ENGINEERING PRACTICES LAB MANUAL

(Autonomous)

Affiliated to Anna University, Chennai

Approved by AICTE, Coimbatore-32

DEPARTMENT OF ELECTRICAL &ELECTRONICS ENGINEERING

LAB MANUAL

Course code/Course title : /Engineering Practices Laboratory

(Common to EEE,ECE,EIE,ETE)

Course/Branch : BE

Year/Semester : I/I

Regulation : 2015

ENGINEERING PRACTICES LAB MANUAL

SNO LIST OF EXPERIMENTS

1 STUDY OF ELECTRONIC COMPONENTS - RES IS TORS,

( CO L O R CO DI NG ) CAP ACI T O RS AND I NDU CT O RS

2 STUDY OF CRO (CATHODE RAY OSCILLOSCOPE)

3 SOLDERING OF S MALL ELECTRICAL AND ELECTRONIC CIRCUITS

4

SAFETY ASPECTS OF ELECTRICAL WIRING

5 STUDY OF ELECTRICAL MATERIALS AND WIRING COMPONENTS

6 VERIFICATION OF OHM’S LAW AND KIRCHHOFF’S LAWS

7 CALCULATION OF POWER US ING SINGLE PHAS E WATTMETER

8 CALCULATION OF ENERGY US ING S INGLE PHAS E ENERGYMETER

9 WIRING CIRCUIT FOR A LAMP US ING SINGLE AND S TAIR CAS E SWITCHES

10 FLUORES CENT LAMP WIRING

11

MEAS UREMENT OF RES ISTANCE TO EARTH OF AN ELECTRICAL EQUIPMENT

12

STUDY OF DIFFERENT TYPES OF LAMPS

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STUDY OF ELECTRONIC COMPONENTS - RESISTORS,

(COLOR CO DING) CAPACITO RS AN D INDU CT ORS

Aim:

To study electronic components and equipment such as resistor colour coding, Inductors,

Capacitors and usage of Multimeter.

Apparatus Required:

1. Resistors 2. Capacitors

3. Inductors 4. Multimeter

THEORY: An electronic circuit is made up of a large number of components and a necessary

interconnection between the components is made to produce the desire functionality.

Electronic components are broadly classified into mechanical, electro mechanical, passive

and active components. Passive and active components are very important to design

electronic circuits. ACTIVE components increase the power of a signal and must be supplied with the signal

and a source of power. Examples are bipolar transistors, field effect transistors etc. The

signal is fed into one connection of the active device and the amplified version taken from

another connection. In a transistor, the signal can be applied to the base connection and the

amplified version taken from the collector. The source of power is usually a dc voltage

from a battery or power supply. PASSIVE components do not increase the power of a signal. They often cause power to be

lost. Some can increase the voltage at the expense of current, so overall there is a loss of

power. Resistors, capacitors, inductors and diodes are examples of passive components.

RESISTOR COLOUR CODING TECHNIQUE: A typical resistor with color bands is shown in figure

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The above resistor has 4 color bands.

The first band represents first digit

The second band represent second digit

The third band represent multiplier (this gives the no. of zeros after the 2 digits ) The 4th band represents tolerance in %

If third band is gold the first two digit are multiplied by 10-1 If the third band is silver the first two digits are multiplied by 10-2

If the 4th band is gold the tolerance is ±5 %

If the 4th band is silver is the tolerance is ±10 %

First digit

for Second

digit for Multiplier

digit for Resistance

the 1st band

the 2n d

band

the 3rd band tolerance

Blac k 0 0 100 -

Brown 1 1 101 ±1%

Re d 2 2 102 ±2%

Ora nge 3 3 103 ±3%

Ye llow 4 4 104 -

Green 5 5 105 -

Blue 6 6 106 -

Viole t 7 7 107 -

Gra y 8 8 108 -

White 9 9 109 -

Gold - - 10-1 ±5%

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The colour codes are presented in the below Table

If the 4th band is no color the tolerance is ±20 %

If third band is gold the first two digit are multiplied by 10-1

If the third band is silver the first two digits are multiplied by 10-2

If the 4th band is gold the tolerance is ±5 %

If the 4th band is silver is the tolerance is ±10 %

If the 4th ba nd is no c olor the tole ra nce is ±20 %

The numerical value associated with each color

B B R O Y G B V G W

black brown red orange Yellow green blue violet gray White

0 1 2 3 4 5 6 7 8 9

EXAMPLES

The resistor has a color band sequence green, blue, brown and silver identify the

resistance value.

Silver - - 10-2 ±10%

No c olor - - - ±20%

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1ST Band 2nd band 3rd band 4th band

1st digit 2nd digit multiplier Tolerance

5 6 101 ±10%

The resistance value=56x101±10%

=560Ω±10%

Therefore the resistance should be within the range of 555Ω to 565Ω

Capacitors

Capacitors are capable of storing charges. They are used for coupling ac signals from

onecircuit to another and for frequency selection etc. A capacitor consists of 2 metallic

plates separated by a dielectric. The capacitance is defined as : C = Єo Єr A / d, where A

is the area of plates, d is plates separation, Єo is permittivity of free space and Єr is relative

permittivity. An important parameter for capacitors is its voltage handling capacity beyond

which the capacitor dielectric breaks down.

The value of a capacitor depends upon the dielectric constant (K = Єo Єr.) of the material.

There are three main classes of capacitors:

(i) Non electrolytic or normal capacitors and

(ii) electrolytic capacitors and

(iii) variable capacitors.

(iv) Normal capacitors are mostly of parallel plate type and can have mica, paper,

ceramic or polymer as dielectric. In the paper capacitors two rectangular metal foils

are interleaved between thin sheets of waxed paper and the whole system is rolled

to form a compact structure. Each metal foil is connected to an electrode. In mica

capacitors alternate layers of mica and metal are clamped tightly together.

In electrolytic capacitor mostly a then metal-oxide film is deposited by means of

electrolysis on axial electrode. That’s how it derives its name. During electrolysis the

electrode acts as anode whose cathode is a concentric can. Since the dielectric layer is very

thin hence these require special precaution for their use: i.e. they have to connected in the

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right polarity failing which the dielectric breaks down. Besides these fixed value capacitors

we also have variable capacitors whose value depends upon the area of crossection. They

have a fixed set of plates and a movable set of plates which can be moved through a shaft.

