I would like to thanks my Physics Teacher Mohammad Akram Sir for
giving the extraordinary idea about this project on the topic “ HALF
WAVE RECTIFIER “ and guiding this project until finish line. I
would also like to express my thanks to the principal Mrs. Neeru
Bhaskar for inspiring us on the project and encouraging us.
My thanks should not stop alone with teachers. My parents and
friends also played a big role in it. I see this project as a result of hard
work from us and innovation from my teachers. So, thanks to all of
them who put their hands in it and made it successful.
A rectifier is a simple diode or group of diodes which converts the
Alternating Current (AC) into Direct Current (DC).
We know that a diode allows electric current in one direction and
blocks electric current in another direction. We are using the principle
to construct various types of rectifiers
Rectifiers are classified into different types based on the number of
diodes used in the circuit or arrangement of diodes in the circuit. The
basic types of rectifiers are : half wave rectifier, full wave rectifier
and bridge rectifier.
5. A half wave rectifier is a type of a rectifier which converts the
positive half cycle (positive current) of the input signal into pulsating
DC ( Direct Current) output signal. The half wave rectifier is the
simplest form of the rectifier. We only use a single diode to construct
a half wave rectifier.
The half wave rectifier is made up of an AC source, transformer (step-
down), diode, and resistor (load). The diode is placed between the
transformers and resistors (load).
The half-wave rectifier circuit is made by using a semiconductor
diode (D) with a load resistance RL. The diode is connected in series
with the secondary of the transformer is being connected to the ac
The ac voltage across the secondary winding changes polarities after
every half cycle of input wave. During the positive half-cycles of the
input ac voltage i.e., when upper end of the secondary winding is
positive with respect to its lower end, the diode is forward based and
therefore conducts current. If the forward resistance of the diode is
assumed to be zero (in practice, however a small resistance exists) the
input voltage during the positive half-cycles is directly applied to the
load resistance RL, making its upper hand end positive with respect to
its lower end.
7. The waveforms of the output current and output voltage are of the
same shape as that of the input ac voltage.
During the negative high cycles of the input ac voltage i.e., when the
lower end of the secondary winding is positive with respect to its
upper end, the diode is reverse biased and so does not conduct. Thus,
during the negative half-cycles of the input ac voltage, the current
through and voltage across the load remains zero. The reverse current,
being very small in magnitude, is neglected. Thus, for the negative
half-cycles no power is delivered to the load.
Thus, the output voltage (VL) developed across load resistance RL is
a series of positive half-cycles of alternating voltage, with intervening
very small constant negative high voltage levels. It is obvious from
the figure that the output is not a steady DC, but only a pulsating DC
wave. To make the output wave smooth and useful in a DC power
supply, we have to use a filter across the load. Since, only half-cycles
of the input wave are used, it is called a half wave rectifier.
8. Output of half wave rectifier is not a constant DC voltage. In real life
applications, we need a power supply with smooth wave forms. In
other words, we desire a DC power supply with constant output
voltage. A constant output voltage from the DC power supply is very
important as it directly impacts the reliability of the electronic devices
we connect to the power supply.
We can make the output of half wave rectifier smooth by using a
filter (a capacitor filter or an inductor filter) across the diode. In some
cases an resistor-capacitor coupled filter (RC) is also used.
MEASUREMENT OF CURRENT USING
To determine the current by measuring voltage and
resistance using Halfwave Rectifier.
MATERIAL REQUIRED: -
Wires for Connection
I. Take a AC Supply and connect it to switch.
II. Connect the terminal part of the AC terminal to the P
part of the diode using wire.
III. Now connect the other part of the AC terminal to the
IV. Connect the n-part of the dipole to the capacitor.
V. Connect the both ends of a capacitor to the resistance
VI. Place a connection between voltmeter and resistance
box by joining the terminals of voltmeter.
VII. Now power on the switch and find out the resultant
voltage by changing the resistance box.
VIII. Calculate the current by measuring the mean voltage
and resistance using ohm’s law.
13. CALCULATIONS: -
Mean v = 0.7 + 1.1 + 1.4 + 1.6 + 1. 8 = 1.32 v
Mean R = 1 + 2 + 3 + 4 + 5 = 3 ohm
Current I = Mean V / Mean R
= 1.32 / 3
= 0.264 Ampere
The average current produced by the halfwave rectifier = 0.264
A half wave rectifier is rarely used in practice. It is never preffered as
the power supply of an audio circuit because of the very high ripple
factor. High ripple factor will result in noises in input audio signal,
which in turn will affect audio quality.
Advantage of a half wave rectifier is only that it is cheap, simple and
easy to construct. It is cheap because of the low number of
components involved. Simple because of the straight forwardness in
Measuring the mean current flow helps us to understand the amount
of AC current passed through the circuit.
15. PRECAUTIONS: -
Do not switch on the circuit before checking whether it is
correct or not.
The connection between voltmeter and resistance box should be
Connect all the wires properly, loose connection may end up in
failure of circuit.
Capacitor of less volt may be connected to the diode.
16. SOURCES OF ERROR: -
The p and n parts of the diode may be changed.
The wire connection may be loose.