OHM’S LAW FOR DC
THE TEMPERATURE REMAINING CONSTANT THE
CURRENT FLOWING IN THE CIRCUIT IS DIRECTLY
PROPORTIONAL TO THE APPLIED VOLTAGE AND
INVERSELY PROPORTIONAL TO ITS RESISTANCE.
V=IXR
I = V/R
R = V/I
NUMERICALS BASED ON OHM’S LAW
IF
V=
I=
V/R = 9/10 = 0.9 AMPERE
IF
I = 10 AMPERE
R = I/V
IF
9 VOLT AND
V = 10 VOLT
= 10 / 10 = 1 OHM
I = 10 AMPERE
V=I*R
R = 10 OHMS
R = 5 OHMS
= 10 * 5 = 50 VOLT
KIRCHHOFF’S FIRST LAW
THE TOTAL CURRENT ENTERING THE CUIRCUIT
(FLOWING TOWARDS) IS EQUAL TO THE TOTAL CURRENT
LEAVING THE CUIRCUIT.
KIRCHHOFF’S SECOND LAW
THE TOTAL VOLTAGE DROP ACROSS THE RESISTANCE OF
A CLOSED CIRCUIT IS EQUAL TO THE TOTAL VOLTAGE
APPLIED TO THE CIRCUIT.
DIAGRAM KIRCHHOFF’S FIRST LAW
DIAGRAM KIRCHHOFF’S SECOND LAW
POTENTIAL DIFFERENCE
IT IS THE AMOUNT OF THE WORK DONE IN
BRINGING ONE UNIT OF POSITIVE CHARGE
FROM ONE POINT TO ANOTHER IN THE
ELECTRIC FIELD.
THE VOLTAGE RATING IS MEASURE OF
PRESSURE.
THE AMOUNT OF PUSH BEHIND ELECTRIC
CURRENT (EMF).
UNIT IS VOLT
AMPERE
THE RATE OF FLOW OF ELECTRON EQUAL TO
ONE COULOMB PER SECOND.
AMPERE IS UNIT OF CURRENT.
ELECTRIC POWER (WATT)
WHENEVER ELECTRIC CURRENT FLOWS WORK IS DONE
IN MOVING THE ELECTRONS THROUGH THE
CONDUCTOR.
THE RATE AT WHICH THE WORK IS DONE IS CALLED
POWER. THE BASIC UNIT OF POWER IS WATT.
P=VXI
OR
P=IXIXR
1000 WATT = 1 KILO WATT ( ONE UNIT OF ELECTRICITY IS
1 KW HR )
ONE HORSE POWER = 746 WATTS. ( ENERGY REQUIRED
TO LIFT 33000 POUNDS OF WEIGHT TO 1 FEET OF HEIGHT
AND KEEP IT THERE FOR 1 MIN.
WATT and DECIBEL
1dB
=
10 Log WATT
CONVERTING 100 WATT INTO DECIBELS
100 WATT
= (10 log 100) dB
= 10 *2
= 20 dB
100 WATT = 20 dB, 1000 WATT = 30 dB
JOULE: UNIT OF WORK. ENERGY SPENT
IN ONE SECOND BY AN AMPERE FLOWING
THROUGH ONE OHM.
ENERGY:
THE STRENGTH OR
CAPACITY REQUIRED TO DO WORK.
POWER MEASURED OVER A TIME (KW HR)
RESISTANCE
RESISTANCE IS THE OPPOSITION OFFERED BY A
MATERIAL TO THE FLOW OF ELECTRON.
IN A CIRCUIT RESISTANCE IS USED TO REGULATE
FLOW OF CURRENT AND ALSO TO GENERATE
HEAT AND LIGHT AT CERTAIN OCCASION
THE UNIT OF RESISTANCE IS OHMS.
1000 OHMS = 1 KILO OHMS
1 AMPERE = 1000 MILI AMPERE
1 MICRO VOLT = 1/1 000 000 VOLT
RESISTANCE COLOUR CODE AND CIRCUIT SYMBOL
RESISTANCE COLOUR CODE AND CIRCUIT SYMBOL
RESISTANCE COLOUR CODE
B
B
R
O
Y
G
B
V
G
W
BLACK
BROWN
RED
ORANGE
YELLOW
GREEN
BLUE
VOILET
GREY
WHITE
=
=
=
=
=
=
=
=
=
=
0
1
2
3
4
5
6
7
8
9
B B ROY GREAT BRITAIN VERY GOOD WIFE
FIRST AND SECOND COLOUR ARE DIGITS.
THIRD COLOUR IS NO OF ZEROS
FOURTH COLOUR IS TOLERANCE
RESISTANCE COLOUR CODE
B
R
Y
B
G
BLACK
RED
YELLOW
BLUE
GREY
=
=
=
=
=
0
2
4
6
8
B
O
G
V
W
BROWN
ORANGE
GREEN
VOILET
WHITE
=
=
=
=
=
1
3
5
7
9
FOURTH COLOUR IS TOLERANCE
GOLD = 5%
SILVER = 10%
NO COLOUR = 20%
31 OHMS= FIRST COLOUR WILL BE ORANGE
SECOND COLOUR WILL BE BROWN
THIRD COLOUR WILL BE BLACK
RESISTANCDE IN SERIES
R = R1 + R2 + R3
RESISTANCDE IN PARALLEL
1/R = 1/R1 + 1/R2 + 1/R3
NUMERICALS : RESISTANCE
IF
R1 = 20 OHMS
R2 = 30 OHMS
R1 = 40 OHMS
IN SERIES
R = R1 + R2 + R3
R = 20 + 30 + 40 = 90 OHMS
IN PARALLEL
1/R = 1/R1 + 1/R2 + 1/R3
1/R = 1/20 + 1/30 + 1/40 = 6/120 + 4/120 + 3/120 =
13/120
R = 120/13 = 9 OHMS APPROX
