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# basicofelectrical-150117065543-conversion-gate02

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TO
BASIC ELECTRICITY
TRAINING
OBJECTIVES
To be able to identify and implement. Theory of Ohms Law.
Define electrical terms.
To be able to describe the interrelationship between voltage,
current and resistance in electrical circuits.
To be able to identify digital multimeter features and its
capabilities.
To be able to correctly use the digital multimeter and understand
your findings when taking electrical measurements,in normal and
fault finding situations
Basics of electricity
Types of energy- Electrical energy
- Heat energy
- Atomic energy
- Mechanical energy
- One form of energy can be converted into another
OIL - Heat , Water - Steam , Turbine - Mechanical energy
Generator - Electrical energy
What is Electricity
PROTONS WITHIN NUCLEUS
Matter
ALL FORMS OF MATTER ARE
MADE UP OF MOLECULES
Molecule
IN TURN THESE
MOLECULES ARE MADE UP
OF ATOMS
NEUTRONS WITHIN NUCLEUS
ELECTRONS IN ORBIT
Atom
The centre of the atom is called the Nucleus
and contains Neutrons and protons.
ATOMS ARE MADE UP
OF PROTONS
,NEUTRONS AND
ELECTRONS.
ELECTRONS MAINTAIN A
NEGATIVE POLARITY- ve
PROTONS MAINTAIN A
POSITIVE POLARITY +ve
NEUTRONS DO NOT
HAVE ANY POLARITY
(are neutral)
What is Electricity
Three factor determine whether or not the Atom is a good or bad
CONDUCTOR
(1) The number of electrons in the outer orbit.
2)
The distance of the outer orbit from the Nucleus of the Atom.
(3) The density of the atoms within the element.
Rules
If the Atom has only one orbit,maximum number of electrons on orbit is two.
If Atom has more than one orbit maximum number of electrons on outer orbit is eight.
Gold, Silver and Copper have only one electron on their outer orbit Mercury has two,
Aluminium has three and remember Carbon has four.
ELECTRONS IN ORBIT
NUCLEUS
What is Electricity
COPPER ATOM ( good Conductor)
29 protons 29 electrons.
But only one loose electron On The outer orbit
CARBON ATOM. 4 ELECTRONS ON THE OUTER ORBIT
(semi conductor)
ELECTRONS IN ORBIT
NUCLEUS
PROTONS IN NUCLEUS
What is Electricity
An excess of electrons creates a negative charge.
The absence of electrons creates a positive charge
OPPOSITE CHARGES WILL ATTRACT EACH OTHER
LIKE CHARGES REPEL EACH OTHER
Normally an enormous number of Electrons flow.The basic unit of electric charge is the coulomb.
ONE COLOUMB EQUALS 6.25 X 1018 ELECTRONS,or 6,250,000,000,000,000,0000
ELECTRONS IN ORBIT
PROTONS IN NUCLEUS
What is Electricity
Electron flow
Conventional flow
load
+
Anode\positive
battery post
-
battery
switch
Cathode\negative
Electron flow
Conventional flow
load
+
Anode\positive
battery post
-
switch
battery
The loss of an electron by an atom makes it a positive ion, therefore it will attract an electron from a
neighbouring atom,to again become balanced.
Basics of electricity
Electricity- There are variety of methods for producing electricity
- Through chemical reaction in a battery.
- For large amount of electricity
electromagnetic generators are used.
Basics of electricityCurrent - Flow of electron.
- Conventional current is in opposite direction.
- High voltage to low voltage.
- Unit of current is ampere.
- Current is measured by ammeter, Connected
in series.
- Polarity in DC
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Basics of electricityPotential - Ability to do work
Voltage - Potential difference.(work done in moving a unit +ve charge
from a point of lower to higher potential).
- Unit of voltage is volt (v).
- Measured by voltmeter,connected across source.
- Sources can be Battery,DC generator,alternator etc.
- Can be AC or DC.
- Polarity in DC
- Equivalent to two water tanks,connected by pipe water
flows.
FUNDAMENTALS OF ELECTRICITY
VOLTAGE
CURRENT
VOLTAGE = ELECTRICAL PRESSURE
VOLTAGE
Voltage provides the electrical pressure or force that enables the current or electrons to flow.
Voltage is the difference in electrical pressure between two points in a circuit .
