CERTIFICATE

TO WHOM IT MAY CONCERN

Certified that the Physics Project has been prepared and
submitted by Abhigyan Kashyap , student of class XII,
Science Stream, Maharishi Vidya Mandir, Barsajai from
her actual knowledge which she gained while preparing
the project under my supervision. She has fulfilled the
criteria and hence completed the project.

SIGNATURE
(Teacher In charge)
PHYSICS DEPARTMENT
 ACKNOWLEGMENT
I take the opportunity to convey my heartfelt thanks to
Mr. Geetika and Mrs. Soma Sarkar, teachers of the
Department of Physics for their valuable suggestions and
support.
My sincere thanks goes to my parents who helped me in
completion of my project by providing me with necessary
information and support.
My sincere thanks also goes to The Principal, Maharishi
Vidya Mandir, Barsajai , In Charge of the Senior
Secondary Section,and my classmates for their
encouragement and help.
Lastly, I am thankful to our Lab Assistant, Department Of
Physiscs Mr. Khagen Das for his constant help in
completion of the project.
NAME: Abhigyan Kashayp
CLASS:XII
ROLL NO: 1
 CONTENT

 Aim
 Introduction
 Theory Involved
 Materials Required for Construction
 Circuit Diagram
 Working Of The Circuit
 Rectified DC Voltage
 Results
 Application
 Conclusion
 Aim

To construct a full wave rectifier and show that

the Alternating Components are rectified into a
direct current.
 Introduction

A full wave rectifier is a device which is used to rectify all the

alternating current components in an alternating supply and
make it purely a direct current. The two alternating halves of an
alternation current are rectified in a full wave rectifier which is
an advantage over a half wave rectifier. Most electronic devices
cannot withstand very high voltage or alternating current due to
its intense high power. The use of batteries in all devices is not
practical as their replacement and durability is a huge problem
as the device has to be dismantled each time for such a
replacement. So these rectifiers are used in most of the
electronic devices like TV’s, Radios, Chargers, Lightings etc.
There are several stages in a rectifier. Based on their
rectification they are classified into two. The single staged &
multi staged.
In the multi staged rectifiers, more than two diodes are used and
these are used in the above-mentioned devices. The singled
staged rectifier has only 2 diodes, the one we are to discuss in
this project. The multi diode rectifier has only 2 diodes, the one
we are to discuss in this project. The multi diode rectifiers has
an efficiency ~ 94.6% while that of the single is only 81.2%.
 Theory involved

The Following Explains the functioning of a full wave rectifier.

Working of a full wave rectifier
 A step-down transformer is used in order to step down or
decrease the high voltage AC into low voltage AC.
 The transformer’s secondary winding is connected to the
opposite points of the bridge made up diodes. The
secondary output of the transformer is connected at a point
where both the anode as well as the cathode of the diode
lies.
 All the four diodes are connected in such a way that they
form a passage which allows only one side of the AC
voltage or pulse and converts the negative part of it into
positive voltage or pulse.
 The DC voltage output of the bridge rectifier circuit is
obtained from the points where both the diodes are
connected either from anode or cathode. The anode
becomes the positive part as well as cathode becomes the
negative part of the DC voltage output
 The output voltage of the bridge rectifier is not a
constant/straight DC voltage but does have a pulse which is
 then reduced with the help of an electrolytic capacitor
which acts as a filter to Pulsated DC voltage.
 The efficiency of the bridge rectifier lies in how the
minimum amount of pulse it has after the filter is applied to
the pulsated output.
 The full-wave Bridge Rectifier Circuit is complete as the
capacitor or a filter is applied to decrease the pulse and the
voltage is then used for various purposes.
Full Wave Bridge Rectifier Circuit Theory Explained

The working of the full-wave Bridge Rectifier Circuit is divided

into two cycles which are then filtered in order to reduce the
pulse or the repel on the DC voltage.
The two cycles of the Full-wave bridge rectifier are classified
below:
1. First half cycle
2. Second half cycle
Full Wave Bridge Rectifier characteristics
First half cycle