This movement changes the area of overlap of the two sets of plates which c hanges its

capacity. Refer fig .

Electrolytic Capacitors: There are two designs of electrolytic capacitors: (ii) Axial where

the leads are attached to each end (220µF in picture) and (iii) Radial where both leads are

at the same end (10µF in picture).

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(iii) Non-polarised capacitors ( < 1µF):Small value capacitors have their values printedbut

without a multiplier. For example 0.1 means 0.1µF = 100nF. Sometimes the unit is placed

in between 2 digits indicating a decimal point. For example: 4n7 means 4.7nF.

Inductors

Inductor is a component made by a coil of wire which is wound on a core. It is

used to vary the impedance of a circuit or for frequency tuning. The value of an inductor

depends upon the total number of turns (N), area of crossection of the core (A) and length

of the core (l).The formula is L = μo μr N2 A / l. Its unit is in Henry.

Results:

ENGINEERING PRACTICES LAB MANUAL

STUDY OF CRO (Cathode Ray Oscilloscope)

AIM:

To observe front panel control knobs of CRO and to find amplitude, time period,

frequency for given waveforms.

Apparatus Required:

Cathode Ray Oscilloscope, function generator, connecting wire.

Front Panel Controls

(1) Power ‘On/Off’ : Push buttons switch for supplying power to instrument.

(2) x10 : Switch when pushed gives 10 times magnification of the X signal.

(3) XY : Switch when pressed cuts off the time base & allows access to the external

horizontal signal to be fed through CH2 (used for X-Y display).

(4) CH 1/2 : Switch selects channel & trigger source (released Trig 1/2 CH1 & pressed

CH2).

(5) Mono/ Dual : Switch selects Mono or Dual trace operation.

(6) Alt/ Chop/ Add : Switch selects alternate or chopped in Dual mode. If Mono is selected

then this switch enables addition or subtraction of channel i.e.CH1 ± CH2.

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(7) Ext : Switch when pressed allows external triggering signal to be fed from the socket

marked Trigger Input (20).

(8) Line : Switch when pressed displayed signal synchronized with mains line frequency.

(9) Alt : Selects alternate trigger mode from CH1 & CH2. In this mode both the signals are

synchronized.

(10) Slope (+/-) : Switch selects the slope of triggering, whether positive going or negative

going.

(11) Auto/Level : Switch selects Auto/Level position. Auto is used to get trace when no

signal is fed at the input. In Level position the trigger level can be varied from the positive

peak to negative peak with Level Control.

(12) Level : Controls the trigger level from peak to peak amplitude of signal.

(13) Component : Switch when pressed starts CT operation.

(14) X Shift : Controls horizontal position of the trace.

(15) Hold ‘Off’ : Controls Hold Off time between sweeps. Used for Stable Triggering of

composite signals.

(16) TB Var : Controls the time speed in between two steps of Time/Div switch. For

calibration put this pot fully anticlockwise at Cal position. Lamp glows for uncalibrated

position.

(17) Trace Sep : Trace Separator x1 & x10 in 4 trace operation (Alt).

(18) Intensity : Controls the brightness of the trace.

(19) TR : Trace Rotation controls the alignment of the trace with graticule (screw driver

adjustment).

(20) Focus : Controls the sharpness of the trace.

(21) DC/AC/GND : Input coupling switch for each channel. In AC the signal is coupled

through 0.1MFD capacitor.

(22) CH 1 (Y) & : BNC connectors serve as input connection for CH 2 (X) : CH1 & CH2.

Channel 2 input connector also serves as horizontal external Input.

(23) Invert CH2 : Switch when pressed invert polarity of CH2.

(24) Component Tester Input : To test any components in the CT mode, put one test prod in

this socket and connect the other test prod in ground socket.

(25) Cal Out : Socket provided for square wave output 200mV used for probe

compensation and checking vertical sensitivity, etc.

(26) Digital Readout : LCD window for displaying Digital Readout for Volt/Div. &

Time/Div. settings.

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(27) Y Pos 1 & 2 : Controls provided for vertical deflection of trace for each channel.

(28) Volts/Div CH1 : Switch selects Volt/Div. step for CH1 & CH2

(29) Time /Div : Switch selects Time/Div. steps.

(30) Normal/Alternate : Switch selects Normal (x1) or Alternately expanded (x1 & x10)

simultaneous positions.

OBSERVATIONS:-

Measurement of Amplitude and frequency:

Amplitude = no. of vertical divisions * Volts/div.

Time period = no. of horizontal divisions * Time/div.

Frequency=1/T

Amplitude is taken on vertical section (y)

Time period taken on horizontal section(x)

Model Waveform

To find following using CRO:

1. Measurement of current

2. Measurement of voltage

3. Measurement of power

4. Measurement of frequency

Model Calculation:

RESULTS:

ENGINEERING PRACTICES LAB MANUAL

STUDY OF DIFFERENT TYPES OF LAMPS

AIM:

To study about the different types of lamps such as Fluorescent lamps, LED, CFL,

flood lights and Halogen Lamps and discuss about its applications.

Fluorescent lamp

Fluorescent lamp or a fluorescent tube is a low pressure mercury-vapor gas-

discharge lamp that uses fluorescence to produce visible light. An electric current in the gas

excites mercury vapor which produces short-wave ultraviolet light that then causes a

phosphor coating on the inside of the bulb to glow. A fluorescent lamp converts electrical

energy into useful light much more efficiently than incandescent lamps. The typical

luminous efficacy of fluorescent lighting systems is 50–100 lumens per watt, several times

the efficacy of incandescent bulbs with comparable light output.

Main parts of Fluorescent Tube Light:

1.Fluorescent Tube

2.Ballast

3.Starter

4.Holder, wire etc.

Construction

Fluorescent lamp tube is filled with a gas containing low pressure mercury vapor

and argon, xenon, neon, or krypton. The pressure inside the lamp is around 0.3% of

atmospheric pressure. The inner surface of the lamp is coated with a fluorescent (and often

slightly phosphorescent) coating made of varying blends of metallic and rare-earth

phosphor salts. The lamp's electrodes are typically made of coiled tungsten and usually

referred to as cathodes because of their prime function of emitting electrons. For this, they

are coated with a mixture of barium, strontium and calcium oxides chosen to have a low

thermionic emission temperature.

