29 Questions
What is the term for the magnetic retentivity that remains in a substance even when the magnetic field is zero?
Residual magnetism
What is the point at which the material is totally demagnetized?
Point C
What is the energy loss caused by the friction of molecules in the core of electric machines?
Hysteresis loss
What is the direction of the magnetic field produced by an alternating current?
Continually changing direction
What is the purpose of the coercive force in a magnetic material?
To remove the material's retentivity
What is the term for the cycle of magnetization and demagnetization in a ferromagnetic material?
Hysteresis loop
What is the typical amount of energy stored in a piezoelectric generator after a tap or press?
0.00001 joules
What is the main goal of improving the piezoelectric material itself?
To make the material more efficient at converting mechanical energy into electrical energy
Why is placing the piezoelectric material in certain locations a focus of research?
To increase the frequency of deformation
What is the piezoelectric effect?
The conversion of mechanical energy into electrical energy
What is an example of a common piezoelectric material?
Quartz
How much energy does a typical cell phone battery store?
18,000 joules
What is the work function represented as for metals?
Фm
What is the energy difference between the conduction band minimum and the vacuum energy level?
Electron affinity
What type of contact is formed when a metal and a semiconductor material are brought together with no electron movement?
Ideal MS contact
What is the purpose of the Schottky diode when used as a rectifier contact?
To allow current flow in one direction
What is the condition for the formation of a Schottky contact when φm > φs?
The work function of the metal is greater than the work function of the semiconductor
What type of semiconductors can form the Schottky contact?
Both n-type and p-type semiconductors
What is the Schottky barrier?
The potential energy barrier formed at the metal-semiconductor junction
What is the consequence of electrons transferring from the semiconductor to the metal in a Schottky barrier contact?
A negative charge in the metal and a positive charge in the semiconductor
What is the energy difference between the band edge with majority carriers and the Fermi energy of the metal?
Barrier height ΦB
Under what condition is the equilibrium band structure for a metal and a n-type semiconductor established?
When the applied bias VA is 0V
What is the reason for the formation of a depletion region at the semiconductor surface?
The transfer of electrons from the semiconductor to the metal
What is the relationship between the work function of semiconductors and the electron affinity?
The work function of semiconductors is related to the electron affinity and the conduction band
What happens to the depletion region as the applied voltage is continuously increased?
It becomes thinner and finally disappears
Why does a positive current get generated across the MS junction?
More electrons diffuse from the semiconductor towards the metal
What is the effect of increasing the applied voltage on the electrons in the MS junction?
Electrons find it easier to overcome the surface barrier
What happens to the current as the VA is kept increasing?
It increases rapidly
What is the direction of the current in the MS junction when VA is positive?
From the semiconductor to the metal
Understand the concept of magnetism and its relation to magnetic fields. Learn about the hysteresis loop, residual magnetism, and coercive force. Test your knowledge of the saturation point, retentivity point, and demagnetization.
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