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- Introduction of analog electronics
- Resistor and its connections
- Definition, property, unit
- Types of resistors
- Value of resistors with color coding and multimeter
- Current and voltage
- Definition, Unit and measuring devices
- Types of current sources (AC and DC)
- Use voltmeter and ammeter
- Ohm’s law and power
- Definition, unit and application
- Formula with practical
- Capacitor and inductor
- Capacitor’s definition, unit and property
- Types of capacitors
- Testing and charging and discharging of capacitor
- Inductor (coil)’s definition
- Types of inductors
- Definition and principle
- Types of transformer
- Losses of transformer
- Testing of transformer
- Definition and property
- Types of semiconductor
- P-n junction and its biasing
- Definition and construction
- Types of diodes
- Testing of diode
- Definition and property
- Types of transistor
- Function of transistor
- Configuration of transistor
- Testing of transistor
- Important symbols
- Test paper
1.Introduction of analog electronics
The branch of science and engineering, which deals with the flow of electrons through a vacuum or gas or semiconductor, is known as electronics.
Electronic device: -The device, which directly or indirectly run on D.C. is called electronic device.
Types of electronic components: -
- Passive components: - The electronic components, which are not capable of amplifying or processing an electrical signal, are called passive components such as resistors, capacitors, and inductors.
- Active components: - The electronic components which are capable of amplifying or processing an electrical signal are called active components such as vacuum tubes, gas tubes and semiconductor (solid state) devices.
Types of electronic signal: -
- Analog: - The electronic signal, which has variation. These accept signal and represent in signal. These signals are in sine wave form and travel between several points (value).
- Digital: - These are signals, which has accurate value of fix result. It has only two types of value high (1) or low (0). It accept alphabet and number as input. It accepts signal and digit both but represent in digit only.
0 1 2 3 4 5
There are two types of electronic components: -
1. Active components: - The electronic components, which are capable of amplifying or processing an electrical signal, are called active components such as diode, transistor, Ics etc.
2. Passive components: - The electronic components which are not capable of amplifying or processing an electrical signal are called passive components such as resistors, capacitors, transformers, inductors etc.
The instruments in which electronic devices are employed for measuring various electrical quantities such as voltage, current, resistance, frequency are known as electronic instruments.
Multimeter: -This instrument can make many measurements with reasonable accuracy such as a.c. and d.c. Voltage, current, resistance etc. Since it is a miliammeter, voltmeter and ohmmeter combined so it is called AVO meter.
Cathode ray oscilloscope (CRO): - It gives a visual indication of a signal waveform. It is used for trouble shooting in radio and television. It can measure voltage, amplitude, frequency and phase shift.
Signal generator: - electronic equipment used to generate a waveform of known shape and frequency is known as signal generator.
- RESISTORS AND ITS CONNECTIONS
[IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image003.gif[/IMG]Definition-It is the component, which is used to limit the amount of current or provide the voltage, and its ability of resistor is to oppose the flow of current is called resistance. It is made of metal film oxide, carbon oxide, ceramic materials etc.
[IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image004.gif[/IMG][IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image005.gif[/IMG]Symbol: Or Tolerance
[IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image006.gif[/IMG][IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image006.gif[/IMG][IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image006.gif[/IMG]Denoted by: “R”
Measuring unit: “W” (Ohm)
First significance digit Second significance digit
Resistance: - It is the property of a resistor due to which it opposes the flow of current. The length, cross-sectional area and resistivity of the material determine resistance. “R” denotes it.
Conductance: - The ease with which a substance allow current to flow is called conductance and it is reciprocal of resistance. “G” denotes it.
Measuring unit – mho
\G = [IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image008.gif[/IMG]
Tolerance: - The first three-color bands of a resistor indicate the initial value and the fourth represent the tolerance rating. If a resistor, which is 100 W + 5%, it means the value of resistor can varied from 95W to 105W.
Table of color-coding of a resistor:
Resistor color coding Color 1st Band 2nd Band 3rd Band Tolerance B Black 0 0 100 + 1 % B Brown 1 1 101 + 2 % R Red 2 2 102 + 3 % O Orange 3 3 103 + 4 % Y Yellow 4 4 104 - Great Green 5 5 105 - Britain Blue 6 6 106 - Very Violet 7 7 107 - Good Grey 8 8 108 - Wife White 9 9 109 - Gold - - 10-1 + 5 % Silver - - 10-2 + 10 % No color - - 10-3 + 20 %
Rules for color-coding:
- Black, Gold, Silver and No Color is never comes in 1st Band.
- Gold and Silver always comes after 2nd Band.
- Always gap between 3rd and 4th Band.
- Any resistor has minimum 3 colors and maximum 6 colors.
- Sixth band shows power rating of resistor.
- Sixth band contains only two colors Brown for 1watt and Red for 2watt
Types of Resistors:
From the operating condition point of view the resistor may be fixed resistor and variable resistor.
- Fixed resistor: - The resistor, which have fixed value of resistance, are called fixed resistor. They may be carbon composition or wire wound resistor.