Fluorescent lamp tubes are typically straight and range in length from about 100

millimeters (3.9 in) for miniature lamps, to 2.43 meters (8.0 ft) for high-output lamps.

Some lamps have the tube bent into a circle, used for table lamps or other places where a

more compact light source is desired.

Fluorescent lamps are negative differential resistance devices, so as more current

flows through them, the electrical resistance of the fluorescent lamp drops, allowing for

even more current to flow. Connected directly to a constant-voltage power supply, a

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fluorescent lamp would rapidly self-destruct due to the uncontrolled current flow. To

prevent this, fluorescent lamps must use an auxiliary device, a ballast, to regulate the

current flow through the lamp.

The simplest ballast for alternating current (AC) use is an inductor placed in series,

consisting of a winding on a laminated magnetic core. The inductance of this winding

limits the flow of AC current. When operated with DC, the ballast must be resistive, and

would consume about as much power as the lamp.

Fluorescent Light Wiring Diagram

The starter is like a key of fluorescent light because it is used to light up the tube.

When we connect the AC supply voltage to the circuit, then the starter act like short

circuited and current flow through those filament (located at the first and second end of the

tube light) and the filament generate heat and it ionized the gas (mercury vapor) in the

fluorescent tube lamp. So the gas becomes electrically conductive medium. At the same

time when the starter opened the circuit path of two filaments from series connected, then

the ballast release its stored voltage. And it makes the fluorescent tube fully lighten. Now

the starter has no job in the circuit, if we open it from the circuit the fluorescent tube light

will be still lighten, until we release the main supply

These bulbs work by passing a current through a tube filled with argon gas and

mercury. This produces ultraviolet radiation that bombards the phosphoro us coating

causing it to emit light. Bulb life is very long - 10,000 to 20,000 hours.

Advantages

Luminous efficacy: fluorescent lamps convert more of the input power to visible

light than incandescent lamps

Life: Typically a fluorescent lamp will last 10 to 20 times as long as an equivalent

incandescent lamp when operated several hours at a time. Under standard test

conditions general lighting lamps have 9,000 hours or longer service life

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Lower luminance: compared with an incandescent lamp, a fluorescent tube is a

more diffuse and physically larger light source.

Lower heat: Fluorescent lamps give off about one-fifth the heat of equivalent

incandescent lamps. This greatly reduces the size, cost, and energy consumption

Disadvantages

If the lamp is installed where it is frequently switched on and off, it will age rapidly.

Under extreme conditions, its lifespan may be much shorter than a cheap

incandescent lamp

If a fluorescent lamp is broken, a very small amount of mercury can contaminate

the surrounding environment. About 99% of the mercury is typically contained in the

phosphor, especially on lamps that are near the end of their life

Fluorescent lamps emit a small amount of ultraviolet (UV) light.

Fluorescent lamps require a ballast to stabilize the current through the lamp, and to

provide the initial striking voltage required to start the arc discharge.

At much lower or higher temperatures, efficiency decreases.

LED (Light Emitting Diode)

A light emitting diode (LED) is known to be one of the best optoelectronic devices

out of the lot. The device is capable of emitting a fairly narrow bandwidth of visible or

invisible light when its internal diode junction attains a forward electric current or voltage.

The biggest advantage of this device is its high power to light conversion efficiency. The

response time of the LED is also known to be very fast in the range of 0.1 microseconds

when compared with 100 milliseconds for a tungsten lamp. Due to these advantages, the

device wide applications as visual indicators and as dancing light displays.

LED Circuit Symbol

Advantages of LED’s

Very low voltage and current are enough to drive the LED.

Voltage range – 1 to 2 volts.

Current – 5 to 20 milliamperes.

Total power output will be less than 150 milliwatts.

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The response time is very less – only about 10 nanoseconds.

The device does not need any heating and warm up time.

Miniature in size and hence light weight.

Have a rugged construction and hence can withstand shock and vibrations.

An LED has a life span of more than 20 years.

Disadvantages

A slight excess in voltage or current can damage the device.

The device is known to have a much wider bandwidth compared to the laser.

The temperature depends on the radiant output power and wavelength.

FLOOD LIGHT

Floodlights are broad-beamed, high- intensity artificial lights. They are often used to

illuminate outdoor playing fields while an outdoor sports event is being held during low-

light conditions. More focused kinds are often used as a stage lighting instrument in live

performances such as concerts and plays.

Types of floodlight

The most common type of floodlight is the Metal Halide which emits a bright white

light (typically 75-100 lumens/Watt). Sodium Vapor Lamps are also commonly used for

sporting events, as they have a very high lumen-to-watt ratio (typically 80–140

lumens/Watt), making them a cost-effective choice when certain lux levels must be

provided.

This white LED flood lights illuminates the porch with cool white light. The circuit

is too simple and energy saving design. Its current consumption is practically nil but can

provide light like a 20 watt CFL lamp. It is directly connected to AC lines to eliminate a

bulk transformer. Ultra white LEDs are now replacing the fluorescent lamps due to its

energy saving property and simplicity of design.

CFL bulbs

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A compact fluorescent lamp (CFL), also called compact fluorescent light, energy-

saving light, and compact fluorescent tube, is a fluorescent lamp designed to replace an

incandescent lamp; some types fit into light fixtures formerly used for incandescent lamps.

The lamps use a tube which is curved or folded to fit into the space of an incandescent

bulb, and a compact electronic ballast in the base of the lamp.

The principle of operation in a CFL bulb remains the same as in other fluorescent

lighting: electrons that are bound to mercury atoms are excited to states where they will

radiate ultraviolet light as they return to a lower energy level; this emitted ultraviolet light

is converted into visible light as it strikes the fluorescent coating on the bulb (as well as

into heat when absorbed by other materials such as glass).

