Digital Electronic
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Questions and Answers

What is the phenomenon of ejection of electrons from a metal surface by the application of heat called?

  • Electron emission
  • Thermal expansion
  • Electromagnetic induction
  • Thermionic emission (correct)

    • Who discovered the phenomenon of thermionic emission?

  • Richardson
  • Edison (correct)
  • Faraday
  • Dushman

    • What is the unit of the emission constant A in the Richardson-Dushman equation?

  • joule per kelvin
  • ampere per kelvin
  • ampere per square meter-kelvin squared (correct)
  • volt per square meter

    • What is the term for the current flowing due to thermionic emission?

    <p>Thermion current (C)</p> Signup and view all the answers

    What is the term for the emitted electrons in thermionic emission?

    <p>Thermions (C)</p> Signup and view all the answers

    What is the term for the minimum energy required to eject an electron from a metal surface?

    <p>Work function (C)</p> Signup and view all the answers

    What are the two main categories of electronics?

    <p>Valve and Semiconductor Electronics (B)</p> Signup and view all the answers

    What is the force that prevents free electrons from escaping the surface of a metal?

    <p>Coulombian force (C)</p> Signup and view all the answers

    What is the energy level at which the probability of finding an electron is 50%?

    <p>Fermi energy level (D)</p> Signup and view all the answers

    What is the minimum energy required to remove an electron from the surface of a metal?

    <p>Work function (D)</p> Signup and view all the answers

    What is the process of electron emission where electrons are emitted due to thermal energy?

    <p>Thermionic emission (A)</p> Signup and view all the answers

    What is the work function of oxide-coated tungsten?

    <p>1 eV (C)</p> Signup and view all the answers

    What is the direction of dependence of thermion current density on absolute temperature?

    <p>directly proportional to T^2 (B)</p> Signup and view all the answers

    What is the unit of the Boltzmann constant in the Richardson-Dushman equation?

    <p>J/K (C)</p> Signup and view all the answers

    What is the exponent of T in the Richardson-Dushman equation?

    <p>-2 (A)</p> Signup and view all the answers

    What is the dependence of thermion current density on emission constant A?

    <p>directly proportional to A (A)</p> Signup and view all the answers

    What is the kinetic energy of an electron required to overcome the barrier potential energy and come out of the metal surface?

    <p>Greater than binding energy (D)</p> Signup and view all the answers

    What is the difference between the binding energy and Fermi energy of a metal?

    <p>Work function (A)</p> Signup and view all the answers

    Which of the following types of electron emission requires heat to emit electrons from a metal?

    <p>Thermionic emission (D)</p> Signup and view all the answers

    Which type of electron emission does not require an external energy source?

    <p>Field emission (B)</p> Signup and view all the answers

    What is the energy level below which an electron is bound to the metal surface?

    <p>Ground energy level (D)</p> Signup and view all the answers

    What is the effect of increasing the absolute temperature on the exponential term of the Richardson-Dushman equation?

    <p>The exponential term increases (D)</p> Signup and view all the answers

    What is the effect of increasing the emission constant on the current density in the Richardson-Dushman equation?

    <p>The current density increases (A)</p> Signup and view all the answers

    What is the relationship between the thermion current density and the absolute temperature in the Richardson-Dushman equation?

    <p>The thermion current density is proportional to the square of the absolute temperature (C)</p> Signup and view all the answers

    What is the physical significance of the Boltzmann constant in the Richardson-Dushman equation?

    <p>It relates the thermal energy to the absolute temperature (B)</p> Signup and view all the answers

    What is the primary reason why free electrons in a metal experience a barrier on the surface?

    <p>Due to the attractive Coulombian force (B)</p> Signup and view all the answers

    What is the significance of the Fermi energy level in a metal at 0K temperature?

    <p>It is the energy level at which the probability of finding an electron is 50% (C)</p> Signup and view all the answers

    What is the difference between the binding energy and the Fermi energy of a metal?

    <p>The binding energy is greater than the Fermi energy (C)</p> Signup and view all the answers

    What is the work function of a material related to?

    <p>The minimum energy required to take out an electron from the surface of the material (B)</p> Signup and view all the answers

    What is the process of electron emission in which electrons are emitted due to an applied electric field?

    <p>Field emission (C)</p> Signup and view all the answers

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