Elements of Electronics Electronics Engineering Group

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2 Written as per the revised G Scheme syllabus prescribed by the Maharashtra State Board of Technical Education (MSBTE) w.e.f. academic year Elements of Electronics Electronics Engineering Group First Year Diploma Semester - II First Edition: November 2015 Salient Features Concise content with complete coverage of revised G-scheme syllabus. Simple and Lucid language. Neat, Labelled and Authentic diagrams. Illustrative examples showing detailed solution of numericals. MSBTE Theory Questions and Numericals from Summer-2007 to Winter Includes MSBTE Question Papers of Summer, Winter and Three Model Question Papers for practice. Important Inclusions: Additional Theory Questions, Practice Problems, Knowledge Bank. Printed at: Repro Knowledgecast Ltd., Mumbai No part of this book may be reproduced or transmitted in any form or by any means, C.D. ROM/Audio Video Cassettes or electronic, mechanical including photocopying; recording or by any information storage and retrieval system without permission in writing from the Publisher. TEID PREFACE : 971

3 PREFACE Target s Elements of Electronics is compiled with an aim of shaping engineering minds of students while catering to their needs. It is a complete & thorough book designed as per the new revised G-scheme of MSBTE curriculum effective from June Each unit from the syllabus is divided into chapters bearing specific objectives in mind. The sub-topic wise classification of this book helps the students in easy comprehension. Each chapter includes the following features: Theory is provided in the form of pointers. Neat labelled diagrams have been provided wherever required. Italicized definitions are hard to miss and help students map answers easily. Illustrative Examples are provided in order to understand the application of different concepts and formulae. By introducing them after formulae, these examples enable students to gain command over formulae. An array of problems from simple to complex are included. (Examples here are similar to problems asked in previous years MSBTE Question Papers and also problems important from examination point of view) Formulae are provided for quick recap and last minute revision. MSBTE Theory Questions covered in separate section to give a clear idea of the type of questions asked. (Reference of answer to each question is provided.) MSBTE Numericals till latest year are included with complete solutions. MSBTE Waveform Questions offer conceptual solutions to waveform based question. Additional Theory Questions help students to gain insight on the various levels of theory-based questions. Problems for Practice (With final answers) covers a variety of questions from simple to complex. Knowledge Bank is designed to enrich students by providing the knowledge required to understand the concept covered in syllabus but does not fall in the scope of syllabus. MSBTE Question Papers of years 2014 and 2015 are added at the end to make students familiar with the MSBTE examination pattern. A set of three Model Question Papers is designed as per MSBTE Pattern for thorough revision and to prepare the students for the final examination. From, Publisher Best of luck to all the aspirants!

4 SYLLABUS Topic and Contents Hours Marks Topic 1] Passive Components Students will be able to: Differentiate active & passive components by observation, specification & application. Use various passive components as per requirements and applications. 1.1 Resistor: [8 Marks] Classifications of resistors, material used for resistor General specification of resistor- maximum voltage rating, power rating, temperature coefficient, ohmic ranges, operating temperature Classification and application of resistor Colour coding: with three, four & five bands LDR Working, characteristics & application TDR- listing of its type Potentiometer : linear and logarithmic, constructional diagram, specifications, applications of carbon and wire wound resistor 1.2 Capacitor [6 Marks] Classification of capacitors, dielectric materials used in capacitor Capacitor specifications: working voltage, capacitive reactance, frequency characteristic Fixed capacitor : specifications & applications Electrolytic capacitor: constructional diagram & working Variable capacitors: requirement of variable capacitor, construction, working, specification of air gang, PVC gang capacitor, trimmer capacitor Coding of capacitors using numerals, colour band system 1.3 Inductor: [6 Marks] Introduction of magnetic materials- Ferromagnetic & ferrimagnetic, B-H curve, hard & soft magnetic material, concept of Hysterisis, permeability, corecivity, reluctivity & losses in magnetic material Faraday s laws of electromagnetic induction, self & mutual induced e.m.f. Induction Definition & expression (with simple derivation) of self inductance, mutual inductance, coefficient of coupling, Q factor, inductive reactance Constructional diagram & application of air core, iron core & ferrite core, inductor frequency range for- AF, RF, IF toroidal inductor. Working principle of slug tuned inductor Colour coding of inductor.

5 Topic 2] Semiconductor Diodes Specific objectives: Students will be able to: Draw symbol and constructional sketch of various types of semiconductor, optical diodes. List diodes for the various applications. Understand concepts of P-N junction diode, zener diode, special diodes, optical diodes with schematic symbols 2.1 P-N junction diodes Working principle, circuit diagram & characteristic of P-N junction diode, static & dynamic resistance, specification, forward voltage drop, maximum forward current power dissipation 2.2 Zener diode Constructional diagram, symbol, circuit diagram and characteristics of zener diode. Specification: Zener voltage, power dissipation, dynamic resistance 2.3 Special diodes Construction, symbol & applications of PIN diode, Schottky diode, Tunnel diode 2.4 Optical diodes Construction, symbol, operating principle & applications of LED, IRLED, Photo-diode, LASER diode Topic 3] Rectifiers and filters Specific objectives: Students will be able to: Draw circuit of different types of rectifiers. Compare different types of rectifiers with respect to their parameters and applications. Compare different types of filters. 3.1 Rectifiers: Need of rectifiers, types of rectifiers HWR,FWR (bridge and centre tap) circuit operation input/output waveforms for voltage & current Parameters of rectifier ( without derivation): Average d.c. value of current & voltage, ripple factor, ripple frequency, PIV of diode, TUF, efficiency of rectifier Comparison of three types of rectifiers 3.2 Filters: Need of filters Circuit diagrams, operation and input-output waveforms of following types of filters: Shunt capacitor Series inductor LC filter π filter Numerical examples based on parameters of rectifiers