CFLs radiate a spectral power distribution that is different from that of incandescent

lamps. Improved phosphor formulations have improved the perceived color of the light

emitted by CFLs, such that some sources rate the best "soft white" CFLs as subjectively

similar in color to standard incandescent lamps

There are two types of CFLs: integrated and non- integrated lamps. Integrated lamps

combine the tube and ballast in a single unit. These lamps allow consumers to replace

incandescent lamps easily with CFLs.

Integrated CFLs work well in many standard incandescent light fixtures, reducing

the cost of converting to fluorescent. 3-way lamp bulbs and dimmable models with

standard bases are available.

Non-integrated CFLs have the ballast permanently installed in the luminaire, and

only the lamp bulb is usually changed at its end of life.

CFLs have two main components: a magnetic or electronic ballast and a gas-filled

tube (also called bulb or burner).

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Electronic ballasts contain a small circuit board with rectifiers, a filter capacitor and

usually two switching transistors. The incoming AC current is first rectified to DC, then

converted to high frequency AC by the transistors, connected as a resonant series DC to

AC inverter. The resulting high frequency is applied to the lamp tube. Since the resonant

converter tends to stabilize lamp current (and light produced) over a range of input

voltages, standard CFLs do not respond well in dimming applications. Special electronic

ballasts (integrated or separate) are required for dimming service. CFL light output is

roughly proportional to phosphor surface area, and high output CFLs are often larger than

their incandescent equivalents. This means that the CFL may not fit well in existing light

fixtures. To fit enough phosphor coated area within the approximate overall dimensions of

an incandescent lamp, standard shapes of CFL tube are a helix with one or more turns,

multiple parallel tubes, circular arc, or a butterfly.

Tungsten lamps

These are the standard bulbs that most people are familiar with. Incandescent bulbs work

by using electricity to heat a tungsten filament in the bulb until it glows. The filament is

either in a vacuum or in a mixture of argon/nitrogen gas. Most of the energy consumed by

the bulb is given off as heat, causing its Lumens per Watt performance to be low. Because

of the filament's high temperature, the tungsten tends to evaporate and collect on the sides

of the bulb. The inherent imperfections in the filament causes it to become thinner

unevenly. When a bulb is turned on, the sudden surge of energy can cause the thin areas to

heat up much faster than the rest of the filament, which in turn causes the filament to break

and the bulb to burn out.

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Incandescent bulbs produce a steady warm, light that is good for most household

applications. A standard incandescent bulb can last for 700-1000 hours, and can be used

with a dimmer.

RESULTS:

ENGINEERING PRACTICES LAB MANUAL

SOLDERING OF SMALL ELECTRICAL AND ELECTRONIC CIRCUITS

Aim:

To practice soldering of small electrical and electronics circuits.

Apparatus Required:

1. Soldering iron

2. Solder

3. Flux

4. Resistor

5. Capacitor

6.LED

7.PCB (Printed Circuit Board)

8.Connecting Wires

Theory:

Soldering:

Soldering is the process of joining thin metal plates or wires made of steel, copper

or brass. It is very commonly used to join wires in electrical work and mount electronic

components on a circuit board. The joining material used in soldering is called as solder or

filler rod. An alloy of tin and lead is commonly used as the solder. The flux is used to clean

the surface of the plates/wires to be soldered. Aluminum chloride or zinc c hloride is

commonly used as flux. A good soldering iron is a variable temperature setting type with

interchangeable irons and tips. The tip should be removed regularly to prevent oxidation

scale from accumulating between the heating element and the tip.

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Fig.5: various Resistors, Symbols (R &C) and colour coding

Fig. Resistor Colour coding chart

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Circuit Diagram:

Procedure:

1. The surface to be soldered is cleaned and flux applied.

2. The soldering iron is heated to the required temperature.

3. The soldering iron melts the solder rod and a thin film of solder spreads over

the surface to join the plates/wires.

Soldering Simple Electronic Components:

A printed circuit board (PCB) consists of copper strips and pads bonded to a plastic

board. The copper strip is the network of interconnecting conductive path. Leads of

components mounted on the board are inserted through holes on the board and the

conductive copper. These leads are soldered to the copper at the end of the hole. If

excessive heat is applied to copper, it may get lifted from the board or the components on

the board get damaged. Soldering pencil gun of about 30 Watts is used to heat the junction.

The surface of copper bonded to the board should be properly prepared and cleaned before

soldering. Flux is applied on circuits and component leads. Check the conductive strips and

pads on the board before soldering. Avoid excess solder to prevent two copper paths from

bridging. When solder globules form on the junction area, remove them by cleaning the

soldering tip using a cloth.

Checking Continuity:

The continuity of a wire conductor without a break has practically zero ohms of

resistance. Therefore, an ohmmeter may be used to test continuity. To test continuity, select

the lowest ohm range. A wire may have an internal break, which is not visible due to

insulation, or the wire may have a bad connection at the terminals. Checking for zero ohms

between any two points tests the continuity. A break in the conducting path is evident from

the reading of infinite resistance.

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In a cable of wires, individual wires are identified with colours. Consider the figure,

where the individual wires are not seen, but you wish to find the wire that connects to

terminal A. This is done by, checking continuity of each wire to terminal A.

The wire that has zero ohms is the one connected to this terminal. Continuity of a

long cable may be tested by temporarily short-circuiting the other ends of the wires. The

continuity of both wires may be checked for zero ohms. In a digital multimeter, a beep

mode is available to check continuity. The connectivity between the terminals is identified

by the beep sound.

Results:

ENGINEERING PRACTICES LAB MANUAL

SAFETY ASPECTS OF ELECTRICAL WIRING

Aim:

To study the various aspects of electrical safety and study the various single phase

power protection equipments involved in electrical wiring and grounding.

Safety Precautions for Electrical Engineering Practice

Safety precautions are given below:

1. In case a person gets into contact with a live conductor, the mains is to be put

off immediately

2. Before attempting to disengage a person in contact with a live wire, one must insulate one self by standing on a dry rubber mat or wooden boards.

3. While working on a circuit, the corresponding fuse carrier should be taken away.

4. In the case of a fire, water should not be thrown on the live conductor.

5. The earthing has to be maintained well. 6. The switch is always to be connected on the live conductor.

7. In the case of an electric shock, after giving first aid, call a doctor. Continue first aid

till the doctor takes over. 8. Use wooden or PVC insulated handle screws drivers when working on electrical

circuits.