- Carbon composition resistor: - Most common in electronic circuit are carbon composition resistor with a low power rating (2 W or less). This type of resistor is made of mixture of carbon or graphite and clay. The two materials are mixed in proportions needed for the desire value of resistance. The resistor element is enclosed in a plastic case as shown in figure below for insulation and mechanical strength. The leads are made of resistance element.
[IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image009.gif[/IMG][IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image010.gif[/IMG] ¼ W
They are made of carbon (a conductor) and clay (a non conductor), which is pressed and moulded into rods by heating. Its value ranges from a few ohms to 10-mega ohm. A typical tolerance is + 10% and ratings are from 0.125 W to 1 W. Although their stability are poor, they are cheap but noisy used in loudspeaker of audio equipment.
- Deposited film: - A film of carbon is deposited on a ceramic rod and protected by a tough insulating coating. Value rating and cost are similar to the carbon composition type but tolerance are better (e.g. + 5%) and stability very good.
- [IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image014.gif[/IMG]Metal oxide: - These offer high stability over long period of time. Tolerance is +3 % and rating typically 0.5 W. Their construction and appearance is similar to the carbon films type tin oxide replacing carbon.
- Wire wound resistor: - A wore wound resistor construction, a resistance wire (nicrome = nickel and chromium), tungsten, or managain is wrapped around a hollow cylindrical core. The ends of the wire are attached to metal pieces fixed at the two or three ends of the core. This assembly is coated with enamel containing powdered glass and is heated which is developed the coating known as vitreous enamel. The hard and smooth coating provides mechanical protection to the resistance wire. It also helps in dissipating heat away from the unit quickly.
Wire wound resistor
The value of resistance depends upon the resistivity of the material used and the dimension (length and cross sectional area) of the resistance of the wire. These resistors are readily available in value of ranging from 1 W to 100 KW and more. The power rating of these resistors varies from 2 W to 500 W.
- Variable resistor: - Some times in electronic circuit it becomes very necessary to adjust (control) the value of current and voltage. For example to change the volume of sound in transistor, radio and television to adjust the brightness and contrast of the TV picture etc.
These adjustments can be made with the help of variable resistor. The variable resistor may be carbon composition or wire wound resistor. The internal construction of the resistor is a thin carbon coating on pressed paper or a molded carbon disk constitutes the carbon composition resistance element. The two ends of the disk are joined to the external soldering lugs. The middle terminal is connected to the variable arm that contract the resistor element by a metal spring wiper as the shaft of the control is turned, the variable arm moves the wiper to make contact at different points on the resistor element which changes the value of resistance inserted in the circuit.
Variable resistors are used as volume and other control in the radio and television sets are usually called pots they consists of incomplete circular track of either fixed carbon for high value and low power (up to 20 W) or a fixed wire wound resistor for high power. The value varies from few ohms to several mega-ohm. Common values are 1 KW, 10 KW, 50 KW, 100 KW, 500 KW and 1 MW.
[IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image016.gif[/IMG] [IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image017.gif[/IMG] [IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image018.gif[/IMG]
There are two ways of using variable resistor. It may be used as a preset to control the current in the circuit. It can also act as a potential divider to obtain any voltage from 0 to maximum voltage to supply by rotating the spindle (clockwise).
Type of variable resistor: - The variable resistor can be either linear or non linear.
- Linear: - In the linear type the former over which wire is wound is of uniform height. That is why the value of resistance varies linearly with the rotation of moving contract.
- Non - Linear (Log): - In non-linear type the former has non-uniform height that is why the value of resistance varies non-linearly. These resistors are mostly used as volume control in sound equipment.
According to power rating there are four types of resistor.
- Low power resistor: - Resistor, which can work on maximum 2 W power, are called low power resistor.
Features: - Value defined by printed code, Small in size, Carbon metal composition, Work on low current. Only two legs, comes in five types.
- High power resistor: - It works on above 2 W power rating.
Features: - No color coding, Value defined by printed code, Bigger in size, Two or more than two legs, wire wound only, work on high current and voltage, For dissipating the heat holes on its body.
- Special resistor: -
- [IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image021.gif[/IMG]LDR (Light dependent resistor): - Its value depends upon light. If there is light it will produce high resistance. If there is dark then it will produce no resistance. Example – emergency light, streetlight.
- [IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image022.gif[/IMG]VDR (Voltage dependent resistor): - Its value depends upon voltage. If there is voltage it will produce high resistance. If there is low voltage it will produce low resistance. It is used in voltage regulator.
- TDR (Temperature dependent resistor): - Its value depends upon temperature. It may be used as NTC (negative temperature coefficient) or PTC (positive temperature coefficient). It is also known as thermister denoted by TH. NTC used in AC and fridge and PTC used in automatic press (iron).
Difference between preset and pots Preset Pots 1. Used in inner panel. 1. Used in front panel. 2. For technician only. 2. For user also 3. Less option. 3. More option. 4. Used for control the current in circuit. 4. Used as potential or voltage divider. 5. Small in size. 5. Bigger in size.