6 Topic 4] Wave shaping circuit Specific objectives: Students will be able to: Draw circuit of different types of wave shaping circuits. Compare different types of wave shaping circuits with respect to the parameters and applications. 4.1 Linear wave shaping circuit Need of wave shaping circuits, comparison between linear and non-linear wave shaping circuits Operations of wave shaping circuits Linear circuits: RC integrator & differentiator 4.2 Non-linear wave shaping circuits Circuit diagram, operation, waveforms of different types of clippers using diodes: series, shunt, (biased and unbiased) Circuit diagram, operation, waveforms of different types of clampers: positive and negative Topic 5 D.C. circuits and Network Theorems Specific objectives: Students will be able to: Use basic rules of electrical circuits with the view of solving problems on electrical circuits. Use various theorems to determine unknown electrical quantities in the network 5.1 Fundamentals of D.C. circuit Review of Ohm s law Concept of open &short circuit Kirchhoff s current and voltage law Maxwell s loop current method Node analysis Concept of ideal & practical current and voltage sources, source conversion Star/Delta & Delta /Star conversion (no derivations) Network terminology- active, passive, linear, non-linear bilateral, unilateral network 5.3 Network theorem: Statement, explanation & applications of following Superposition theorem Thevenin s theorem Norton s theorem Maximum power transfer theorem Numerical examples on above topic. TOTAL

7 Contents Chapter No. Topic Page No. Unit - I: Passive Components 1 Resistors 1 2 Capacitors 26 3 Inductors 48 Unit - II: Semiconductor Diodes 4 Semiconductor Diodes 77 Unit - III: Rectifiers and Filters 5 Rectifiers Filters 139 Unit - IV: Wave Shaping Circuits 7 Wave Shaping Circuits 163 Unit - V: D.C. Circuits and Network Theorems 8 D.C. Circuits and Node Analysis Network Theorems 218 Model Question Papers Model Question Paper I 262 Model Question Paper II 265 Model Question Paper III 268 MSBTE Question Papers Question Paper Summer Question Paper Winter Question Paper Summer Question Paper Winter

8 Target Publications Pvt. Ltd. Basic Physics (F.Y.Dip.Sem.-1) Chapter 01: Resistors MSBTE Resistors UNIT I 1.1 Electronic Components 1.2 Resistors 1.2.(a) Characteristics of resistors 1.3 Colour coding of resistors 1.3.(a) 1.3.(b) 1.3.(c) Colour coding with four band system Colour coding with three band system Colour coding with five band system 1.4 Classification of resistors 1.5 Linear resistors 1.5.(a) 1.5.(b) 1.5.(c) 1.5.(d) Fixed linear resistors Carbon film resistor Wire wound resistors Carbon composition resistors 1.6 Variable linear resistors 1.6.(a) 1.6.(b) 1.6.(c) 1.6.(d) 1.6.(e) Potentiometers Linear potentiometers Logarithmic (non-linear) potentiometers Specifications and applications Comparison of linear and logarithmic potentiometer 1.7 Non-linear resistors 1.7.(a) 1.7.(b) 1.7.(c) Light dependent resistor (LDR) Thermistors (TDR) Comparison of TDR and LDR 1

9 Target Publications Pvt. Ltd. Elements of Electronics (F.Y.Dip.Sem.-2) (Electronics) MSBTE 1.1 Electronic components The components used in designing or assembling of an electronic circuit are called electronic components. Every circuit usually contains multiple electronic components such as diodes, resistors, capacitors, transistors etc. Basic classification of electronic components: Electronic components Passive components Active components Resistors Capacitors Inductors Electronic tubes Semiconductor devices Passive components: i. The electronic components, which by themselves are not capable of amplifying or processing an electrical signal are called passive components. ii. These components conduct current in both the directions hence are known as bilateral/ bidirectional devices. e.g. Resistors, capacitors, inductors. Active components: i. The electronic components, which by themselves are capable of amplifying or processing an electrical signal are called active components. ii. These components conduct the current only in one direction and therefore are known as unilateral/unidirectional devices. e.g. Electronic tubes and semiconductor devices such as diodes, transistors, FETs, UJTs etc. Comparison between passive and active components: Passive component Active component i. The electronic components which by The electronic components which by themselves are not capable of amplifying or processing an electrical signal are called passive components. themselves are capable of amplifying or processing on electrical signal are called active components. ii. It does not introduce any gain. It may introduce the gain. iii. It has bidirectional functions. It has generally unidirectional functions. iv. These components do not act as an energy These components act as an energy source. source. e.g. Resistors, inductors and capacitors Transistor, diodes and power devices. Discrete components: i. The components, which are discrete in nature i.e., individual form, are called discrete components. ii. These components may be active or passive in nature. e.g. Resistors, capacitors, transformers, semiconductor diodes, etc. 2

10 Target Publications Pvt. Ltd. Basic Physics (F.Y.Dip.Sem.-1) Chapter 01: Resistors MSBTE Non-discrete components: i. The components which are connected together to build a single circuit and not discrete in nature are called non-discrete components. ii. These may be active or passive components. iii. Combination of non-discrete components form integrated circuits. Parasitic components: i. The components do not exist physically, but are due to electrodes or wirings are called parasitic components. ii. Conceptually, they are present in the device and in the electronic circuits. iii. e.g. These components play an important role when circuit is operated at high frequency. Inter electrode capacitances, junction capacitances, stray capacitance, charge storage capacitances, diffusion capacitances etc. 1.2 Resistors i. The flow of electric current through any material encounters an opposing force. This opposing force is called resistance of the material and this property of a device is called resistor. ii. The passive component, which opposes the flow of electric current and has positive temperature coefficient of resistance is called a resistor. iii. It can conduct current in both directions and therefore is known as bilateral device. iv. According to Ohm s law: V = IR Resistance R = V I where, V is potential difference between two points of material and I is current flowing through it. v. a. The resistance (R) of a resistor is directly proportional to length (L) of material used i.e., R L and R is inversely proportional to area of cross-section of material used (A) i.e., 1 R A R L A b. Proportionality sign is removed by introducing proportionality constant which is called as specific resistance of the material. It is denoted by rho ( ). R = L A vi. vii. where, = Specific resistance of material used. Factors affecting resistance: a. Length b. Area of cross-section c. Nature of material d. Temperature Unit: The resistance is measured in ohm ( ). It is the smallest unit of resistance. Larger units of resistance are kilo ohm and mega ohm. 1 Kilo ohm = 1 k = Mega ohm = 1 M =