 The output voltage of the secondary winding of the

transformer is in the first half of the wave that is the
positive side of the AC voltage.
 In this condition, two of the opposite diodes connected will
be in forward-bias and the current flows. The other two
opposite diodes connected in the circuit will be in reverse-
bias, so the current would not flow through those.
 During this cycle, the first half of the AC voltage is
obtained as a half positive pulse of our desired DC voltage.
  Until the first half cycle, the path of the current remains
from the anode of the first forward-biased diode to the
cathode of the another.
 As the output voltage of the transformer drops to the zero
voltage the first half cycle of the bridge rectifier circuit is
completed.
Second half cycle

 Second half-cycle works as the opposite of the first half

cycle.
 In the second half cycle of the output AC voltage from the
secondary winding of the transformer, the opposite diodes
are in forwarding bias (other than the diodes which are in
forwarding bias in the first half cycle).
 In the second half cycle, the negative part of the AC
voltage flows through the forward biased diodes leaving the
rest of the two in reverse bias which was forward biased in
the first half cycle.
 During the second half cycle, the path of the flow of current
becomes from the anode of the first forward-biased diode
to the cathode of the another, which ultimately follows the
same direction of current as it was in the first half cycle.
 During this cycle, the second half that is a negative part of
the AC voltage is obtained as another half positive pulse of
our desired DC voltage.
The two cycles that are the first and the second half cycle
combine and become a DC voltage.
However,
The generated DC voltage has a Pulse or ripple property which
makes it less useful when it comes to using it as a proper power
supply in various applications.
The remains of the pulse or ripple in the DC output of the full-
wave bridge rectifier bridge is then rectified with the help of a
capacitor.
After using the capacitor the ripple is reduced, the reduction of
ripple depends on the rating of the capacitor (in µF mostly) used
to filter the DC voltage.
Peak voltage is obtained and the output voltage is generated.
 Materials required in the
construction

Connecting wires, a plug, single lead wire - 2m, 3 – nuts & Bolts
of 2 to 3 cm length, Circuit board of mica, a small box to place
the model, a transformer, A capacitor, A Resistor (1 KΩ±5%),
P-N junction diodes, Insulation tape, Blades, soldering wax,
soldering lead, soldering iron & sand paper.
Details of the materials used :
i. Connecting wires and a plug
A normal insulated copper wire able to withstand 220 –
230 v is required.
ii. Single lead wire
Thin wire with one single strand of copper well Insulated
and able to conduct a current of 1 ampere or a D.C current
efficiently.
iii. A circuit board
A normal board of mica facilitated with clips to simplify
the connection.
 iv. Nuts ad bolt
In order to fix the board & transformer firmly.
Size- 2cm – 3 cm.
v. Soldering wax & lead
The wires are to be soldered firmly to make the connection
tight so for this a thin lead wire is required to affix the
connections and wax to make the lead to hold on when
soldered.
vi. A LED bulb
To test the output voltage whether Direct or not.
vii. A 9-0-9 transformer
Transformer is a device used to change the voltage of an
alternating current. The transformer which converts low
voltage to high voltage is called a step up transformer
whereas the one which converts high voltage to low
voltage is called a step down transformer. It consists of a
laminated core consisting of two coils, a primary & a
secondary coil. In a step up the number of turns in the
secondary is greater that that of the primary and the
reverse in a step down transformer. Here we use a step
down transformer which steps down 230V to 6V between
the secondary terminals and the center tap
viii. A Resistor
A resistor is an electronic components whose resistance
value tells us about the opposition it offers to the flow of
electric current. Resistance is measured in ohms (Ω).
We determine the value of a resistor using the colour
coding on the rings of the resistor –
 Black - 0
 Brown –1
 Red -2
 Orange – 3
 Yellow – 4
 Green - 5
 Blue - 6
 Violet - 7
 Grey - 8
 White - 9
Tolerance :
 Gold - ± 5%
 Silver - ± 10%
 Colourless - ± 20%