Standard resistors: -
International Association of Electronics Value of resistance in W Value of resistance in KW Value of resistance in MW 1.0 10 100 1.0 10 100 1.0 10 1.2 12 120 1.2 12 120 1.2 12 1.5 15 150 1.5 15 150 1.5 15 1.8 18 180 1.8 18 180 1.8 18 2.2 22 220 2.2 22 220 2.2 22 2.7 27 270 2.7 27 270 2.7 3.3 33 330 3.3 33 330 3.3 3.9 39 390 3.9 39 390 3.9 4.7 47 470 4.7 47 470 4.7 5.6 56 560 5.6 56 560 5.6 6.8 68 680 6.8 68 680 6.8 8.6 86 860 8.6 86 860 8.6
Note- 1. The types of resistor are mainly available in value ranging from 1W to 22 MW.
- Each resistor has two main characteristics i.e. its resistance are in W and its power rating in W
Testing of Resistor: -
Low power resistor – When testing of multimeter the meter show value including tolerance.
High power resistor – Written value check out by multimeter including tolerance
Variable resistor – While testing in multimeter putting probe in side leg the multimeter show the accurate value of resistor and it should vary when one probe is placed on the middle leg according to the movement of knob.
OK Condition – When multimeter show deflection but not full then it is OK.
Faulty Condition – It may be either short or open.
Short condition – When positive or negative meets together. In this case multimeter show full deflection.
Open condition – When the path is break. In this case multimeter show no deflection.
Connection of Resistor: -
Series connection - When two or more resistors are connected to each other serially then it is said to be series connection and total resistance always greater than individual resistance.
R = R1 + R2 + R3
Parallel connection – When all the resistors are connected parallel to other it is said to be parallel connection.
Mesh connection – The combination of series and parallel connection is known as mesh connection.
E R K M J K M W W KW MW + 5% + 10% + 20%
- A resistor has a color band sequence green, blue, orange, and gold. Find the range in which its value must les depending upon the manufacturer’s tolerance to suit a circuit. Ans: 58.8 ohm, 53.2 ohm
- A resistor has a color band sequence yellow, violet, orange and silver. Find the range in which its value must lie so as to satisfy the manufacturer’s tolerance.
Ans: 51.7 ohm, 42.3 ohm
- A resistor has a color band sequence orange, orange, gold and gold. Find the range in which its value lies so as to satisfy the tolerance. Ans: 3.465 ohm, 3.135 ohm
- A resistor has a color band sequence red, red and blue. Find the range in which its value must lie so as to satisfy the manufacturer’s tolerance. Ans: 26.4 ohm, 17.6 ohm
- A resistor has color band sequence blue, gray, yellow and silver. Find the range in which its value must lie depending upon the manufacturer’s tolerance to suit your circuit. Ans: 612 - 748 k-ohm.
- A resistor has color band sequence brown, black, green and gold. Find the range in which its value must lie so as to satisfy the manufacturer’s tolerance.
Ans: 0.95 M-ohm-1.05 M-ohm.
- The average value of a resistor is 33 k-ohm. What will be the sequence of the color bands? The tolerance may be considered as 5 %. Ans: Orange, orange, orange, gold.
- CURRENT AND VOLTAGE
Current source: - When the value of load resistance is very small as compared to the internal resistance of the source. It is treated as current source.
Current: - Flow of electron or negative charge is called current.
Unit – ampere (A)
Measuring device – ammeter (Connected in series to the circuit)
Voltage source: - When the value of load resistance is very large as compare to the internal resistance of the source. Then the source is treated as voltage source.
Voltage: - Voltage is the force, which tends to move electron from one terminal to another terminal.
Unit – volt (v)
Measuring device – Voltmeter (Connected in parallel or across to the circuit)
Voltage rise: - Energy introduce into the circuit by a voltage source is called voltage rise. “VR” denotes it.
Voltage drop: - Energy remove from the circuit by load is called voltage drop. “VD” represents it.
KVL (Kirchoff’s voltage Law): - According to KVL law the sum of voltage rise is always equal to the sum of voltage drop in any closed circuit.
R = R1+R2 V = IR, V1 =IR1, and V2 = IR2
V = V1 + V2
KCL (Kirchoff’s current Law): - According to KCL law the sum of incoming current is always equal to outgoing current in any closed circuit.
[IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image030.gif[/IMG] And [IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image032.gif[/IMG]
I = I1+ I2
Internal resistance and Impedance
- Internal Resistance: - The opposition to load current inside the D.C. source is called its internal resistance. All D.C. sources have internal resistance and RI represents it. The voltage across the load terminal is reduced because of the voltage drop in the internal resistance.
When load (RL) is connected across the source
[IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image033.gif[/IMG]Load current, [IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image035.gif[/IMG] Ri
Terminal Voltage, [IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image037.gif[/IMG] RL
- Impedance: - The opposition to the load current outside the D.C. source is called its internal impedance. It is denoted by ZI.
When load (ZL) is connected across the source
[IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image043.gif[/IMG]Load current, [IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image045.gif[/IMG] Zi ZL
Terminal voltage, [IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image047.gif[/IMG] E
Power (W) = VI = [IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image049.gif[/IMG]
Types of material
- Conductor - Material in which electron freely moves on it is called conductor. Ex- copper, aluminum, iron etc. In conductor resistance is very low.