11 Target Publications Pvt. Ltd. viii. Symbol: R R Elements of Electronics (F.Y.Dip.Sem.-2) (Electronics) MSBTE Fixed resistor Variable resistor ix. Materials used for resistor: a. Nichrome b. Tungsten c. Bronze d. Eureka e. Manganese f. Constantan 1.2.(a) Characteristics of resistors: i. Resistance value ii. Temperature coefficient of resistance. iii. Voltage coefficient of resistance iv. Frequency range v. Tolerance (Accuracy) vi. Shelf life vii. Load life viii. Resistivity ix. Power handling capacity x. Working voltage. General specifications of resistor: i. Maximum voltage rating: a. The maximum voltage at which the resistor can operate without failure is called maximum voltage rating. OR The maximum voltage that can be applied to a resistor without any damage to it is called the voltage rating. b. It is given by V max = (power rating resistance value) 1/2 V max = (P R) 1/2 c. The working voltage is usually rated as d.c. value. ii. iii. Power rating: a. The maximum amount of heat dissipated by a resistor at maximum specified temperature without any damage to resistor is called power rating of a resistor. b. It is expressed in watt (W) at specified temperature. c. As temperature increases, power rating decreases. Temperature coefficient of resistance: a. The percentage change in resistance per unit change in temperature is called temperature coefficient of resistance. b. It is denoted by letter alpha ( ). c. The temperature coefficient can be positive or negative depending upon whether resistance increases or decreases with temperature. RT R 1 T2 d. Temperature coefficient ( ) = 10 6 (ppm / C) R (T T ) where, T1 1 2 R T 1 = value of resistance at temperature T 1 C = value of resistance at temperature T 2 C R T 2 4

12 Target Publications Pvt. Ltd. Basic Physics (F.Y.Dip.Sem.-1) Chapter 01: Resistors MSBTE iv. Tolerance: a. Tolerance of a resistor measures deviation of the resistance value from its actual (indicated) value in percent. Thus, tolerance is defined as the accuracy to which value of resistor can be made or selected. b. Tolerance indicates factor by which the actual value of the resistor may be either grater or smaller than specified value of the resistor. c. It may range from 0.001% to 20%. d. Different values of tolerance are due to different types of resistors and different materials used in making them. e. Significance of Tolerance: Low percent of tolerance means high manufacturing accuracy and high percent of tolerance indicates low manufacturing accuracy. v. Operating temperature: a. The maximum temperature, at which the resistor can be operated without failure is called maximum operating temperature. b. It is also called temperature rating. c. If operated above this temperature, resistor gets damaged. vi. vii. Wattage: a. The wattage of a resistor is the power handling capacity of a resistor. b. It is the amount of power it can dissipate without excessive heating. c. The power rating of a resistor is given in wattage. e.g. Normal available resistors have power ratings of 1/8 W, 1/4 W, 1/2 W, 1W, 2W. d. The size of resistor depends on its power handling capacity. Small resistors are designed to handle low powers. Resistivity (or specific resistance) is defined as the resistance of the piece of that material which is 1 metre long and of unit cross-sectional area. viii. Frequency range: a. The range of frequency, upto which the resistor offers pure resistance, is called frequency range. b. The resistor may be pure resistor at low frequency as it offers only resistance, but it may have capacitive or inductive impedance at high frequencies. ix. Shelf life is defined as the change in value of resistance during storage usually quoted for one year. x. Load life: a. Load Life is defined as the change in value of resistance after specified time, at specified temperature. b. Resistors are tested for change in resistance after 1000 hours at 70 C. xi. Ohmic range: a. Ohmic range of a resistor is defined as its minimum to maximum resistance value that can be manufactured. b. Ohmic range changes depending on the type of material and different manufacturing processes used for a resistor. c. It ranges from few ohms to several mega ohms. 5

13 Target Publications Pvt. Ltd. Elements of Electronics (F.Y.Dip.Sem.-2) (Electronics) MSBTE 1.3 Colour coding of resistors The colour code is the convenient way to indicate the value of the resistance, in the form of circular colour bands or rings around the resistor. Colour (bands) code 1 st Colour band Three band system 1 st Colour band Four band system 4 th Colour band Five band system 1 st Colour band 1 st significant digit Multiplier 2 nd significant digit 1 st significant Tolerance digit Multiplier 2 nd significant digit Tolerance 1 st, 2 nd, 3 rd Multiplier Significant digit The colour coding of resistor is standardized by Electronic Industries Association (EIA). Colour coding for Resistors: Colour First Band Second Band Third Band Fourth Band (Multiplier) (Tolerance) Black = 1 Brown = 10 1% Red = 100 2% Orange Yellow Green % Blue % Violet % Grey % White Gold 10 1 = 0.1 5% Silver 10 2 = % No colour 20% To remember the colours in order, learn the Mnemonics : Black Brown Rods Of Your Gate Became Very Good When Given Silver paint (a) Colour coding with four band system: i. In colour code with four band system, a resistor has four bands on it. Each colour represents a definite significant value.