Measurement :
1st Colour - 1st digit
2nd Colour - 2nd digit
3rd Colour - Power to 10
4th Colour – Tolerance
For Eg: For a resistor of colour code – brown, black,
green & gold. The resistance value is 10×105 ±5%
 Here we use a single resistor of Brown, Red, Red &
Gold colour rings. Its Value = 12×102 ±5%
Resistance can be connected in 2 ways –
In series, R = (R1 + R2 + R3…..) & In Parallel R-1=(R1-
1
+R2-1+R3-1….)
ix. P-N junction Diodes
When one side of a semiconductor crystal (Germanium or
silicon) is doped with acceptor impurity atoms and the
other side with donor impurity atoms a P-N junction is
formed. It is also called a semiconductor or crystal diode.
When diffusion of the two regions occur a resultant
potential barrier is created between the two sides due to
migration of electrons and holes.
When the diode is connected with P side to positive
terminal of a battery & N side to –ve terminal it is said to
be forward biased & reverse biased when reversed. In
forward biasing the applied positive potential repels the
holes and turns a current is made to flow overcoming the
Internal potential Barrier. While in reverse biasing the –ve
electrons 1st attract the holes and widen the Barrier and
then only the repulsion between the inner electrons occur
and current flows. So theoretically no current flows
through due to the widening of the Potential barrier but
practically a very small current does flows through.
Different types of diodes are present –
1. Zener diode
 2. P-N junction diode
3. LED
4. LAD
5. Solar cell
Here we use a P-N junction diode. The grayish ring
indicated the N side and the Black colouration the P side.
x. Finally, small equipments such as a soldering iron to
solder the lead, Blades, holders, insulation tapes – to
insulate the wire from shocking and sand paper – to rub
the oxidized wire ends are used.
CIRCUIT DIAGRAM
 WORKING

1st when the A.C. is supplied to the transformer, it steps down

the 220V main supply to 9V-6V. It has a capability of delivering
a current of 500mA. The 6V A.C. appearing across the
secondary is the RMS value. During the 1st half cycle of the
A.C. input Diode D1 is forward biased and a current ‘I’ flows in
the circuit in the direction AMLC. During this time diode D2 is
reverse biased. So it does not conduct any electric current due to
the high resistance offered during this reverse biased state .
During the next half cycle the diode D2 is forward and D1 is
reversed. Hence D2 conducts current in the direction BMLC and
D1 does not conduct any current. In subsequent half cycles of
the A.C current the above processes are repeated. In both the
half cycles it is clear that current flows through the resistor in
only one direction ML. Even though the voltage across RL is
unidirectional it will still contain a few A.C components. A
resistor is then used to adjust the output voltage. We can then
test the Output Voltage using a multi-meter.
Efficiency of Rectification
η= D.C power output ÷Total A.C input power
For a half wave rectifier,
η ~ 0.406 = 40.6 %
For a full wave rectifier, the one used here is
η ~ 0.812 = 81.2 %
By the use of more number of diodes the efficiency can be
increase to a maximum of 94.6%. Here we only use 2 diodes.
The use of multiple capacitors also nearly filters all A.C
components from the supply and resistance is adjusted for the
required output. As this is a simple circuit, only one is being
used, hence there will be slight factor of A.C. current still left in
the output but it is negligible.
RECTIFIED D.C VOLTAGE

Here in the above graph:

 The first graph represents the variations of the input A.C.
current.
 The second graph represents the variations of the current
through the circuit during the positive half cycle (let us
consider the case when current flows through D1).
  The third graph represents the variations of the
current through the circuit during the negative half cycle
(let us consider the case when current flows through D2).
 The forth graph represents the overall variations of the
flow of current in the circuit.

RESULT

A full wave rectifier is a very usesfull device for converting high

voltage A.C. current into low voltage D.C. current which is
necessary for functioning of electrical appliences like television
, refrigerators, mobile phones, etc.
 APPLICATION

The applications of a full wave rectifier are:

 Car alternator
 Any cell phone charger
 Laptop/tablet charger
 Power bank
 Any other switching supply: alarm, charger, Bluetooth
device charger, LAN or router supply etc
 Audio power supply in pre amp and power amplifier
 Any video device
 Lead battery charger
 LED driver, any LED lamp over 10 watts in general
 CONCLUSION

This project helped me a lot in understanding the working and

the functioning of a full wave rectifier. It has also helped me in
understanding the constituents and the components and their
function in general and in respect to this circuit . This will
certainly help me in future and has provided knowledge
regarding a full wave rectifier From this project I have gained a
lot of knowledge about different components of the circuit,
rectification process in general and different stages of
rectification and its uses. During the making of this project I
came across many different components and their functioning an
many different concepts came to know about their uses and
results. The project was of great way to gain knowledge.