- Insulator- Material in which electron does not moves freely is called insulator. i.e. plastic, wood etc. In insulator resistance is very high.
Source of electrical power
For any electronic circuit to work, a source of electrical power is required. The basic purpose of a source is to supply power to load. The source may be either DC or AC.
- [IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image050.gif[/IMG]DC source: - The terminology of DC stands for any quantity i.e. steady (constant) and unidirectional in nature.
- [IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image054.gif[/IMG]AC source: - The terminology of AC stands for any quantity that changes in magnitude and direction.
Any device that produces direct voltage output continuously is called a d.c. source.
- Battery: - A battery is most common DC voltage source used in the electronic circuit. A battery is just a series of parallel or series combination of primary or secondary cells. The secondary cells are rechargeable where as primary cells are not. The battery used in automobiles contains number of secondary cells in series where as dry cells used in torches are primary cells.
- Solar cell: - Solar cell convert light energy into electrical energy. These are also used for operation of electronic circuit i.e. calculator. These cells are used where small powers are required.
- Generator: - A DC generator is an electrical machine, which convert mechanical energy into electrical energy. When armature is rotated by prime mover (water turbine, steam turbine) in the stationary magnetic field. The required DC voltage appears across its terminals. DC generators are used where large power is required.
- Rectifier type sources: - It consists of a step down transformer and rectifier to obtained required output DC voltage. The supply used most frequently in the electronic laboratory.
Any device that produces alternating voltage output continuously is called a.c. source.
- Alternator: - An AC generator is known as alternator. It is a similar machine as that of DC generator. The only difference is that its output is AC voltage instead of DC voltage. These machines are installed at the generating stations where power is generated at 50 Hz. This power is applied to various electronic circuits.
- Oscillators or signal generator: - An oscillator or signal generator is the equipment, which supplies AC voltage at different frequency. Its output is used to test the working of various electronic circuits, i.e. Amplifier
- A lead acid battery fitted in an automobile has and emf of 24 volts and has an internal resistance of 0.05 ohm. It supplies a total load of 100 watt. Find (a) load current (b) voltage drop in internal resistance and (c) terminal voltage. Ans- 4.167A, 0.02V, 23.8 V.
- A D.C. source generating 250 V has an internal resistance of 1000 ohm. Find the load current if load resistance is (1) 20 ohm (2) 60-ohm and (3) 100 ohm. Ans 0.2451 A, 0.2358 A, 0.2272 A
- A lead acid battery of emf 12 V has an internal resistance of 5 ohm. Find the output current if load is (i) 100 ohm (ii) 15 ohm (iii) 3 ohm (iv) 1 ohm. Ans 0.11 A, 0.6 A, 1.5 A, 2 A.
- A lead acid battery of emf 12 V has an internal resistance of 0.05 ohm. It supplies a total load of 80 watts when fitted in an automobile. Determine (i) load current, (ii) voltage drop in internal resistance (iii) terminal voltage. Ans 6.67 A, 0.33 V, 11.67 V.
- A D.C. source is generating 200 V and its internal resistance is 800 ohm. Find the load current if load resistance is (i) 20 ohm (ii) 100 ohm and (iii) 200 ohm. Ans 0.2439 A, 0.2222 A, 0.2 A.
4. OHM’S LAW AND POWER
Ohm’s Law: - According to ohm’s law in any electrical circuit resistance is constant. If we can increase the voltage then current is also increased but if voltage is constant and we will increase the resistance then current will decrease.
So we can say current is directly proportional to voltage but inversely proportional to resistance.
Power: -The rate at which work done is called power. It refers to the amount of work done is specific length of time. It is directly proportional to both voltage and current. So we can say it is product of voltage and current.
Unit: - Watt (W)
Power = voltage ´ current
(Watt = volt ´ ampere)
W =V ´ I = [IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image049.gif[/IMG]
[IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image056.gif[/IMG][IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image057.gif[/IMG]The two conducting plates separated by an insulating material (called dielectric) form a capacitor. The basic purpose of a capacitor is to store charge. The capacity of a capacitor is to store charge per unit potential difference is called its capacitance. “C” represents it.
The unit of capacitance is Farads (F). This unit is too large; the capacitors are specified practically microfarads (mF) and Pico farads (pf).
The usual function of the capacitor is to block the D.C. voltage but pass the A.C signal voltage. By means of charging and discharging this application include coupling by passing and filtering the A.C. signal. So we can say it is a component, which after low impendence to A.C. but very high impendence to D.C.
Property of capacitor: -
Lower the frequency higher the reactance and higher the frequency lower the reactance.
Types of capacitor
- Polarized Capacitor: - The Capacitor, which has distinct polarity, is called polarized capacitor. There are two types of polarized capacitor.
- Electrolytic capacitor: - An electrolytic capacitor contains two aluminum electrodes between the two electrodes absorbent gauge soaks of electrolyte (borax, phosphate, carbonate). To provide the required electrolysis produces an oxide film at the positive electrodes when D.C. voltage is applied.
The oxide film acts as an insulator and forms a capacitance between the positive aluminum electrode and the electrolyte in the gauge separator. The negative aluminum electrode simply provide a connection to the electrolytes usually the metal can itself act as the negative terminal of the capacitor.