Preparation of Wiring Diagram

Wiring is the method of drawing or laying wires or cables and connecting accessories

and fitting for the purpose of distributing electrical power to the various points or

equipment from the mains.

1. Durability – Any wiring system must be able to withstand wear and tear due to weather. The atmospheric action should not affect the wiring system.

2. Safety – Safety is the most important point to be considered in the selection of any wiring system. The wiring should be perfectly leak proof.

3. Mechanical Protection – The wiring should be mechanically sound. It should be

properly protected from damages of physical nature 4. Appearance – The appearance of the wiring has an important bearing on the

architectural beauty of an edifice from the aesthetic point of view. 5. Environmental Conditions – In places where corrosive acids and alkalis are to

come in contact with wiring systems have to be protected against fumes and

dampness. 6. Accessibility – Facility for extension and renewal should be provided. The wiring

system adopted should be economical and should suit the individual.

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Earthing and Neutral

Ground or earth in a mains (AC power) electrical wiring system is a conductor

that exists primarily to provide a low impedance path to the earth to prevent the buildup of

voltages, static or transient (lightning), that may result in undue hazards to connected

equipment or persons, and which in normal operation does not carry current.

Neutral:

Neutral is a circuit conductor that may carry current in normal operation, and

which is usually connected to earth (bonding). The neutral point of a supply system is often

connected to earth ground, neutral and earths are closely related.

MCB (Miniature Circuit Breaker):

The MCB tripping is an indication either that the circuit has been overloaded or that

a short circuit has occurred somewhere in the system. Before resetting the MCB it is

important to identify what has caused it to trip. Switch off all the appliances connected to

the circuit to ensure it is not overloading. The following figure 2 shows the two pole

miniature circuit breaker.

FUSES

Introduction

If there is a fault in a piece of equipment then excessive current may flow. This will

cause overheating and possibly a fire. Fuses protect against this happening. Current from

the supply to the equipment flows through the fuse.

Fig.: Fuses

Definition

Fuse is an over current protective device containing a calibrated current carrying

member which melts and opens a circuit under specified over current conditions.

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Fuse ratings

Appliances up to 700 Watts = 3 Amp fuse

Appliances between 700 and 1000 Watts = 5 Amp fuse Appliances over 1000 Watts = 13 Amp fuse

Types of fuses

There are three basic types of fuses:

(1) Slow Blow/Time Lag/ Time Delay fuses

(2) Fast acting fuses

(3) Very fast acting fuses

A major type of Time Delay fuse is the dual-element fuse. This fuse consists of a

short circuit strip, soldered joint and spring connection. During overload conditions, the

soldered joint gets hot enough to melt and the spring shears the junction loose. Under short

circuit conditions, the short circuit element operates to open the circuit. Slow-blow fuse

allows temporary and harmless inrush currents to pass without opening, but is so designed

to open on sustained overloads and short circuits. Slow-blow fuses are ideal for circuits

with a transient surge or power-on inrush.

These circuits include: motors, transformers, incandescent lamps and capacitate

loads. This inrush may be many times the circuit's full load amperes. Slow-blow fuses

allow close rating of the fuse without nuisance opening. Typically, Slow Blow fuses are

rated between 125% to 150% of the circuit's full load amperes.

Results:

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STUDY OF ELECTRICAL MATERIALS AND WIRING COMPONENTS

Aim:

To study the different types of lamp holders, sockets, reflectors, holders etc for

domestic & commercial single phase power supply.

LAMP HOLDER

Use: Lamp holder is used to hold the lamp.

Material used: Earlier brass holder is commonly used. Nowadays they are replaced by

Bakelite- insulated holders.

Lamp holders used in practice:

(1) Bayonet cap lamp holder:

The bulb is fitted into the slots provided in the skirt and is held in position by means

of two pins in lamp cap. These lamp holders have two solid or hollow spring contact

terminals. The supply mains through the switches are connected to these contacts. Bayonet

lamp holder is used for lamp of wattages below 200W.

Types of Bayonet lamp holders:

Batter Holder Pendent Holder

Angle Holder

ENGINEERING PRACTICES LAB MANUAL

Bracket Holder

(2) Edison screw type lamp holder:

In this lamp holder, cap is provided with screw threads and the lamp used also has a

screw type cap. It has center contact which is connected to the live wire and the screwed

cap is connected to the neutral wire. These holders are used with those lamps whose

wattage in the range 200W – 300W.

(3) Wall Bracket:

There are many types of wall brackets in use and the use of particular one is

depends upon the nature of light required.

Angle type Wall Bracket:

If a light point is installed at an angle, then it is called angle type wall bracket.

L-type Wall Bracket:

If light outlets are to be installed projecting from the wall at angles of 90º,then it is

called L-type Wall Bracket.

ENGINEERING PRACTICES LAB MANUAL

Fancy Wall Bracket:

It is used for interior decorations.

(4)Ceiling Rose:

Ceiling roses are used as tapping points from the wiring for supplying power to

fans, pendant holders, tube lights, etc., by means of flexible wires. Their use is restricted to

those circuits whose voltage exceeds 250V.These are also made of Bakelite. Ceiling fans

should be installed at a height not less than 2.75m from the ground level.

Types of ceiling roses:

Two-plate ceiling point: Used for single light point.

Three-plate ceiling point: Used for bunch of lights.

Two-Plate Ceiling Point Three-Plate Ceiling Point

USES OF CEILING ROSE

Porcelain connectors:

These are made of porcelain clay and are of single, two and three ways. These serve

as tapping points from electrical installations for supplying power to the circuit and are

available in different current carrying capacities: 15, 30, 60 and 100 amps.

(5)Adapter lamp holder:

ENGINEERING PRACTICES LAB MANUAL

It is used for taking supply for portable appliances from the lamp holder. Its use is

not recommended. It should never be used in damp places such as bathrooms, etc.

Iron connectors or Press connectors:

These are used as female connectors to supply current to electric kettles, presses,

heaters, etc. These connectors are provided with two pin sockets and an earth connection

strip. They are available in flat or round shape with top or side entry for cable.