An RLC circuit (also known as a resonant circuit, tuned circuit, or LCR circuit) is an electrical circuit consisting of a resistor (R), an inductor (L), and a capacitor (C), connected in
series or in parallel. This configuration forms a harmonic oscillator.
Tuned circuits have many applications particularly for oscillating circuits and in radio and communication engineering. They can be used to select a certain narrow range of
frequencies from the total spectrum of ambient radio waves. For example, AM/FM radios typically use an RLC circuit to tune a radio frequency. Most commonly a variable capacitor
allows you to change the value of C in the circuit and tune to stations on different frequencies. Other practical designs vary the inductance L to adjust tuning.
An RLC circuit is called a second-order circuit as any voltage or current in the circuit can be described by a second-order differential equation for circuit analysis.
Series RLC with Thévenin power source
In this circuit, the three components are all in series with the voltage source.
Series RLC Circuit notations:
V - the voltage of the power source (measured in volts V)
I - the current in the circuit (measured in amperes A)
R - the resistance of the resistor (measured in ohms = V/A);
L - the inductance of the inductor (measured in henrys = H = V·s/A)
C - the capacitance of the capacitor (measured in farads = F = C/V = A·s/V)
q - the charge across the capacitor (measured in coulombs C)
Given the parameters v, R, L, and C, the solution for the charge, q, can be found using Kirchhoff's voltage law. (KVL) gives
For a time-changing voltage v(t), this becomes
Parallel RLC circuit
Parallel RLC Circuit notations:
V - the voltage of the power source (measured in volts V)
I - the current in the circuit (measured in amperes A)
R - the resistance of the resistor (measured in ohms = V/A);
L - the inductance of the inductor (measured in henrys = H = V·s/A)
C - the capacitance of the capacitor (measured in farads = F = C/V = A·s/V)
The complex admittance of this circuit is given by adding up the admittances of the components:
OHM’S LAW FOR AC
IMPEDENANCE DESCRIBES A MEASURE OF
OPPOSITION TO ALTERNATING CURRENT.
IT IS COMBINATION OF RESISTANCE, CAPACITIVE
REACTANCE AND INDUCTIVE REACTANCE
IT CAN BE CALCULATED BY OHM’S LAW
I = E/Z
OHM’S LAW FOR AC
RESONANCE IS A SPECIAL FREQUENCY IN AC CIRCUIT
DETERMINED BY VALUE OF RESISTANCE , CAPACITANCE
AND INDUCTANCE.
IN SERIES RESONANCE IS GIVEN BY MINIMUM
IMPEDENCE AND ZERO PHASE.
IN PARALLEL ROSONANCE IN MAXIMUM, WHEN
INDUCTANCE AND CAPCITANCE ARE EQUAL AND 180 OUT
OF PHASE.
IT CAN BE CALCULATED BY
F = ½ PI UNDERROOT LC
IMPEDENANCE DESCRIBES A MEASURE OF
OPPOSITION TO ALTERNATING CURRENT
IT IS COMBINATION OF RESISTANCE,
CAPACITIVE REACTANCE AND INDUCTIVE
REACTANCE
IT CAN BE CALCULATED BY OHM’S LAW
I = E/Z
FUSE
IT IS CURRENT RATED.
IT IS INSERTED BETWEEN ELECTRICAL SUPPLY AND
EQUIPMENT TO PROTECT IT FROM GETTING DAMAGED.
IF CURRENT FLOW IN THE CIRCUITS EXCEEDS THE
RATING. IF EQUIPMENT NEEDS 500 M A FUSE ( ½ A) IS
INSERTED.
CIRCUITS BREAKER ARE ALSO USED AS PROTECTION
FROM OVER LOADS. IF CURRENT INCREASES, IT JUMPS
AND BREAKS THE CIRCUIT.
CELL