Electrolytic capacitors have a high capacitance to sized ratio. Since the Al2O3 layer is molecular thin, these capacitances are variable in capacitance value ranges from 1mf to 10000mf or more. The common voltage ratings are from 1 volt to 700 volts. The leakage current of these capacitors is as high as 0.12-mA/mf to 0.5-mA/mf. These capacitors are commonly used in situation where large capacitance is required. Generally these capacitors are used in filter section of D.C. power supply and transistor circuit.
[IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image058.gif[/IMG]These capacitors must be connected in circuit as per polarity marked on the capacitor. If they are connected in opposite polarity the reversed electrolysis forms gas in the capacitor. It becomes hot and may explode.
Features of electrolytic capacitor: -
- Cylindrical in shape.
- Value above 1mf.
- It has distinct polarity (positive and negative).
- Negative sign marked on that capacitor.
- Tantalum capacitor: - Tantalum is used is used instead of aluminum. The size of tantalum capacitor is very small but capacitance is same since the dielectric constant for tantalum oxide is 25 times as compared to dielectric constant of 7 for Al2O3. The other important features of this capacitor are that they have longer life and less leakage current.
- Non-polarized capacitor: - The capacitor is only made by dielectric material. There are no required polarities. The commercial capacitors are generally classified according to the dielectric. Some of the most commonly used capacitor is paper, mica, ceramic, and polyester etc.
[IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image061.gif[/IMG]Features of non-polarized capacitors: -
- [IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image062.gif[/IMG]No polarity.
- Mostly used to pass A.C. current.
- Cannot check by multimeter.
- When 100% pass A.C. that means OK.
- Value below 1 mf.
Temperature coefficient Voltage D.C. Unit Color Value Brown 100 volts 1 pf = 10 –12 f Black -10 ´ 10-6 Red 250 volts 1 mf = 10 –6 f Orange -150 ´ 10-6 Yellow 400 volts 10 K = 10 Kpf =10000 pf Violet -750 ´ 10-6 Blue 630 volts 104 = 100000 pf = 100 Kpf
Trouble in Capacitor: -
A capacitor may be open or short-circuited. In both cases the capacitor is useless. Since it cannot store the charge sometimes a capacitor may be partially short circuit (leaky capacitor). In normal service usually capacitors can become short circuited because the dielectric detariates with age which remains under the stress of charging voltage.
Higher temperature also produces adverse effect. The capacitors may leaky gradually. Ultimately the dielectric may puncture and cause sort circuit. The effect is more common with paper and electrolytic capacitor.
There is every possibility of open connections in any type of capacitor causing open circuit fault. In addition to this in case of electrolytic capacitors high resistance is developed in the electrolytes with age. Particularly at high temperature sometimes after a few year electrolyte may dry up causing high resistance (capacitor is partially open).
In such cases much of capacitor action is gone and the capacitor has to be replace. When the capacitor is in good condition. It has high resistance in the order of mega ohms. A short circuit capacitor has zero ohm resistance and continuity. Whereas the resistance of leaky capacitor is lower than normal. A capacitor can be checked with an ohmmeter.
Checking of capacitor with an Ohmmeter: -
For checking of a capacitor the highest range such as (mega ohm) is selected. One side of capacitor is disconnected from the electric circuit to eliminate any parallel resistance path that can lower the resistance. Keep your finger off the connections otherwise your body resistance will lower the readings.
The Ohmmeter leads are connected across the capacitor is sure before connecting the leads of the ohmmeter across the capacitor that the capacitor is discharge. For a good capacitor, the meter points moves quickly towards the low resistance side of the scale and then slowly recedes back towards the high resistance side.
It is because as soon as the leads are connected across the capacitor. The capacitor start charging by the battery of ohmmeter itself therefore at the first instant maximum current flows and the pointer rises quickly towards zero resistance side. Then the charging current decrease as the capacitor voltage increases towards the applied voltage of the battery of ohmmeter hence the needle recedes towards the high resistance. Note that the charging of the capacitor causes both rise and fall of the needle.
The capacitor is not discharges at all however if it is required to discharge the meter leads are reversed or the capacitor terminal are short-circuited. The reading when the pointer stops moving is the insulation of the capacitor, which is normally very high.
The troubles in a capacitor as per the ohmmeter reading are indicated as follows: -
- If the needle of the ohmmeter rises immediately to zero and stays there the capacitor is short-circuited since the current flows through the circuit continuously.
- If the needle of the ohmmeter rises quickly and then recedes back but the final resistance reading is appreciably less than infinitive the capacitor is leaky. Such capacitors are particularly troublesome in high resistance circuit.
- If the needle of the ohmmeter does not rise and stays at infinitive resistance value the capacitor may be open. However since very high resistance is normal condition for a capacitor. Be sure that capacitor was discharge properly before checking. It will be better to discharge the capacitor again and once more check.
The electronic component, which opposes the charge of current in circuit, is called an inductor. The ability of coil or inductor due to which it opposes the change of current flowing through it is known as its inductance. The inductance of an inductor may also be defined as the ability of an inductor to produce induced voltage when then current varies through it.
[IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image063.gif[/IMG]The unit of inductance is hennery, which is named after Joseph Hennery. “L” denotes it. Symbol:
Function of coil: -
An inductor is a component, which offer high impedance to A.C. but very low impedance to D.C.
Property of coil: -
- Coil has opposite effect of capacitor.
- Higher the frequency (A.C.) higher the reactance. The usual function of an inductor in the electronic circuit is to block the A.C. signal but pass the D.C signal.
Difference between capacitor and Inductor: -
Alternating Current Direct Current. Capacitor Pass the current. Block the current. Inductor Block the current. Pass the current
Coil: - When any metallic wire wrapped or wound around an object is called coil. The object is known as core.
Principal of Coil: -
- When A.C. passes through a coil it produces magnetic field.
- When magnet is rubbed over a coil then it induces current.
- An area occupied by electric line of force is called electric field. In a wire where it is more electric field. The pole is known as South Pole and another is North Pole.
Use of coil: -
It is used to filter the electronic or electrical signal and to drop the voltage and delay the current and so on.
Types of filter circuits: -
There are two types of filter circuit used in electronic circuit. 1. I/P High frequency
2. I/P Low frequency
Types of Inductor: -
- Fixed inductor: -
- Filter chokes: A filter choke is an inductor used in filter section of D.C. power supply. A typical filter choke has many turns of wire wound on an iron core.
- Radio frequency chokes: Radio frequency choke is smaller in size as compared to filter chokes. Air core coil for RF applications have very small value of inductance. For example an RF coil for the radio broadcast band of 535 to 1605 KHz may have an inductance of 250 mH or 0.5 mH.
- Variable inductor: -Variable inductors are used in tuning circuit for radio frequency. The winding is placed over a fiber or ceramic former and to change the inductance.
Inductive reactance: -
The C.E.M.F. (current electro magnetic field) is including into an inductor by a very fixed current to oppose the applied voltage. As a result the total effective voltage in the circuit is the difference between the applied voltage and introduce voltage because the introduce voltage is less than the applied voltage. The effect of the inductance is to minimize or reduce current flow. Greater inductance is the greater the C.E.M.F. The opposition of current flow by an inductor in an AC circuit is applied inductance reactance.
It is measure in ohm.
X = 2F´L, where F =frequency, L = inductance and X = reactance.
Use of coil: -Used in printer head, motherboard, SMPS, and monitor.
Testing of coil: - Coil should be show deflection either full or half depending upon the length and diameter of coil.
- OK condition: - If meter show deflection but not full.
- Open condition: - No deflection.
- Short condition: - Full deflection.
A transformer is just similar to appearance to an inductor or filter chock. It consists of inductor having the same core in the coil to which supply is connected called primary winding. The coil which load is connected is called secondary winding. When an A.C. supply is applied to the primary winding an emf is induced in the secondary side.
Thus the transformer is a static device, which transfers power from one circuit to another circuit depending upon the number of turns on secondary and primary side. A transformer may be step up (secondary turn > primary turn) or step down (secondary turn < primary turn) more turn more supply and less turn less supply and also by the multimeter more turn more resistance less turn less resistance.
Principle of Transformer: -
The principle on which the transformer action is based is called electro magnetic field mutual induction (EMI). When current is a flow through a conductor a magnetic field build up around the conductor. If A.C. is used the magnetic field collapses builds again for each cycle of the applied current and another conductor placed in this moving magnetic field will how an EMF included into it.
Thus Transformer is a device, which transfer the electronic signal from one region to another without changing the frequency.
Co-efficient of coupling: -
The amount of emf into secondary winding depends upon the degree of flux linkage between the two points. The percentage of primary flux lines which cuts the secondary winding is also called as co-efficient of coupling lies between 0 and 1. When all the primary flux lines cut the secondary coil the co-efficient of coupling is 1. When no flux line cut the secondary coils the co-efficient of coupling is 0.
Difference between primary and secondary coil: -
Primary coil Secondary coil 1. Less deflection. 1. More deflection. 2. High resistance. 2. Low resistance. 3. Thinner wire. 3. Thicker wire. 4. More gaps between primary coil. 4. Less gap between secondary coils. 5. Red and white insulator. 5. Used other colors.
Types of transformer: -
- Step up transformer: -Step up transformer consist of two coils wound on the same core the coil to which the input voltage is applied is called primary winding and the other coil in which voltage is include due to changing flux are called secondary winding.
[IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image064.gif[/IMG]In step up transformer secondary winding is more than primary winding. In this transformer input voltage applied low and output induced high voltage.
Transformer ratio: - NP > NP , ratio = [IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image066.gif[/IMG]
Output voltage = [IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image068.gif[/IMG]voltage
- Step down transformer: -In step down transformer primary winding is more than secondary winding. In this transformer input voltage applied high and output voltage induced low due to changing magnetic flux and because of number of turns in secondary coil is less than primary coil.
[IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image069.gif[/IMG]Transformer ratio: - NP > NS, ratio =[IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image066.gif[/IMG]
Voltage ratio: - Voltage is directly proportional to turns of transformer. If we increase the number of turns then voltage will also increase and if we decrease the number turns voltage will also decrease.
