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    8.work Function of Metal

    Uploaded by

    Ravi Kanth M N
    The document describes an experiment to determine the work function of a metal filament in a vacuum diode tube. Thermionic emission is used to emit electrons from the heated filament. Measurements of filament voltage, current, and plate current are taken at different filament temperatures. A graph of log(Ip/T2) vs 1/T is plotted, and the slope m is used to calculate the work function φ using the given formula. The experiment is repeated for different plate voltages, and the work function of the metal is reported.

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    8.work Function of Metal

    Uploaded by

    Ravi Kanth M N
    831 views3 pages
    The document describes an experiment to determine the work function of a metal filament in a vacuum diode tube. Thermionic emission is used to emit electrons from the heated filament. Measurements of filament voltage, current, and plate current are taken at different filament temperatures. A graph of log(Ip/T2) vs 1/T is plotted, and the slope m is used to calculate the work function φ using the given formula. The experiment is repeated for different plate voltages, and the work function of the metal is reported.

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    Original Title

    8.Work Function of Metal

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    The document describes an experiment to determine the work function of a metal filament in a vacuum diode tube. Thermionic emission is used to emit electrons from the heated filament. Measurements of filament voltage, current, and plate current are taken at different filament temperatures. A graph of log(Ip/T2) vs 1/T is plotted, and the slope m is used to calculate the work function φ using the given formula. The experiment is repeated for different plate voltages, and the work function of the metal is reported.

    Copyright:

    © All Rights Reserved
    Download as DOCX, PDF, TXT or read online from Scribd
    Download as docx, pdf, or txt
    831 views3 pages

    8.work Function of Metal

    Uploaded by

    Ravi Kanth M N
    The document describes an experiment to determine the work function of a metal filament in a vacuum diode tube. Thermionic emission is used to emit electrons from the heated filament. Measurements of filament voltage, current, and plate current are taken at different filament temperatures. A graph of log(Ip/T2) vs 1/T is plotted, and the slope m is used to calculate the work function φ using the given formula. The experiment is repeated for different plate voltages, and the work function of the metal is reported.

    Copyright:

    © All Rights Reserved
    Download as DOCX, PDF, TXT or read online from Scribd
    Download as docx, pdf, or txt
    of 3

    WORK FUNCTION OF A METAL

    Aim: To determine the work function of material of the filament of the vacuum diode tube.
    Apparatus: Vacuum diode, voltmeter, DC power supply, milliammeter.
    Formula: Work function () =

    2.303 K m
    1.6 1019

    eV

    Where K= Boltzmann constant = 1.38 10-23 J/sec


    m= slope
    Circuit diagram:

    Nature of graph:

    Theory:
    When a metal is heated, electrons are emitted from its surface. This phenomenon is called
    thermionic emission. This property is widely used in vacuum tubes, in which a metallic cathode
    19 B.Sc V semester Physics lab manual, Dept. of Physics, Govt. Science
    College, Chitradurga

    WORK FUNCTION OF A METAL


    is usually heated in order to supply the electron required for the operation of the at absolute zero
    kelvin.
    1) The height of the potential barrier can be taken equal to E f+ , where Ef is the Fermi
    energy level and is the work function.
    2) All the levels up to the Fermi levels are filled and the levels above the Fermi level are
    empty.
    3) No electrons can escape from the metal surface. The work function is the minimum
    energy required to remove an electron from the Fermi surface to the vacuum outside the
    metal.
    Procedure:
    Electrical connections are as shown in the circuit diagram. For the table-1 plate voltage
    Vp =50V as constant. The filament is heated by applying the voltage (V f) and corresponding
    filament current If and the plate current Ip are noted. The experiment is repeated for various
    values of Vf and each case Rf = Vf/If is calculated. The temperature of filament is calculated using
    formula T=To(RT/Ro)5/6, where Ro is the resistance at zero degree Celsius and its value is equal to
    0.72 for the material used in this experiment and R T is the resistance at Tk. The graph is drawn
    taking Log

    ( ITp )
    2

    along Y-axis and 1/T along X-axis. Graph is found to be a straight line with

    slope m. The work function is calculated using the formula.


    2.303 K m
    Work function () = 1.6 1019 eV.
    .
    The experiment is repeated for next saturated plate voltage i.e. Vp = 75V
    Observation:
    Ro is the resistance at zero degree Celsius = 0.72
    To is the temperature = 273 K
    Tabular column for the plate voltage, Vp = 50 V
    Vfin mA

    Ipin mA If in mA
    Rf =
    103

    Vf
    If

    T =T o (
    RT
    5/6
    Ro )

    ( TI p2 )
    10-11

    1
    T

    Log
    Ip
    T2

    ( )

    10-4

    20 B.Sc V semester Physics lab manual, Dept. of Physics, Govt. Science


    College, Chitradurga

    WORK FUNCTION OF A METAL

    Calculations:
    Work function of a metal is calculated by using the formula () =

    2.303 K m
    eV
    19
    1.6 10

    Result: The work function of the metal in the vacuum diode is found to be () =________eV

    21 B.Sc V semester Physics lab manual, Dept. of Physics, Govt. Science


    College, Chitradurga

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