CELL IS A DEVICE WHICH CONVERTS CHEMICAL
ENERGY INTO DIRECT CURRENT

COMBINATION OF CELLS IS KNOWN AS BATTERY

CELLS CAN BE CONNECTED IN SERIES OR
PARELLEL

SERIES : VOLTAGE ADDS UP CURRENT
REMAINS THE SAME

PARALLEL : CURRENT ADDS UP VOLTAGE
REMAINS THE SAME
RATING OF A BATTERY

BATTERIES ARE RATED IN AMPERE HOUR (AH)

5 AH BATTERY CAN GIVE CURRENT OF 1 AMPERE
FOR 5 HOURS OR 5 AMPERE FOR 1 HOUR. BUT IT
CAN NOT GIVE 10 AMPERE FOR HALF HOUR DUE
TO BATTERY INTERNAL RESISTANCE
CIRCUIT DIAGRAM CELL
TYPES OF CELLS : PRIMARY

DRY CELLS ARE KNOWN AS PRIMARY CELLS

VOLTAGE IS 1.5 VOLT (ONE TIME USE TYPE)

CARBON ROD IS +VE

CONTAINER IS ZINC –VE

AMMONIUM CHLORIDE IS ELECTROLYTE

ADVANTAGE : CHEAP TO MASS PRODUCE

DISADVANTAGE : CAN NOT BE RECHARGED AND IF
LEFT UNUSED FOR SOME TIME, IT DETORIATES
CELLS : SECONDARY CELL

SECONDARY CELLS CAN BE RE CAHRGED

TWO TYPES OF SECONDARY CELLS ARE

LEAD ACID

NICKEL CADMIUM
SECONDARY CELLS : LEAD ACID

VOLTAGE IS 2 VOLT

LEAD PEROXIDE IS +VE

LEAD OXIDE IS –VE

DILUTED SULPHURIC ACID IS ELECTROLYTE

SPECIFIC GRAVITY WHEN CHARGED 1.25 TO 1.35

SPECIFIC GRAVITY WHEN DISCHARGED FALLS TO
1.17.

SPECIFIC GRAVITY IS MEASURED BY HYDROMETER

TOPPING UP IS DONE BY DISTILLED WATER
LEAD ACID : ADVANTAGE / DISADVANTAGE

ADVANTAGE


CAN BE RECAHRGED
DISADVATAGE

BATTERIES DISCHARGES IF KEPT
UNUSED FOR A
LONG TIME

CHARGING HAS TO BE CAREFULLY MONITORED BY
CHECKING VOLTAGE AND SPECIFIC GRAVITY

OVERCHARGING IS A PROBLEM

BOTH VOLTAGE AND SPECIFIC GRAVITY IS CHECKED
FOR DETERMINING IF A BATTERY IS DISCHARGED.
SECONDARY CELLS : NICKEL CADMIUM

VOLTAGE IS 1.2 VOLT UNDER VARYING
LOAD

NICKEL HYDROXIDE IS +VE

CADMIUM IS –VE

POTTASIUM HYDROXIDE (KOH) IS
ELECTROLYTE
NICKEL CADMIUM : ADVANTAGE / DISADVANTAGE

ADVANTAGE
 RUGGED, NON SPILLABLE
 NOT DAMAGED IF UNUSED FOR A LONG TIME
 OVER CHARGING AND DISCHARGING DOES NOT
AFFECT MUCH

USED IN AIRCRAFT
INVERTOR

AN INVERTOR IS AN ELECTRONIC DIVICE TO
CONVERT DC TO AC

BATTERY POWER IS USED FOR EMERGENCY
SUPPLY

BATTERY OUTPUT WHICH IS DC IS CONNECTED
TO INVERTOR. THE OUTPUT IS FED TO
EQUIPMENTS
INDUCTOR

A COIL OF WIRE USED TO SUPPLY INDUCTANCE
IN THE CIRCUIT.

VOLTAGE WHICH IS GENERATED IS CALLED
INDUCED EMF

INDUCED EMF OPPOSES ANY CHANGE IN THE
CURRENT WHICH INDUCED IT.

UNIT IS HENRIES AND SYMBOL IS L

SERIES : L = L1 + L2 + L3

PARALLEL : L = 1/L1 + 1/L2 + 1/L3
INDUCTOR
INDUCTOR IN SERIES
L = L1 + L2 + L3
RESISTANCDE IN PARALLEL
1/L = 1/L1 + 1/L2 + 1/L3
NUMERICALS : INDUCTOR
IF
L1 = 20 HENERIES
L2 = 30 HENERIES
L1 = 40 HENERIES
IN SERIES
L = L1 + L2 + L3
L = 20 + 30 + 40 = 90 HENERIES
IN PARALLEL
1/L = 1/L1 + 1/L2 + 1/L3
1/L = 1/20 + 1/30 + 1/40 = 6/120 + 4/120 + 3/120 =
13/120
L = 120/13 = 9 HENERIES APPROX
CAPACITOR

TWO CONDUCTING PLATE SEPERATED BY
INSULATING MATERIAL (DIEELECTRIC)
CONSTITUTES A CAPACITOR

AC WILL FLOW NOT DC

UNIT IS FARAD

SERIES : 1/ C = 1/C1 + 1/C2 + 1/C3

PARALLEL : C = C1 + C2 + C3

IN VARIABLE AIR CAPACITOR AIR IS DIELECTRIC

F = 1 / 2R UNDER ROOT LC
NUMERICALS : CAPACITOR
IF
C1 = 20 FARAD
C2 = 30 FARAD
C1 = 40 FARAD
IN SERIES
1/C = 1/C1 + 1/C2 + 1/C3
1/L = 1/20 + 1/30 + 1/40 = 6/120 + 4/120 + 3/120= 13/120
L = 120/13 = 9 FARAD APPROX
IN PARALLEL
C = C1 + C2 + C3
L = 20 + 30 + 40 = 90 FARAD
DIODE
TRIODE
A triode is an electronic amplification device having
three active electrodes. The term most commonly
applies to a vacuum tube (or valve in British English)
with three elements: the filament or cathode, the
grid, and the plate or anode. The triode vacuum tube
is the first electronic amplification device.
TRANSISTOR : PNP & NPN
A transistor is a semiconductor device used to amplify and
switch electronic signals. It is made of a solid piece
of semiconductor material, with at least three terminals for
connection to an external circuit. A voltage or current applied to one
pair of the transistor's terminals changes the current flowing
through another pair of terminals. Because the controlled
(output) power can be much more than the controlling (input)
power, the transistor provides amplification of a signal. Some
transistors are packaged individually but many more are found
embedded in integrated circuits.
The transistor is the fundamental building block of
modern electronic devices, and its presence is ubiquitous in modern
electronic systems.
PNP
NPN
CATHODE RAY TUBE
TRANSFORMER

TRANSFORMER IS A DEVICE USED IN AN AC
CIRCUIT EITHER IN TO STEP UP OR STEP DOWN
THE VOLTAGE

FOR CHANGING VOLTAGE IN DC CIRCUIT CELLS
HAVE TO BE CONNECTED IN SERIES AND IN
PARALLEL

DUE TO THE EASE WITH WHICH AC VOLTAGE CAN
BE CHANGED, AC IS BEING ALL OVER THE WORLD

50 HZ IS USED IN DOMESTIC SUPPLY TO PREVENT
LINE LOSSES AND 400 HZ IS USED IN AIRCRAFT
TO REDUCE THE SIZE OF TRANSFORMER /CHOKES
GENERATORS / MOTORS

GENERATOR IS A MACHINE WHICH CONVERTS
MECHANICAL ENERGY INTO ELECTRICAL ENERGY
IS CALLED GENERATOR

A GENERATOR DESIGNED TO PRODUCE AC IS
CALLED AC GENERATOR OR ALTERNATOR

A GENERATOR DESIGNED TO PRODUCE DC IS
CALLED AC GENERATOR

COMMUTATOR IS USED TO CONVERT AC TO DC

MOTOR IS A MACHINE WHICH CONVERTS
ELECTRICAL ENERGY INTO MECHANICAL ENERGY
IS CALLED GENERATOR