According to ohm’s law,
For step down transformer, [IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image073.gif[/IMG]
For step up transformer [IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image075.gif[/IMG]
Current ratio: -Current is inversely proportional to number of turns. If we increase the number of turns current will decrease and if we decrease the number of turns current will increase.
Power ratio, PP = PS Þ VP ´ IP = VS ´ IS
A transformer that works for voltage in step up condition current is in step down and when a transformer works for voltage step down in that position current is step up.
[IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image078.gif[/IMG]Main transformer: - It is the transformer, which gives variable voltage with the signal input. It gives the multi outputs because in the output will have attach tap coil at several place and get such multi output of different voltages.
Types of transformer: -
- [IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image079.gif[/IMG]Single winding transformer: - In these transformer two tags in primary winding and two tags in secondary winding.
- [IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image080.gif[/IMG]Double winding transformer (Center tapped transformer): - In these transformer two tags in primary winding and three tags in secondary winding. In three tags middle tag is common. We can take two different outputs from transformer.
- [IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image081.gif[/IMG]L – winding transformer: - It is combination of single winding transformer and double winding transformer. Single winding
- SM – transformer (Switch mode transformer): - The transformer in your SMPS it has two tags in input and six tags in output. It provides three different voltages 12 V, 12 V and 5 V. High voltage DC 0
- Core losses: - When A.C. flows to winding; a changing magnetic field is established in the core. As this field expands and construct it induced a voltage into the core. The induced EMF causes eddy current to flow. The eddy current produced a power loss, which is equal to I2R. If eddy current could be reduced the power loss could be produced also. Thus laminating the core could reduce eddy current.
- Hystersis loss: - When iron is not magnetized its magnetic domains are arranged in random pattern. However if a magnetizing force is applied the domains line-up with magnetic field. When magnetic field reverse the domains must reverse their direction. In a transformer the magnetic field will reverse their direction many times in each second with the applied A.C. signal. In reversing direction again and again the transformer has to be do some work. The power dissipate in the form of heat is referred to as Hystersis loss. These losses can be reduced if metal called silicon steel is used instead of iron.
- Copper loss: -These losses are caused by A.C. resistance of copper wire in primary and secondary winding as current flows through this resistance. Some power is dissipate in the form of heat. P = I2R can determine the amount of power. Increasing the size of the copper wire can reduce the copper loss.
- External loss: - As the magnetic field expands and contract around the transformer it often cuts the external conductor. If a current is introduced into the conductor some power is loosed from the transformer. These losses can be reduced if transformers are placed in a housing to prevent magnetic field from escaping.
Testing of transformer: -
To test the transformer set the multimeter on ohm scale. Take both probe of multimeter and touch on the one pair of transformer. But before checking the transformer is sure your capacitor may be discharge. If multimeter shows some resistance then transformer is OK. If multimeter shows ultra high reading that means one of the coil is missing.
Open condition: - When multimeter shows no any deflection that means transformer is open.
Short condition: - When multimeter shows full deflection that means transformer is short.
In pure condition semiconductor are insulators but when mix with the material, which has 4, valances shell its conductivity lies between conductor and insulator. The most commonly used semiconductors are Ge and Si, which have respectively 32 and 14 electrons.
Main points about semiconductor: -
- The resistivity of a semiconductor is less than insulator but more than conductor.
- Semiconductor have negative temperature co-efficient of resistance it means the resistance decreases with the rise in temperature and vice-versa.
- When suitable metallic impurities (like arsenic, gallium etc) are added to a semiconductor, it changes current conducting properties of the semiconductor.
Types of semiconductors
- Extrinsic semiconductor (Impure semiconductors): - A semiconductor to which an impurity at controlled rate is added to make it conductive is known as an extrinsic semiconductor.
- Intrinsic semiconductor (Pure semiconductors): - An extremely pure semiconductor is called intrinsic semiconductor.
Note- The process by which an impurity is added to a semiconductor is known as doping.
Type of extrinsic semiconductor: -
- N-type semiconductor: - When a pure semiconductor material is doped with a pentavalent element such as arsenic (atomic number 33) some of the atoms of tetravalent semiconductor replace by arsenic atoms is called n-type semiconductor.
Main points about n-type semiconductor: -
- A large number of free electrons are made available by the addition of pentavalent impurity.
- A minute quantity of free electrons is made available by the generation of holes electrons pair when thermal energy at room temperature is imparted to the semiconductor crystal. These electrons leave behind holes in the valence band.
- The number of free electrons provided by the pentavalent impurity is far exceeding the number of holes. It is due to this predominance of electrons over holes that material is called n-type semiconductor material.
- P-type semiconductor: - When a small amount of trivalent impurity is added to a pure semiconductor providing a large number of holes in it, the extrinsic semiconductor thus formed is known as p-type semiconductor.
Main points about p-type semiconductor: -
- A large number of holes are made available by the addition of trivalent impurity.
- A minute quantity of holes electrons pairs are formed at room temperature because of heat energy is imparted to the semiconductor crystal. The free electrons thus formed are lifted to conduction band leaving behind holes in the valence band.
