Advertisements
Advertisements
Question
The anode of a thermionic diode is connected to the negative terminal of a battery and the cathode to its positive terminal.
Options
No appreciable current will pass through the diode.
A large current will pass through the diode from the anode to the cathode.
A large current will pass through the diode from the cathode to the anode.
The diode will be damaged.
Advertisements
Solution
No appreciable current will pass through the diode.
If the anode is given a negative potential relative to the cathode, the electrons are pushed back to the cathode. Hence, no current will flow through the diode.
APPEARS IN
RELATED QUESTIONS
The work function of caesium metal is 2.14 eV. When light of frequency 6 × 1014 Hz is incident on the metal surface, photoemission of electrons occurs. What is the
- maximum kinetic energy of the emitted electrons,
- Stopping potential, and
- maximum speed of the emitted photoelectrons?
Quarks inside protons and neutrons are thought to carry fractional charges [(+2/3)e; (–1/3)e]. Why do they not show up in Millikan’s oil-drop experiment?
Why should gases be insulators at ordinary pressures and start conducting at very low pressures?
How will the thermionic current vary if the filament current is increased?
Would you prefer a material with a high work-function or a low work-function to be used as a cathode in a diode?
An isolated metal sphere is heated to a high temperature. Will it become positively charged due to thermionic emission?
Let i0 be the thermionic current from a metal surface when the absolute temperature of the surface is T0. The temperature is slowly increased and the thermionic current is measured as a function of temperature. Which of the following plots may represent the variation in (i/i0) against (T/T0)?
Answer the following question.
Define the term "Threshold frequency", in the context of photoelectric emission.
If a light of wavelength 330 nm is incident on a metal with work function 3.55 eV, the electrons are emitted. Then the wavelength of the wave associated with the emitted electron is (Take h = 6.6 × 10–34 Js)
Emission of electrons by the absorption of heat energy is called ____________ emission.
Why do metals have a large number of free electrons?
Consider Figure for photoemission.
How would you reconcile with momentum conservation? Note light (photons) have momentum in a different direction than the emitted electrons.
Give an example each of a metal from which photoelectric emission takes place when irradiated by
- UV light
- visible light.
Name the factors on which photoelectric emission from a surface depends.
The work function of a metal is 2.31 eV. Photoelectric emission occurs when the light of frequency 6.4 × 1014 Hz is incident on the metal surface. Calculate
- the energy of the incident radiation,
- the maximum kinetic energy of the emitted electron and
- the stopping potential of the surface.