Reflectors and Shades:

The main idea of using these shades or reflectors is to give even illumination and

prevent direct glare from the filament. Different types of reflectors available to suit

different types of lamps and illumination required. They are: Tube reflector, Lamp shade

and Fancy lamp shade.

(6)Lamp

holder of fluorescent tube:

The fluorescent tube lamp holders are of two types:

(i) Two-Pin: Pin-type holders are generally used with 20watts tube. (ii) Bayonet Cap Type: For 40 watts tube bayonet cap type holder is used as cap.

ENGINEERING PRACTICES LAB MANUAL

ELECTRICAL SOCKETS

Electrical sockets are essential elements of electrical connectors. An electrical

socket constitutes the interface that enables transfer to a generic load of the level of AC

voltage of the electrical network to which the socket is connected. Socket contacts are

designed to insure low and stable electrical resistance through the connector, as well as

mechanical integrity for the connection. Electrical sockets of the two-conductor type

normally found in conventional electrical wall receptacles and electrical extension cords

generally include an insulated housing and a pair of transversely spaced, longitudinally

elongate, electrically conductive, contact bars or strips therein. In three-conductor type

sockets a grounded contact member is provided in addition to the transversely spaced

contact bars.

Safety notes

Connecting a plug or socket may seem simple, but if done improperly, can result in

a working but highly dangerous installation. Connecting live wire to the ground contact is very dangerous because the conductive case is made live and the appliance may cause death at any time.

Electricity around the world

There is no standard mains voltage throughout the world and also the frequency, i.e. the number of times the current changes direction per second, is not everywhere the same. Moreover, plug shapes, plug holes, plug sizes and sockets are also different in many

countries.

Single-phase voltage and frequency

Europe and most other countries in the world use a voltage which is twice that of the US. It is between 220 and 240 volts, whereas in Japan and in most of the Americas the

voltage is between 100 and 127 volts.

Plugs and sockets When electricity was first introduced into the domestic environment it was primarily

for lighting. As the need for safer installations grew, three-pin outlets were developed. The third pin on the outlet was an earth pin, which was effectively connected to earth, this being at the same potential as the neutral supply line. The idea behind it was that in the event of a

short circuit to earth, a fuse would blow, thus disconnecting the supply.

Below is a brief outline of the plugs and sockets used around the world in domestic environment. The outline map below visualizes the spread of the different plug types used

around the world.

ENGINEERING PRACTICES LAB MANUAL

Results:

ENGINEERING PRACTICES LAB MANUAL

Verification of Ohm’s Law and Kirchhoff’s Laws

Aim:

To expose to bread board connections and able to handle voltmeter and ammeters to

measure voltage and current respectively.

EQUIPMENTS/COMPONENTS REQUIRED:

Theory:

Ohms Law- Statement:

The current flowing through the electric circuit is directly proportional to the

potential difference across the circuit and inversely proportional to the resistance of the

circuit provided the temperature remains constant.

Kirchoff’s Current Law- Statement:

Kirchhoff’s current law states that the algebraic sum of all the current meeting at a

junction point is always equal to zero.

Kirchoff’s Voltage Law-Statement:

Kirchhoff’s voltage law states that in any network, the algebraic sum of the voltage

drops across the circuit elements of any closed path (loop or mesh) is equal to the algebraic

sum of the emf’s in the path.

Procedure:

S.

No

Name of the Equipment/

Component

Type Range Quantity

Require

d 1 Resistor - 1K 3

2 Ammeter

M

(0-30) mA

(0-30) mA

3

3 Regulated Power Supply (RPS)

DC

(0-30)V 1

4 Voltmeter MC (0-30)V 3

5 Bread board - - 1

6 Connecting wires - - As

Required

V=IR

I α V I α 1/R

ENGINEERING PRACTICES LAB MANUAL

Ohms Law:

1. Connect the circuit diagram as shown in the fig1 .

2. Set the RPS voltage V to measure the corresponding values of current I.

3. Calculate the theoretical current value by using ohms law.

4. Repeat the above procedure for different values of voltage.

Kirchhoff’s Current Law:

1. Connect the circuit as shown in Fig .

2. Switch ON the Regulated Power Supply (RPS) and set the RPS to a particular value of

voltage say 5V.

3. Record the readings of three ammeters namely I1, I2, I3 with proper sign by taking

current entering the node as positive and leaving the node as negative in the observation

Table (1).

4. Add I2 and I3 and verify whether the added value is equal to I1. (As per Kirchhoff’s law

I1=I2+I3).

5. Increase the RPS settings in steps of 5V up to a maximum of 25V.

Kirchhoff’s voltage law:

1. Connect the circuit as shown in Fig .

2. Switch ON the Regulated Power Supply (RPS) and set the RPS to a particular value of

voltage say 5V.

3. Record the readings of two voltmeters V1, V2 and RPS voltage in the observation Table

(2).

4. Add V1 and V2 and verify whether the added value is equal to V. (As Per Kirchhoff’s

Voltage law V=V1+V2).

5. Increase the RPS settings in steps of 5V up to a maximum of 25V.

6. Repeat the steps 3 to 5 for each value of RPS setting.

Circuit Diagram: Ohms Law

ENGINEERING PRACTICES LAB MANUAL

Tabulation: Ohms law

SNo. Input Voltage

(V)

Resistance R

(KΩ)

Practical Output

Current I (mA)

Theoretical Current

I=V/R (mA)

1

2

3

Circuit Diagram : KCL & KVL

ENGINEERING PRACTICES LAB MANUAL

Tabulation: Kirchhoff’s current law:

S.No RPS

Voltage (V) I1 (mA) I2 (mA) I3 (mA) I1= I2+I3(mA)

Theoretical

Current

1.

2.

3.

4.

5.

Tabulation: Kirchhoff’s voltage law:

S.No RPS

Voltage (V)

V1

(Volts)

V2

(Volts)

V3

(Volts)

V=V1+V2+ V3

(Volts)

Theoretical

Voltage

1.

2.

3.

4.

5.

ENGINEERING PRACTICES LAB MANUAL

Model calculations:

Ohms law:

Kirchhoff’s current law:

Kirchhoff’s voltage law:

Results:

ENGINEERING PRACTICES LAB MANUAL

CALCULATION OF POWER USING SINGLE PHASE WATTMETER

Aim:

To calculate the power consumed by the load using single phase wattmeter.