- The number of holes provided by trivalent impurity is far exceeding the number of free electrons. It is due to this predominance of holes over electrons that the material is called p-type semiconductor material.
Difference between p-type and n-type semiconductor: -
P-type semiconductor N-type semiconductor Majority carriers of holes. Majority carriers of electrons. Holes due to impurity. Electrons due to impurity. Negative in mobile charge. Positive in mobile charge. Electrons and hole due to increase in temp. Holes and electrons due to increase in temp.
P-n junction: - When a p-type semiconductor is suitably joined to an n-type semiconductor, the contact surface so formed is called p-n junction.
8. SEMICONDUCTOR DIODE
[IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image084.gif[/IMG]A p-n junction is known as semiconductor diode. A diode is created by joining n-type and p-type semiconductor such diode are referred to as junction diode or crystal diode. When junction is formed mobile charges (electrons and holes) are attracted to each other and drift towards junction and fill holes in p-type material when free electrons and holes recombined.
Biasing: -When a p-n junction is connected across an electric supply (potential difference), the junction is said to be under biasing.
- Forward biasing: -When the positive terminal of D.C. source or battery is connected to p-type and negative terminal is connected to n-type semiconductor of a p-n junction, the junction is said to be in forward biasing. In forward biasing resistance is very low.
- Reverse biasing: - When the positive terminal of D.C. source or battery is connected to n-type and negative terminal is connected to p-type semiconductor of a p-n junction, the junction is said to be in reverse biasing. In reverse biasing resistance is very high.
Use of crystal diode in rectifier
Rectifier is a circuit, which convert the ac current into dc current. It is used in regulated power supply.
Transformer Rectifier (Diode) Filter (Capacitor) Regulator (Zener diode)
Types of rectifier: -
- Half-wave rectifier.
- Full-wave rectifier.
- Bridge rectifier.
- Half-wave rectifier: -When the half cycle comes diode is in forward bias. So the positive of the input signal is obtained at output but when negative cycle comes diode is reverse bias and does not pass the negative half cycle. Finally only positive half cycle are found at output.
AC supplies C
- Output voltage is half of input voltage. RL
- Output frequency is equal to input frequency.
- Output current flow for only half cycle of input frequency.
- [IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image087.gif[/IMG]Full-wave rectifier: - Full wave rectifier uses two diodes. When positive half cycle comes diode D1 is in forward bias D2 is in reverse bias so D1 passes the current. Now when negative half cycle comes D2 is in forward bias and D1 is in reverse bias so D2 passes the current .We see that direction and current both is same. Hence both half cycles found at output.
- Output voltage is ¼ of the input voltage.
- Output frequency is double of input frequency.
- Output current flow for both the half cycle of input.
- Bridge rectifier: - In bridge rectifier there are four diodes use. When positive half cycle comes D1 and D3 are in forward bias and D2 and D4 are in reverse bias. So the current passes through D1 and D3. For negative half cycle D2 and D4 are in forward direction and D1 and D3 are in reverse bias. Hence the current will flow through D2 and D4 which.
- Output voltage is half of input voltage.
- Output frequency is double of input frequency.
- Output current flow for both the half cycle of input current.
Output voltage = [IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image090.gif[/IMG]voltage
[IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image091.gif[/IMG]An ideal diode: - A diode is said to be an ideal diode when it acts like a perfect conductor (with zero voltage across it) when forward biased and like a perfect insulator (with zero current through it) when it is reverse biased.
Symbol: + –
An electronic circuit or device, which block the a.c. component but allows the d.c. component of the rectifier to pass the load is called a filter circuit. The main components used in the filter circuit are capacitor and inductor.
Types of filter circuit:-There are four types of filter circuit.
- Capacitor filter:- In this filter circuit a capacitor of large value is just connected across the output terminals of the rectifier with the load. The capacitor offers a low reactance path to a.c. component and allows it to pass through it but acts as an open circuit to d.c. components.
- In this filter circuit an inductor is just connected in series with the load. The inductor has the inherent property to oppose the change of current. This property of the inductor is utilized here to suppress the a.c. components (ripples) from the output of a rectifier.
- LC filter:- In this filter an inductor (choke) is connected in series and a capacitor is connected in parallel with the load.
- Pie filter:- In this filter an additional capacitor is connected in the beginning across the output terminals of the rectifier.
Types of diode: -
- R.F. diode: - Radio frequency diode work on very weak signal. It is mostly use for which signal coming from ratio and television antenna which signal is D.C. R.F. diode converts into D.C.
- [IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image096.gif[/IMG]It is very small in size and transparent.
- It is also called high frequency diode or signal diode.
- It is made up by glass and crystal. Symbol: -
- It is red in color.
- Normal diode: -
- Used in half wave, full wave and bridge rectifier.
- Its value less than 5A
- [IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image097.gif[/IMG]In concept it converts A.C into D.C.
- It is black in color.
- Symbol: -
- Power diode: - Features: -
- [IMG]file:///C:\DOCUME~1\ravi\LOCALS~1\Temp\msohtmlclip1\01\clip_image098.gif[/IMG]It is generally used where more than 5 A current is flowing.
- It looks like normal diode but size of diode is double than normal diode.
- Symbol: -