represent in the context of the experiment?

    <p>The electric field strength is dependent on velocity and magnetic field strength.</p> Signup and view all the answers

    What is the calculated charge-to-mass ratio determined by the experiment?

    <p>1.70e11 C/kg</p> Signup and view all the answers

    What is the significance of the velocity calculated for the electron, specifically $3.2068966e7$ m/s?

    <p>It is the speed at which electric and magnetic forces balance.</p> Signup and view all the answers

    How does the calculated charge-to-mass ratio compare to the accepted theoretical value?

    <p>It is very close to the accepted value.</p> Signup and view all the answers

    What is the role of the magnetic field in calculating the charge-to-mass ratio?

    <p>It determines the radius of the electron path.</p> Signup and view all the answers

    Which of the following formulas is critical in determining the charge-to-mass ratio during Step Two of the experiment?

    <p>$q = mBr$</p> Signup and view all the answers

    What does the variable 'r' represent in the context of the equations used to find the charge-to-mass ratio?

    <p>Radius of the electron's circular path</p> Signup and view all the answers

    In the experimental calculations, what is implied if the calculated charge-to-mass ratio has a percent error?

    <p>There is room for improvement in the accuracy of measurements.</p> Signup and view all the answers

    What constant represents the theoretical value of charge used in the charge-to-mass ratio calculation?

    <p>1.60e-19 C</p> Signup and view all the answers

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