Apparatus Required:

S.No Name of the apparatus Type Range Quantity

1 Ammeter MI (0-5/10A) 1

2 Voltmeter MI (0-300V) 1

3 Resistive load - - 1

4 Single phase wattmeter - - 1

5 Connecting wires - - As per required

Theory

Single phase induction type energy meter is also popularly known as watt-hour

meter. This name is given to it. This article is only focused about its constructional features and its working. Induction type energy meter essentially consists of following components:

1. Driving system 2. Moving system

3. Braking system and 4. Registering system

The basic working of Single phase induction type Energy Meter is only focused on two

mechanisms:

1. Mechanism of rotation of an aluminum disc which is made to rotate at a speed

proportional to the power. 2. Mechanism of counting and displaying the amount of energy transferred.

The metallic disc is acted upon by two coils. One coil is connected or arranged in such

a way that it produces a magnetic flux in proportion to the voltage and the other produces a

magnetic flux in proportion to the current. The field of the voltage coil is delayed by 90

degrees using a lag coil. The aluminum disc is supported by a spindle which has a worm

gear which drives the register. The register is a series of dials which record the amount of

energy used.

ENGINEERING PRACTICES LAB MANUAL

Formula used:

Indicated power = Observed power X Multiplying factor

Actual Power = V I CosӨ (Since CosӨ=1)

Error = (Actual Power – Indicated Power)/(Actual Power) X 100

Circuit Diagram

Fig: Circuit diagram for measurement of Power using single phase wattmeter

Procedure:

Before switching ON the supply to the circuit,

1. Multiplication factor for all the meters must be noted.

2. All the loads must be kept in OFF position. 3. All the connections are made as per the circuit diagram. 4. The availability of the supply should be checked using line tester.

After switching ON the supply to the circuit,

1. The load is gradually increased. 2. For each load condition, the corresponding ammeter reading, voltmeter reading and

watt meter reading are noted. 3. The load should not be increased more than the rated current i.e. we can adjust the

load up to 8A (for resistive load) or 4A (for rheostat load).

4. Then the power consumed by the load is calculated for various load current by using the formula.

ENGINEERING PRACTICES LAB MANUAL

Model Graph

Fig: Model graph for current vs %error

Tabulation

S.No. Ammeter

reading(A)

Voltage

reading (V)

Wattmeter reading(W) Actual

Power

Error(%)

Observed

value

Indicated

Power

Results:

ENGINEERING PRACTICES LAB MANUAL

CALCULATION OF ENERGY USING SINGLE PHASE ENERGYMETER

Aim:

To calculate the energy consumed by the load using single phase energy meter.

Apparatus Required:

S.NO NAME OF THE APPARATUS TYPE RANGE QUANTITY

1 Ammeter MI (0-5/10A) 1

2 Voltmeter MI (0-300V) 1

3 Resistive load - - 1

4 Single phase Energy meter - - 1

5 Single phase Wattmeter - - 1

6 Stop watch - - 1

7 Connecting wires - - As per required

Theory

Induction type energy meters are most commonly form of an AC. KWh meter used to

measure the energy consumed in any AC circuit in a prescribed period when supply voltage

and frequency are constant. Energy meter is an integrating instrument which measure the

total quantity of electrical energy supplied to the circuit in a given period. These meters

measure electrical energy in Kilowatt hours.

The Basic principle of induction type energy meter is electromagnetic induction. When an

alternating current flows through two suitably located coils (Current coil & Potential Coil)

produces rotating magnetic field which is cut by the metallic disc Suspended near to the

coils, thus, an E.M.F. is induced in the thin Aluminum disc which circulates eddy currents

in it. By the interaction of rotating magnetic field and eddy currents, torque is developed

and causes the disc to rotate. Construction: An Indction type single phase energy meter, has

following main parts of the operating mechanism:

ENGINEERING PRACTICES LAB MANUAL

Driving System

Moving System

Braking System

Registering System

Formula used:

Energy meter specification, 1200 rev/Kwhr = 1 Kwhr

1rev = 1Kwhr/1200 = (3600 * 100) / 1200 = 3000 Watt – sec

For UPF conditions, Power calculated from energy meter reading = 3000 / (time taken for

10rev)

%Error =(Power calculated from energy meter reading – wattmeter reading) /(Wattmeter

reading) * 100

Circuit Diagram

Fig: Circuit diagram for measurement of energy using single phase Energymeter

Procedure:

Before switching ON the supply to the circuit,

Multiplication factor for all the meters must be noted.

Energy meter constant of the energy meter must be noted.

ENGINEERING PRACTICES LAB MANUAL

All the loads must be kept in OFF position (If the rheostats are used as load, it must be kept

at maximum resistance position).

All the connections are made as per the circuit diagram.

The availability of the supply should be checked using line tester.

After switching ON the supply to the circuit,

The load is gradually increased.

For each load condition, the corresponding ammeter reading, voltmeter reading and time

taken for ten revolutions or ten flickering in energy meter are noted.

The load should not be increased more than the rated current i.e. we can adjust the load up

to 8A (for resistive load) or 4A (for rheostat load).

Then the energy consumed by the load is calculated for various load current by using the

formula.

Model Graph

Fig: Model graph for current vs %error

ENGINEERING PRACTICES LAB MANUAL

Tabulation

S.

No

.

Voltmeter

reading (V)

Ammeter

reading(A)

Time for 5

revolutions

(Sec)

Wattmeter reading(W) Power

from

Energy

meter(W)

Error(%)

Observed

value

Actual

value

Results:

ENGINEERING PRACTICES LAB MANUAL

WIRING CIRCUIT FOR A LAMP USING SINGLE AND STAIR CASE

SWITCHES

Aim:

To design and test the wiring circuit for a lamp using single and stair case switches.

Apparatus Required:

S.no Name of the apparatus Type Range Quantity

1 Two way switch - 230V/5A 2

2 One way switch - 230V/5A 1

3 Incandescent lamp - 230V,40W 1

4 PVC pipes - - -

5 Screw driver - - -

6 Cutting pliers - - 1

7 Drilling machines - - 1

8 Round blocks, junction box - - 1

9 Screws, T joints and clamps - - -

10 Lamp holder, connecting wires - - -

Circuit Diagram

Single way switch operation:

The single way switch is operated as mentioned in the table 2 and the corresponding

condition of the lamp is verified.