Voltage is measured in units called volts . The symbol for Voltage is E and the symbol for volt is
Basics of electricity
Resistance - Opposes flow of current.
- Unit is ohms.
- Measured by ohm meter connected across it.
- Depends upon type of material, area & length.
- Produces heat when current flows through it.
- Fixed and variable resistor (potentiometer).
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FUNDAMENTALS OF ELECTRICITY
RESISTANCE
RESISTANCE (OHMS).
Resistance is a restriction to current flow.
Increasing resistance will reduce flow of current.
Electrical resistance is measured in units called ohms, they are
abbreviated by the letter R, and the symbol is
Amps
electrons
 ( omega).
Basics of electricity
Inductor -
- Coil of wire.
- Opposes change in current.
- Used to create magnetic field for rotation.
- Unit is henry.
- Open and short inductor.
Basics of electricity
Capacitor -
- Two metal plates separated by a DI-electric (Max volts/mm which a
medium can withstand without breakdown).
- Gets charged when voltage is applied.
- Unit of capacitance is farad.
- Capacitor in series 1/C=1/C1+1/C2 & in parallel C= C1+C2.
-C=Q/V
- Practical unitsMicro and Pico farad.
Basics of electricity
Insulators and Conductors Conductors - Materials that have a low resistance to current flow
are classified as conductors.
- Copper and aluminium wires are conductors.
- Conductors are used in electrical circuits to connect
components to one another.
- Conductors are wrapped in insulators to isolate from
one another.
Insulators - Materials that have a high resistance to current flow
are classified as Insulators.
- Glass, rubber & dry air are insulators
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Basics of electricity
Ohm’s law - Relation between three quantities learnt
V= I x R
I = V/ R
R =V /I
Where R = Resistance of circuit, in ohms.
V = Applied voltage, in volts.
I = Current, in amperes.
OHMS LAW
Ohms Law Pie Chart
Resistance = Voltage over Current
E
I
E
R
Current = Voltage over Resistance
I
voltage = Current times Resistance
E
E
I
R
R
I
R
Basics of electricityDC power - Power consumed in industry is almost A.C.
- Power in DC circuit is P = V x I =I x R x I
- Different types of load have different effect
on power source.
- Unit of mechanical power is horsepower.
- 1 hp = 0.746 kilowatts.
- Measured by wattmeter.
DC POWER
P
APPLICATION OF THE POWER FORMULA.
V I
To find the power consumed by the resistor , the total current
(I t) has to be found first.
It = Va\R1
It = 10 volts \ 10 ohms
+
It = 1 AMP.
Va=10V
The power used by the resistor can then be found by :
P = It x Vt
P = 1 amp x 10 volts
P = 10 Watts

R1
DC POWER
The unit of power in mechanical system is the
P
HORSE POWER (hp).
One horsepower is equal to 0.746 kilowatts (KW).
TO CONVERT HORSE-POWER TO KILOWATTS.
multiply horsepower times 0.746 KW.
EXAMPLE.
P = Horsepower x 0.746 Kw
P = 50 Horsepower x 0.746 Kw
P = 37.3 Kw
Therefore a 50 Hp motor will consume 37.3 Kw of power
Basics of electricity
AC Power- Alternating quantity is one which periodically passes
through a definite cycle of changes.
- In AC RMS values are used .
- AC power is consumed by different types of load such
as inductive , resistive & capacitive.
- AC power is given by P= V x I x CosO
- Symbol for AC source.
- AC power is measured by Wattmeter.
- Unit of power is Watts.
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ELECTRICAL TERM
THE FOLLOWING TABLE SHOW SOME COMMON ELECTRICAL TERMS
THEIR ABRIVIATION, UNITS OF MEASURE, SYMBOL
AND MEASURING INSTRUMENTS.
Term
Abbreviation
Unit
Symbol
Measuring Tool
Current
I
Ampere
A
Ammeter
Voltage
E
Volt
V
Voltmeter
Resistance
R
Ohm
Power
P
Watt
Ohmmeter
W
Wattmeter
Basics of electricity
Series circuit - One path for current flow.
- Can have more than one load (e.g. resistance).
- Total load is sum of individual loads.
- Some voltage loss takes place across each
load and is called as voltage drop.
- Sum of voltage drops across each load is
equal to applied voltage.
- Current through each load is same.
- Open and short.
- Example - Chain of small bulbs.
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OPEN AND SHORT CIRCUIT
SHORT CIRCUITS occur when current does not go through its
intended path.This usually happens in circuits that have
improper wiring or defective electrical components.
In the diagram we have a series circuit in which R2&R3 are“shorted
out” to the source voltage.
R2 and R3look like a wire and the total resistance of the circuit
limited to R1.
More current will flow because the total resistance is less.
R1
R2
R3
current flows through the short.
no current flows through R2 or R3
current takes path of least
resistance.
OPEN AND SHORT CIRCUITS
If a short occurs in a parallel circuit , most of the source current
will flow through the short because the current takes the path
of
least resistance
+
R3
R2
R1
Most current will flows through short .
no current will flow through R2 or R3
FUNDAMENTALS OF ELECTRICITY
AMPERES SEVERE BURNS
6 AMPS TO
SOLENOID
1.0
DEATH
0.2
200 mA
DIFFICULT
BREATHING
OUCH !
0.01
100 mA
0.001
1 mA
IT TINGLES
CAN JUST FEEL IT
DIGITAL MULTIMETER DESCRIPTION.
Measures Electrical Characteristics.
Measures Multiple Types Of Electrical Characteristics with a
single device.
Functions as a Ohmmeter,Ammeter and Voltmeter.
Includes an AC, as well as DC Voltage range.
Provides a Display “ Screen “.
Includes option for an analog format.
The accuracy of the fluke meter is specified as
of the reading + ( number of least significant digits.)
EG. Voltage dc
DIGITAL MULTIMETER DESCRIPTION
ROTARY SWITCH.
To turn the meter on , turn the rotary switch from the OFF position .
The meter performs a selftest , then starts taking readings.
DIGITAL MULTIMETER DESCRIPTION
VOLTAGE MEASUREMENT
Measure in parallel across
item to be measured
Ranges
0 to1000 Volts dc
0 to 750 Volts ac
DIGITAL MULTIMETER DESCRIPTION
RESISTANCE MEASUREMENT
Measure in parallel across
item to be measured
Ranges
320.0 ohms
thro
32.00 Mohms.
CURRENT MEASUREMENT
Measure in series with
item to be measured
Ranges
AC. 320 mAmps &
10 Amps
DC. 320 mAmps &
10 Amps.
DIGITAL MULTIMETER DESCRIPTION
DIODE TEST
Measure in parallel across
item to be measured
Range
2 Volts dc.
Continuity test.
Bleep while
resistance is below
150 ohms
The Electrical Circuit
An electrical circuit can be compared to a simple hydraulic circuit.
Voltage drop (volts)
Battery
Ammeter
Motor
Amperes
S urce of pressure
o
Flow rate
Resistance to flow
Pressure drop (bar)
Liters / Min
Pump
Flow meter
Pump
Basics of electricityTypes of loads - (Resistor,inductor& capacitor)
Resistive load - In DC circuit (fig) the voltage and current
waveforms are straight lines because voltage is
constant.
- In AC circuit with pure resistance,voltage and current
are always in phase.
- Power consumed in DC circuit is constant as
voltage and current are constant.
- An AC ckt. that has only resistance produces a
positive power curve.
Basics of electricityTypes of loads - (Resistor,inductor& capacitor)
Resistive load - In DC circuit (fig) the voltage and current
waveforms are straight lines because voltage is
constant.
- In AC circuit with pure resistance,voltage and current
are always in phase.
- Power consumed in DC circuit is constant as
voltage and current are constant.
- An AC ckt. that has only resistance produces a
positive power curve.
Basics of electricity
Inductive load - An inductor is a coil of wire. A common inductive
load is an electric motor.
- Current lag behind voltage by 900 since voltage
is max at 900 while current is zero.
- Produce both positive and negative power. These
powers are equal in amplitude so their sum will
equal to zero.
- The inductor does not use real power still generator
supply it with voltage and current .
- So efficiency is lowered.
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Basics of electricity
Capacitive load- A capacitor opposes change in voltage.
- Current lead voltage by 900 since voltage across it
is zero and the current is maximum.
- Produce both positive and negative power. These
powers are equal in amplitude so their sum will
equal to zero.
- The capacitor does not use real power still generator
supply it with voltage and current .
- So efficiency is lowered.
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