14 Target Publications Pvt. Ltd. Basic Physics (F.Y.Dip.Sem.-1) Chapter 01: Resistors MSBTE ii. iii. iv. Value of the first two colours denote the first two digits, say x and y. The third colour denotes the digit, say z to be used as a power of 10 multiplier. So, the resistance value is xy 10 z. The fourth band indicates the tolerance. e.g. Let the colours of the three rings, of a resistor starting from one end be brown, red and orange. Hence, referring to colour code table x = 1, y = 2, z = 3 Resistance = xy 10 z = = 12 k To find out the range of the resistor: a. The value of tolerance in percent is multiplied with value of resistor and total tolerance value is obtained. b. This tolerance value is then subtracted from actual value of resistance and is added to actual value of resistance. Thus, range of resistance = xy 10 z T% Colour code for resistance below 10 : i. For the resistance with values less than 10 the third band is either gold or silver. ii. This serves as a fractional multiplier. iii. If the third band is gold then the first two digits are multiplied by 0.1. If it is silver then the first two digits are multiplied by iv. The fourth band represents the tolerance value. Illustrative examples: Example 1 Evaluate resistance value for the colour-coded resistor: Green Blue Red Golden. Given : Green Blue Red Gold To find: Value of resistance Formula: Value of resistance = (xy 10 z ) T% Colour Green Blue Red Gold x y z T% Code Hence x = 5, y = 6, z = 2, T = 5% Comparing with formula, Value of resistance = ( ) 5% = % = 5.6 k 5% Ans: The value of resistance is 5.6 k 5%. Example 2 A carbon resistor has the following colour bands in order: Red, green, blue and silver. How much resistance range is indicated? Solution: Given: Red Green Blue Silver To find: Range of resistance Formula: Value of the resistance = xy 10 z T% 7

15 Target Publications Pvt. Ltd. Elements of Electronics (F.Y.Dip.Sem.-2) (Electronics) MSBTE 8 Colour Red Green Blue Silver x y z T% Colour code Here, x = 2, y = 5, z = 6, T = 10% Comparing with formula, Value of resistance = % To find out range, 10% of ( ) = = , the range of the resistance is ( %) = ( ) i.e., between and Ans: The range of the resistance is ( ) or between and Example 3 The colour bands denoted on the resistor are yellow, green, red, no colour. What is the range of resistance value? Solution: Given: Yellow Green Red No colour. To find: Range of resistance Formula: Range of the resistance = xy 10 z T% Colour Yellow Green Red No colour x y z T% Colour code % Here, x = 4, y = 5, z = 2, T% = ± 20%. Comparing with formula, The value of the resistance = ( ) 20% To find out range, 20% of 4500 = = 900, 100 the range of the resistance = ( ) i.e., between 3600 and Ans: The range of resistance is ( ) or between 3600 and Example 4 A carbon resistor has a resistance range of ( %). Write down the colour of the bands in order. Solution: Given: Value of resistance = ( %) To find: Colour of the bands in order Formula: Value of resistance = xy 10 z T%

16 Target Publications Pvt. Ltd. Basic Physics (F.Y.Dip.Sem.-1) Chapter 01: Resistors MSBTE Value of resistance = ( %) = % Comparing this with the formula, here x = 6, y = 7, z = 5, T = 5% Referring to colour code table, The first ring/colour for x = 6 is blue. The second ring/colour for y = 7 is violet, The third ring/colour for z = 5 is green. The fourth ring/colour for T = 5% is gold. Hence, colour bands on the given resistor are Blue Violet Green Gold Ans: The colour of the bands of the resistor in order are Blue Violet Green Gold. Example 5 Using colour code, write the colour codes for the following resistors 4.7 Ω, ± 5%. Given: Value of resistance = (4.7 5%) To find: Colour of the bands in order Formula: Value of resistance = xy 10 z T% Value of resistance = (4.7 5%) = % Comparing this with the formula, here x = 4, y = 7, z = 1, T = 5% Referring to colour code table, The first ring/colour for x = 4 is Yellow. The second ring/colour for y = 7 is Violet. The third ring/colour for z = 1 is Gold. The fourth ring/colour for T = 5% is Gold. Hence, colour bands on the given resistor are Yellow Violet Gold Gold Ans: The colour of the bands of the resistor are Yellow Violet Gold Gold. 1.3.(b) Colour coding with three band system: For resistor with only three colour bands and no fourth tolerance band, its value is calculated as explained for the four band colour code system and the tolerance is taken as 20% default. Illustrative Example: For the resistor shown below find the value and the tolerance. A B C Yellow Brown Solution: Violet Given: Yellow Violet Brown To find: Value of resistance, tolerance Formula: Value of resistance = xy 10 z T % 9

17 Target Publications Pvt. Ltd. Elements of Electronics (F.Y.Dip.Sem.-2) (Electronics) MSBTE The value of the given resistance is, Colour Yellow x Violet y Brown z code Here, x = 4, y = 7, z = 1 From formula, Value of resistance = T % = 470 T % As the fourth band is absent, the tolerance value is 20%. Ans: The value of resistance is 470 and its tolerance is 20%. 1.3.(c) Colour coding with five band system: i. The five band colour code is used for higher precision or lower tolerance resistors such as 1%, 0.5%, 0.25%, 0.1% etc. ii. The first three colour bands represent the significant digits, the forth band is a multiplier and the fifth band is the tolerance band. iii. If in the five band resistors, fourth band is gold or silver, then it indicates tolerance and fifth band indicates temperature coefficient. These resistors are either old or specified resistors as shown below. Tolerance Temperature coefficient 1 st Significant digit Multiplier 2 nd Significant digit Old / specified resistor Illustrative Example: For the five band colour code shown below, find the resistance value and the tolerance Yellow Golden Grey Brown Black Solution: Given: Five band colour code Blue, Grey, Black, Brown, Golden To find: Value of resistance, tolerance Formula: Value of resistance = xyz 10 n T% The value can be found as follows: Colour Blue Grey Black Brown Golden (Digit 1) (Digit 2) (Digit 3) (Multiplier) (Tolerance) Code %

18 Target Publications Pvt. Ltd. Basic Physics (F.Y.Dip.Sem.-1) Chapter 01: Resistors MSBTE Here, x = 6, y = 8, z = 0, n = 1, T = 5% From formula, The value resistance = = 6.8 k and tolerance is 5% Ans: The value resistance is 6.8 k and tolerance is 5%. Knowledge Bank Another common type at marking is four character label that uses both digits and letters. An alphanumeric label typically consists of only 3 digits or two or three digits and one of the letters R (ORE), K or M. The letter is used to indicate the multiplier and its position indicates decimal point placement. R (ORE) indicates multiplier of 1, K indicates multiplier of 1000 and M indicates multiplier of 10,00, R = 22 1 st 2 nd Decimal digit digit point and multiplier 2 M 2 = 2.2 M 1 st Decimal 2 nd digit point and digit multiplier K = 220 k 1 st 2 nd 3 rd Decimal digit digit point digit and multiplier Tolerance value can also be represented using alphabets as follows: a. F = 1% 1% b. G = 2% c. J = 5% d. K = 10% e. M = 20% Thus, complete value of resistance with its tolerance value can be printed in alphanumeric form. i. 82 KF = 82 k, 1% ii. 2E 5M: 2.5, 20% iii. 8M 6J: 8.6 M, 5% iv. 33 K6 K: 33.6 k, 10% 1.4 Classification of resistors Resistors Linear resistors Non-linear resistors Fixed resistors Variable resistors Thermistor (TDR) Photo resistor (LDR) Varistor (VDR) Carbon composition Metal film Carbon film Wirewound Rheostats Potentiometer Trimmers (preset) Thin film 1.5 Linear resistors Thick film Linear potentiometer Logarithmic potentiometer i. The resistors through which the current flowing is directly proportional to the applied voltage are called linear resistors. 11

19 Target Publications Pvt. Ltd. Elements of Electronics (F.Y.Dip.Sem.-2) (Electronics) MSBTE ii. iii. Resistance value of linear resistor does not change with the variations in applied voltage, temperature and light intensity. Linear resistors are of two types fixed resistors and variable resistors. 1.5.(a) Fixed linear resistors: The linear resistors whose resistance value does not change with the variation in applied voltage, operating temperature and light intensity and also it has fixed value of resistance that cannot be varied manually are called fixed linear resistors. Application of fixed linear resistors: i. Used to control the flow of current ii. Used in biasing of a device iii. Used in coupling networks iv. Used in feedback networks v. Used in amplifier circuits vi. Used in waveform generators vii. Used in oscillators viii. Used in radio and T.V. receivers Carbon film resistor, wire wound resistor, carbon composition resistor are some types of fixed linear resistors. 1.5.(b) Carbon film resistor: Concept: The film resistors are made by depositing a thin layer of resistive material on the surface of an insulated rod, tube or plate made up of ceramic or glass. The materials used for deposition is pure carbon hence, the name. Construction: End cap Insulating protective coating (lacquer or plastic) Tinned lead Insulating rod Spiralled off resistive coating i. High grade non-porous electrical insulator cores with fine surface are heated in specially constructed furnaces with accurate temperature. ii. The hydrocarbon is passed through the furnace iii. The hydrocarbon cracks at high temperature inside furnace and forms a diamond hard crystalline carbon coating on the insulator core. iv. The coated rods are press fitted with brass caps which are pre welded with electro tinned electrolytic copper wire. v. The desired values are obtained by either trimming the layer thickness or by cutting helical grooves, of suitable pitch along its length. vi. During this process, the value of resistance is monitored constantly the cutting of grooves is stopped as soon as the desired value of resistance is obtained. 12

20 Target Publications Pvt. Ltd. Basic Physics (F.Y.Dip.Sem.-1) Chapter 01: Resistors MSBTE vii. The contact caps are fitted on both ends. The load wires made of tinned copper are then welded to this end caps. viii. Carbon film resistors are obtained with tolerance of 1% Specifications: i. Resistance value: 100 /sq. inch ii. Tolerance: 1 % or less iii. Temperature coefficient: 100 to 200 ppm/ C iv. Maximum overload voltage: 500 V to 600 V v. Power rating at 70 C: 0.5 W or 0.25 W Applications: i. Used in all types of precision equipments ii. Used in defence communication iii. Used in industrial control iv. Used in computers. 1.5.(c) Wire wound Resistors: Concept: The power handling capacity of carbon composition resistors is very low. It can be increased by using the metallic wire instead of carbon materials as a resistive element. Construction: Wire soldered Ceramic rod Lead wire Wire wound on ceramic rod Terminal Hollow tube outer coating Resistance wire winding i. The wire wound resistor is manufactured by winding resistance wire on to an insulating frame. ii. The common materials used are a. Nichrome (Nickel chromium) b. Copper Nickel alloys (Eureka) c. Alloys of Nickel and Silver iii. The wire is produced by drawing the material through a suitable dye. iv. The ends of the winding are attached to metal terminals inserted in the core. v. The tinned copper leads are attached to these metal pieces. vi. The whole resistor is then covered in some insulating material (cement, vitrous enamel and lacquer), which provides the resistor protection against moisture and environmental condition. 13

21 Target Publications Pvt. Ltd. Elements of Electronics (F.Y.Dip.Sem.-2) (Electronics) MSBTE Specifications: i. Ohmic range: 0.4 to 10 6 ii. Temperature coefficient: 5 ppm/ C iii. Wattage: 200 W iv. Working voltage: < 300 V v. Tolerance: ±1% or ±5% Applications: i. Used in regulated power supplies. ii. Used in multimeter. iii. Used in Wheatstone bridge. iv. Used when high power handling capacity is required in small size. 1.5.(d) Carbon composition resistors: Concept: This is the most widely used fixed resistor in discrete circuit. It is made up of carbon black, resin binder and refractory filings. They are mixed in proper proportions to get desired value of resistance. Construction: Solder coated lead Colour coding Moulded body Solid resistance element Embedded lead OR End cap/ Contact Connecting leads Color code Carbon composition containing solid rod of carbon granules Connecting leads 14 i. The mixture is black powder which is compressed into the shape of resistor and cured in an oven to solidify. ii. Commonly, the resistance element is a simple rod of carbon powder. It is enclosed in a plastic case for insulation and mechanical strength. iii. The two ends of the carbon resistance element (or rod) are joined to metal caps with leads of tined wire. iv. These two leads are provided for soldering the resistor into the circuit. Specifications: i. It has wide range of resistance values. ii. It is a general purpose resistor. iii. It has tolerance of 5%, 10% or 20% iv. It has temperature coefficient of 1200 ppm/ C.

22 Target Publications Pvt. Ltd. Basic Physics (F.Y.Dip.Sem.-1) Chapter 01: Resistors MSBTE v. It has wide temperature range, typically 55 C to C. vi. It is capable of operating safely upto about 800 V. vii. It has voltage coefficient of 0.5 V d.c. viii. It is available in the power ratings of 1/8 W, 1/4 W, 1/2 W, 1 W and 2 W. ix. It has frequency range upto 20 khz. x. The thermal noise and current noise are present. Applications: i. Used in high frequency low power applications. ii. Used in the power control circuits. iii. Used in general purpose electronic equipments such as potential divider, amplifiers, zener voltage regulator. iv. Used in d.c. power supplies. v. Used in radio and T.V. receivers (low wattage blocks). 1.6 Variable linear resistors i. The linear resistor, whose resistance value does not change with the variation in applied voltage, operating temperature and light intensity but its resistance value can be varied manually to its maximum specified limit, is called variable linear resistor. ii. Trimmers, rheostat, potentiometers are some types of variable linear resistors. 1.6.(a) Potentiometers: Concept: The potentiometers are variable linear resistors that deliver an output voltage representing some function of an applied voltage and shaft position. It is small in size and is usually referred as pot. Applications of potentiometers: i. Used as a voltage divider in the electronic circuits. ii. Used as a volume control, tone control or brightness controls in radio and T.V. receivers. Types: Depending upon the type of resistance element, the potentiometers come in many types such as wire wound potentiometer, linear potentiometer, logarithmic potentiometers etc. 1.6.(b) Linear potentiometers: i. The potentiometers in which the relationship between the resistance and the rotational characteristics is a straight line are called linear potentiometers. ii. For linear potentiometers, overall thickness of the material is uniform and its resistivity is uniform over the entire length of element. Characteristics: Resistance Linear relation O Rotation of shaft 15

23 Target Publications Pvt. Ltd. Elements of Electronics (F.Y.Dip.Sem.-2) (Electronics) MSBTE 1.6.(c) Logarithmic (non-linear) potentiometers: i. The potentiometer in which the relationship between the resistance and the rotational characteristics is a logarithmic (i.e., non-linear), are called logarithmic potentiometer. ii. For logarithmic potentiometer, resistivity of the material is not uniform but it is nonuniform over the entire length of the material used. Characteristics: Resistance 16 O Rotation of shaft 1.6.(d) Specifications and applications: Specifications of linear and nonlinear potentiometers: i. Ohmic range: 10 Ω to 125 kω ii. Power rating : 100 watt to 200 watt iii. Tolerance: ± 20 to 25% iv. Voltage Rating: 5 V-500 V v. Operating Temperature: 100 C vi. Power wattage: 1 W and 3 W Applications of linear and nonlinear potentiometers: i. Used in d.c. power supplies to vary the output voltage. ii. Used in signal generators to vary the amplitude of output voltage. iii. Used in radio receiver (as a volume control). iv. Used in T.V. receiver as volume control. v. Used in amplifier circuits. vi. Used in the public address amplifier (P.A.) system. vii. Used as potential dividers. viii. Used for panel control in receivers, generator etc. 1.6.(e) Comparison of linear and logarithmic potentiometer: No. Parameter linear potentiometer logarithmic potentiometer i. Relation between It has a linear variation of It has a logarithmic variation of resistance and resistance with each degree of resistance with each degree of rotation of shaft rotation of its shaft. rotation of its shaft. ii. Resistivity Resistivity of material is Resistivity of material is different uniform and same over the through the length. entire length. iii. Manufacturing It is produced by taking resistive segments of uniform thickness over entire length of the segment. It is produced by combining segments of resistance mixers having different resistivity.

24 Target Publications Pvt. Ltd. Basic Physics (F.Y.Dip.Sem.-1) Chapter 01: Resistors MSBTE iv. Characteristic curve Resistance Resistance Rotation of shaft v. Costing Linear potentiometers are less expensive as compared to logarithmic potentiometers. vi. Application In consumer electronics, user control uses linear potentiometers. Rotation of shaft Logarithmic potentiometers are more expensive as compared to linear potentiometers. Logarithmic potentiometers are often used in connection with audio amplifiers. 1.7 Non-linear resistors i. The resistor, through which the flow of current is not directly proportional to the applied voltage is called non-linear resistor. ii. These resistors are made from semiconducting materials. iii. The value of non-linear resistor depends on applied voltage, temperature and light intensity. Types of non-linear resistors: i. Thermistor i.e., temperature dependent resistor (TDR). This includes NTC thermistor and PTC thermistor. ii. Varistor i.e., voltage dependent resistor (VDR). iii. Light dependent resistor (LDR) / photo resistor. 1.7.(a) Light dependent resistor (LDR): Concept: i. When the light is incident on the semiconductor materials, the covalent bonds are broken and the charge carriers i.e., electron-hole pairs are produced. ii. The amount of intensity of light on the surface of the semiconductor material determines the number of electron-hole pairs generated. iii. As the light intensity increases, conductivity of semiconductor material increases and the resistance decreases. This is called as photoconductive effect. iv. Thus, the resistance of the material varies inversely with the amount of light intensity. Photoconducting material Photon Motion of electrons + Electron hole pair + Principle of operation of a photoconductor 17

25 Target Publications Pvt. Ltd. Elements of Electronics (F.Y.Dip.Sem.-2) (Electronics) MSBTE Construction: i. The photoconductive cells or light dependent resistors (LDR) are manufactured from photo-conductive semiconductor materials and make use of photoconductive effect. ii. iii. These are made in disc-shapes with wire lead ends on one side. They have ceramic substrate over which a layer of cadmium sulphide (CdS) or lead sulphide (PbS) is deposited in zigzag form to increase the length and in turn its resistance value. iv. Depending on the thickness, surface area and length of the layer, the resistance changes. v. Electrodes are formed by evaporating metal in vacuum. Leads are connected and put in plastic case as shown in the figure below. Light Glass window Metallic or plastic body Substrate Photo resistive Material (cadmium sulphide) Leads vi. Photo resistors offer resistance of several mega ohms in complete darkness and less than 100 under bright illumination. Symbol: Variation of resistance with intensity of light: Dark resistance Resistance (k ) O Intensity (I) 18 From the graph it is clear that the resistance of the semiconductor material decreases with increase in the light intensity. Specifications: i. Resistance range: 400 Ω to 400 kω ii. Power dissipation: 100 mw max. iii. Dark resistance: 20 MΩ iv. Response time: 45 ms

26 Target Publications Pvt. Ltd. Basic Physics (F.Y.Dip.Sem.-1) Chapter 01: Resistors MSBTE Applications: i. Used for automatic contrast and brightness control in T.V. receivers. ii. Used in street light control circuits. iii. Used in security alarms. iv. Used in smoke detectors. v. Used in photosensitive relay. vi. Used as a proximity switch. vii. Used in optical coding. viii. Used in light (flux) meter. ix. Used in camera light meters. x. Used in the infrared astronomy. 1.7.(b) Thermistors (TDR): Concept: i. It is a temperature sensitive resistor or temperature dependent resistor (TDR). ii. It is a nonlinear resistor for which the variation in temperature is reflected through an appreciable variation of the resistance of the device. iii. The resistance of a thermistor may increase or decrease with the rise in temperature. T T Symbol: Types: Depending on the value of temperature coefficient of resistance thermistors are classified as: NTC (negative temperature coefficient) and PTC (positive temperature coefficient). NTC thermistors: i. NTC thermistors have negative temperature coefficient of resistance hence resistance of the resistive material decreases with increase in temperature, i.e., R 1/T. ii. Graph of resistance v/s temperature for NTC: Resistance iii. Temperature Characteristics NTC thermistors are used when continuous change of resistance is required over wide range of temperature. PTC thermistors: i. PTC thermistors have positive temperature coefficient of resistance hence resistance value decreases with decrease in temperature i.e., R T. ii. Graph of resistance v/s temperature for PTC: 19

27 Target Publications Pvt. Ltd. Elements of Electronics (F.Y.Dip.Sem.-2) (Electronics) MSBTE Resistance Temperature Characteristics iii. PTC thermistors are used when a drastic change in resistance is required at specific temperature. Applications of thermistors: i. Used for measurement of temperature. Its large temperature coefficient provides good accuracy and resolution. ii. Used for temperature compensation over a wide range of temperature. iii. Used for measurement of power at high frequency. iv. Used for measuring thermal conductivity. v. Used for thermal relay. vi. Used in biomedical instrumentation. 1.7.(c) Comparison of TDR and LDR: Points TDR LDR i. Working principle The resistance depends on the change in temperature. The resistance depends on the change in light intensity. ii. Material used for construction Cadmium sulphide (CdS), Lead sulphide (PbS) iii. Characteristic curve For NTC: Metallic oxides of cobalt, nickel, manganese etc. For PTC: Germanium or silicon Resistance NTC Temperature iv. Application a. Temperature measurement a. Automatic contrast b. Liquid level measurement b. proximity switch c. Temperature compensation c. Security alarms in electronic circuits d. Biomedical instrumentation d. Smoke detectors PTC Dark resistance Resistance (k ) O Intensity (I) 20

28 Target Publications Pvt. Ltd. Formula Value of resistance: R = xy 10 z T% MSBTE Theory Questions 1. Define active and passive components. [S-07] [2 M] Ans: Refer Name any four characteristics of resistor. [S-07] [2 M] Ans: Refer 1.2.(a) 3. List four non-linear resistors. [W-07] [2 M] OR State types of non-linear resistors. [S-09] [2M] Ans: Refer Explain NTC and PTC resistors with temperature resistance characteristics. [W-07, 13; S-14] [4 M] Ans: Refer 1.7.(b) 5. State the meaning of wattage with reference to resistor. [S-08] [2 M] Ans: Refer 1.2.(a) 6. Give two specifications of carbon film resistor. [S-08] [2 M] Ans: Refer 1.5.(b) 7. Draw constructional details of carbon film and wire wound resistor and explain. [S-08] [4 M] Ans: Refer 1.5.(b) and 1.5.(c) 8. List any two specifications of resistors. [W-08] [2 M] Ans: Refer 1.2.(a) 9. Draw construction of LDR and name different parts. [S-09] [2 M] Ans: Refer 1.7.(a) Basic Physics (F.Y.Dip.Sem.-1) Chapter 01: Resistors MSBTE 10. Compare TDR and LDR on the basis of working principle, materials used for construction, characteristics and application. [S-09] [4 M] Ans: Refer 1.7.(c) 11. Define tolerance of resistor. [W-10] [2 M] Ans: Refer 1.2.(a) 12. Draw constructional diagram and label various parts of carbon film resistor. [W-10] [2 M] Ans: Refer 1.5.(b) 13. Compare linear and logarithmic potentiometer on the basis of relationship between resistance and rotation of shaft and resistivity. [W-10] [2 M] Ans: Refer 1.6.(e) 14. Draw constructional details of LDR with suitable label, explain its operation. State its application. [W-10] [4 M] Ans: Refer 1.7.(a) 15. Define: i. Active component ii. Passive component iii. Discrete component iv. Non discrete component and give one example for each [S-11] [4 M] Ans: Refer Draw a labelled diagram of Light Dependent Resistor (LDR) and explain the concept how variation of light will change the resistance. [S-11] [4 M] Ans: Refer 1.7.(a) 17. Draw and describe the construction of LDR. List its two applications. [S-13] [4 M] OR Describe the working of LDR with neat sketch and list applications of it. [S-15] [4 M] Ans: Refer 1.7.(a) 21

29 Target Publications Pvt. Ltd. 18. List specifications of resistor. State any two. [S-13] [4 M] OR List specifications of resistors and explain any two. [W-15] [4 M] Ans: Refer 1.2.(a) 19. List two applications of LDR. [S-14] [2 M] Ans: Refer 1.7.(a) 20. Explain the working of TDR along with its symbol and characteristics. [W-14] [4 M] Ans: Refer 1.7.(b) 21. List the specifications of linear and nonlinear potentiometers. State its applications (Four points). [W-14, 15] [4 M] Ans: Refer 1.6.(d) 22. Compare linear and logarithmic potentiometers. (any four points) [S-15] [4 M] Ans: Refer 1.6.(e) 22 MSBTE Numericals 1. Write colour code of 1 k resistor. [W-15] [2 M] Solution: Given: Value of resistance = 1 k = 1000 To find: Colour of the bands in order Formula: Value of resistance = xy 10 z T% Value of resistance = 1000 = Comparing this with the formula, Here, x = 1, y = 0, z = 2 Referring to colour code table, The first ring/colour for x = 1 is brown. The second ring/colour for y = 0 is black, The third ring/colour for z = 2 is red. Ans: The colour of the bands of the resistor are Brown Black Red. Elements of Electronics (F.Y.Dip.Sem.-2) (Electronics) MSBTE 2. Give the colour code for the following resistors. i. 100, 10 % ii. 47 k, 5 % [S-08] [2 M] Solution: i. Given: Value of resistance = 100, 10 % To find: Colour of the bands in order Formula: Value of resistance = xy 10 z T% Value of resistance = % Comparing this with the formula, Here, 100=10 10 x = 1, y = 0, z = 1 Referring to colour code table, The first ring/colour for x = 1 is brown. The second ring/colour for y = 0 is black, The third ring/colour for z = 1 is brown. The fourth ring/colour for T = 10% is silver. Ans: The colour of the bands of the resistor are Brown Black Brown Silver. ii. Given: Value of resistance = 47 k, 5 % To find: Colour of the bands in order Formula: Value of resistance = xy 10 z T% Value of resistance = 47 k 5 % = % Comparing this with the formula, Here, x = 4, y = 7, z = 3 Referring to colour code table, The first ring/colour for x = 4 is yellow. The second ring/colour for y = 7 is violet. The third ring/colour for z = 3 is red. The fourth ring/colour for T = 5% is gold. Ans: The colour of the bands of the resistor are Yellow Violet Red Gold. 3. Give colour code for the following resistor: 560 k, 2% [S-10] [2 M] Solution: Given: Value of resistance =560 kω ±2% To find: Colour of the bands in order

30 Target Publications Pvt. Ltd. Formula: Value of resistance = xy 10 z T% Value of resistance = 560 kω 2 % = % Comparing this with the formula, Here, x = 5, y = 6, z = 4 Referring to colour code table, The first ring/colour for x = 5 is green. The second ring/colour for y = 6 is blue. The third ring/colour for z = 4 is yellow. The fourth ring/colour for T = 2% is red. Ans: Colour code for 560 k 2 % is Green- Blue-Yellow-Red. 4. Write colour codes for following resistors. i. 470 k ± 5% ii. 1.2 M ± 10%. [S-14] [4 M] Solution: i. Given: Value of resistance = 470 kω ±5% To find: Colour of the bands in order Formula: Value of resistance = xy 10 z T% Value of resistance = 470 kω 5 % = % Comparing this with the formula, Here, x = 4, y = 7, z = 4 Referring to colour code table, The first ring/colour for x = 4 is yellow. The second ring/colour for y = 7 is violet. The third ring/colour for z = 4 is yellow. The fourth ring/colour for T = 5% is gold. Ans: Colour bands on the given resistor are Yellow Violet Yellow Gold. ii. Given: Value of resistance = (1.2 M ± 10%) To find: Colour of the bands in order Formula: Value of resistance = xy 10 z T% Basic Physics (F.Y.Dip.Sem.-1) Chapter 01: Resistors MSBTE Value of resistance = (1.2 M ± 10%) = % = % Comparing this with the formula, here x = 1, y = 2, z = 5, T = 10% Referring to colour code table, The first ring/colour for x = 1 is brown. The second ring/colour for y = 2 is red. The third ring/colour for z = 5 is green. The fourth ring/colour for T = 10% is silver. Ans: Colour bands on the given resistor are Brown Red Green Silver. 5. Using colour code, write the colour codes for the following resistors i. 680 kω, ± 5% ii. 3.3 Ω, ± 10% [W-14, 15] [4 M] Solution: i. Given: Value of resistance = 680 kω, ± 5% To find: Colour of the bands in order Formula: Value of resistance = xy 10 z T% Value of resistance = 680 kω 5 % = % Comparing this with the formula, Here, x = 6, y = 8, z = 4 Referring to colour code table, The first ring/colour for x = 6 is blue. The second ring/colour for y = 8 is grey. The third ring/colour for z = 4 is yellow. The fourth ring/colour for T = 5% is gold. Ans: Colour bands on the given resistor are Blue Grey Yellow Gold ii. Given: Value of resistance =(3.3 10%) To find: Colour of the bands in order Formula: Value of resistance = xy 10 z T% 23