ENGINEERING PRACTICES LAB MANUAL

The condition of the lamp for single way switch is checked against each and every switch

positions as shown in the table 1.

Table:1

S.No Switch position Condition of the Lamp

1 On On

2 Off Off

Staircase wiring using two way switches:

The stair case wiring using two way switch for both the operations 1 and 2 are

given as shown in Fig. 2 and Fig. 3 respectively and the corresponding condition of the

lamp are verified from the table 2 and 3.

Operation 1:

Fig: Staircase wiring using two way switches

Then the condition of the lamp for stair case switch is checked for different positions of its

switch as shown in the table 2.

Table: 2

S.No Switch position Condition of the Lamp

S1 S2

1 On On On

2 On Off Off

3 Off On Off

4 Off Off On

ENGINEERING PRACTICES LAB MANUAL

Operation 2:

Fig. 4: Staircase wiring using two way switches cross connection

Table: 3

S.No Switch position Condition of the Lamp

S1 S2

1 On On Off

2 On Off On

3 Off On On

4 Off Off Off

Procedure:

Before switching ON the supply to the circuit,

1. The pipe layout of the respective wiring is laid on the board. 2. The PVC pipes are fixed to the wooden board. 3. The junction box and switch box are fixed at appropriate positions.

4. The round blocks are tightened in their position with the help of a screw driver. 5. The wires are inserted into the pipes and the connections for different types of

switch connections are made as per the circuit diagram. 6. Switch ON the supply to the circuit and verify the operations using table.

ENGINEERING PRACTICES LAB MANUAL

After switching ON the supply to the circuit,

1. The lamp is checked for its glow.

2. After making all the changes in the circuit, the sequential process for the lamp glow is checked.

Results:

ENGINEERING PRACTICES LAB MANUAL

FLUORESCENT LAMP WIRING Aim: To connect the components as per the circuit diagram of fluorescent t lamp wiring and learning various aspects of Fluorescent Lamp wiring.

APPARATUS REQUIRED:

S.No Name of the Range Quantity

1 Fluorescent Lamp Holder 4 ft

1 No

2 Fluorescent Lamp 40W 1 No

3 Choke 40W, 230V 1 No

4 Starter 1 No

5 Wires 1/18 guage

As per

requirement

CIRCUIT DIAGRAM:

ENGINEERING PRACTICES LAB MANUAL

TESTING OF CHOKE :

TESTING OF STARTER : TESTING OF FLUORESCENT LAMP :

WORKING OF THE FLUORESCENT TUBE LIGHT :

The fluorescent lamp circuit consists of a choke, starter, a fluorescent tube and a

frame. The length of the commonly used fluorescent tube is 100cm and its power rating is

40W and 230V. The tube is filled with argon and a drop of mercury. When the supply is

switched on, the current heats the filaments and initiates emission of electrons. After one or

two seconds, the starter circuit opens and makes the choke to induce a momentary high

voltage surge across the two filaments. Ionization takes place through argon and produces

bright light.

ENGINEERING PRACTICES LAB MANUAL

THEORY:

Tube light has filament on either side. They are coated with tungsten material. The

inside of the tube has phosphorous coating which is used to convert ultraviolet into visible

light and to give the required color sensation. A choke is used to give transient high voltage

so as to initiate the electron movement which is an iron starter capacitor is used to suppress

radio- interference with the switch closed. The current flows through the choke and the

starter. The glow switch suddenly breaks thereby creating the c ircuit. Due to high

conductivity, inductive property of the choke, a transient high voltage is available across

the filament. Hence the electrons are emitted and travel through the tube. Then tube light is

produced.

PRECAUTIONS:

1. While giving the connection be careful.

2. Handle the lamp safely.

3. Be careful while handling the tools.

4. All the connections should be right and tight.

Procedure

1. Mark the switch and tube light location points and draw lines for wiring on the

wooden board.

2. Place wires along the lines and fix them with the help of clips.

3. Fix the switch and tube light fitting in the marked positions.

4. Complete the wiring as per the wiring diagram.

5. Test the working of the tube light by giving electric supply to the circuit.

Results

ENGINEERING PRACTICES LAB MANUAL

MEASUREMENT OF RESISTANCE TO EARTH OF

AN ELECTRICAL EQUIPMENT

AIM:

To measure the earth resistance using Megger.

APPARATUS REQUIRED:

1.Megger

2.Electrodes

3.Hammer

4.Connecting Wires

5.Tester

THEORY:

Earthing means generally connected to the mass of the earth. It shall be in such a means as

to ensure at all times an immediate & safe discharge of electric current due to leakage, fault

etc. All metallic parts of every electrical insulation such as conduit, metallic sheathing,

metallic panels, motor, gear, Transformer regulator shall be earthed using continuous bus

wire if one earth bus for installation is found impracticable move than one earthing system

shall be introduced the earthing conductors when taken outdoors to the earthing point, shall

be incased in pipe securely supported and continued upto point not less than 0.3m below

the ground. No joints are permitted in earth bus whenever there is lighting conductors

system installed in a building. Its earthing shall not be bonded to the earthing of electric

installation. Before the electric supply on apparatus is energized all earthing system shall

be tested for electrical resistance to ensure efficient earthing. It shall not be more than

2ohms including the ohmic value of earth electrode.

ENGINEERING PRACTICES LAB MANUAL

CIRCUIT DIAGRAM:

1. CURRENT ELECTRODE 2. POTENTIAL ELECTRODE 3. EARTH

BLOCK DIAGRAM:

ENGINEERING PRACTICES LAB MANUAL PROCEDURE:

1. Collect the materials required for this experiment. 2. The terminal of ohmmeter E is first connected to earth. 3. The two earth rods are fixed to feet away from the ohmmeter. So that they are triangle

with base 50 feet. 4. The wires are connected to each rod and the ohmmeter terminals are shown. 5. The ohmmeter is ranked and the readings are taken.

RESULTS: