## 01/03/2020

### Basic Electronics Interview Question Answer - 1

 1 Explain the term : Electronics Electronics The electronics is a branch of science in which conduction of current is done by semiconductor device. 2 Which type of charge does the atom of nucleus have? Charge of atom The centrer part of the atom is called nucleus. It consists of protons and neutrons. The protons have positive charge but a neutron does not any charge. Therefore the nucleus is positive charged. 3 Explain : Atomic weight Atomic weight (A) The sum of the numbers of protons and numbers of neutrons in an atom is called as atomic weight. Atomic weight = Numbers of protons + Numbers of neutrons 4 Explain : Atomic number Atomic number (Z) The numbers of protons or numbers of electrons in an atom is called as atomic number. Atomic numbers  =  Numbers of protons                              =  Numbers of electrons 5 Give reason : The atom is electrically neutral The atom is called as electrically neutral because the center part of an atom consists of protons and neutrons. The protons have positive charge. The outer part of the atom consists of electrons. The electrons have negative charge. There are numbers of protons is equal to numbers of electrons in an atom. 6 How many electrons in the orbit of an atom? Numbers of electrons in the orbit = 2n2 Where n = orbit number No. of electrons in 1st orbit  = 2(1)2 = 2 No. of electrons in 2nd orbit = 2(2)2 = 8 No. of electrons in 3rd orbit = 2(3)2 =18 7 Why only electrons are affected by external magnetic or electric field? ( Why not Protons ) The center part of an atom consists of protons and its outer orbit consists of electrons. Charge of an electrons = 1.602 * 10-19 coulomb Mass of an electrons   =  9.0 * 10-31 Kg Therefore the ratio of the charge and mass of an electrons = 1.77 * 1011 coulomb / kg. It means that mass of electrons is very small as compared to its charge. The electrons are affected by the magnetic field due to this property. 8 Explain the terms : Valance electrons Valance electrons The electrons in the out most orbit / shell / energy level of an atom are known as valance electrons. The atomic number of carbon is six. It means that an atom of carbon consists of 6 electrons. The numbers of electrons in the orbit are : 1st orbit - 2 electrons and 2nd orbit - 4 electrons. Therefore the valance electrons of an atom of carbon are four. OR The valance electrons are the electrons that may participate in the formation of covalent bonds with other atoms. 9 Explain the term : Free electrons Free electrons The valance electrons which are loosely attached to the nucleus of an atom are called as free electrons. 10 Explain the term : Conductor Conductor It is a substance in which the numbers of valance electrons of an atom is less than four. OR It is a substance in which large numbers of free electrons are available which constitutes current when small potential difference is applied across it. 11 Explain the term : Semi – conductor Semiconductor It is a substance in which the numbers of valance electrons of an atom are equal to four. OR It is a substance in which only few free electrons are present which constitutes very small current when small potential difference is applied across it. 12 Explain the term : Insulator Insulator It is a substance in which the numbers of valance electrons of an atom are more than four. OR It is a substance in which no free electrons at room temperature. Therefore an insulator does not conduct any current even if potential difference is applied across it. 13 Explain the term : Electron emission Electron emission The process of liberating electrons from the surface of a substance is known as electron emission. 14 Explain the term : Work function Work function: It is addition energy required to emit an electrons from metal surface. If the total energy required to emit an electron from metal surface is 5.0 eV and energy already possessed by electron is 1.0 eV, the work function for that metal is 5.0 eV – 1.0 eV = 4.0 eV. 15 Explain the term : Electron volt ( eV ) Electron volt The joule is very large unit for computing energy of electrons. The electron volt is small unit for calculating energy of an electron. It is defined as the amount of energy required by the charge of an electron, when it moves through potential difference of 1.0 Volt. Charge of electron = 1.602 * 10 -19 Coulomb Therefore one electron volt ( 1eV) = ( 1.602 * 10 -19 )( 1.0) Joule =  1.602 * 10 -19 Joule 16 Describe the different methods of electron emission from metal surface. Methods of electron emission Field emission Thermionic emission Photo electric emission Secondary emission 17 Explain the term : Thermal emission Thermal emission It is a process in which electron emission is done from metal surface when thermal energy is supplied to it. 18 Explain the term : Secondary emission Secondary emission It is a process in which electron emits from metal surface when bombarding of high speed electron to metal surface. 19 Explain the term : Photo electric emission Photo electric emission It is a process in which electron emits when a beam of light strike to metal surface. 20 Explain the term : Valance band Valance band It is defined as the band of energy occupied by the valance electrons. The valance band is never empty.  It is either partially filled or completely filled with electrons. OR The electrons in the outermost orbit of an atom is known as valance band and energies occupied that band is known as valance band. 21 Explain the term : Conduction band Conduction band It is band of electrons which are responsible for conduction of current is known as conduction band. The insulator has empty conduction band whereas the conductor has partially filled conduction band.

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