CLASS 12 PHYSICS PROJECT - Measuring current using halfwave rectifier
Sl.No Content Page No
1 Acknowledgement 1
2 Introduction 2
3 Theory 4
4 Experiment 7
5 Observation Table 10
6 Result 11
7 Conclusion 12
8 Bibliography 13
I would like to thank the Physics Lab Teacher
Mrs.Nalini mam for giving the extraordinary idea
about this project and guiding this project until
finish line.We would also like to express our thanks
to our Physics Teacher Mrs.Sowmya mam for
getting this idea about this project and encouraging
Our thanks should not stop alone with
teachers.Our friends and parents even played a big
part in it.I see this project as a result of hardwork
from us and innovation from our teacher.So, we
once again thank all of them who put their hands in
it and made successful
A rectifier a simple diode or group of diodes which
converts the Alternating Current (AC) into Direct
We know that a diode allows electric current in one
direction and blocks electric current in another
direction. We are using this 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 and full wave
A half wave rectifier is a type of 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 use only a single diode to
construct the 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 transformer and
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 and the load resistance RL. The
primary of the transformer is being connected to the
ac supply mains.
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 w.r.t. its lower end, the diode is
forward biased 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 end positive w.r.t. its lower end. The
waveforms of the output current and output voltage
are of the same shape as that of the input ac voltage.
During the negative half cycles of the input ac
voltage i.e. when the lower end of the secondary
winding is positive w.r.t. 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 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
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 device 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.
• Resistance box
• Ac supply
• Wires for connection
i. Take a AC Supply and connect it to switch.
ii. Connect the terminal part of the AC to the p part of
the diode using wire.
iii. Now Connectthe other part of the AC terminal to the
iv. Connect the n-part of the diode to the capacitor.
v. Connect the both ends of a capacitorto the resistance
vi. Place a connectionbetween voltmeter and resitance
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. Calculatethe current by measuring the mean voltage
and resistance using ohm’s law.
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 Ampere.
A half wave rectifier is rarely used in practice. It is
never preferred 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 its
cheap, simple and easy to construct. It is cheap
because of the low number of components involved.
Simple because of the straight forwardness in circuit
Measuring the mean current flow helps us to
understand the amount of AC current passed through
DO NOT SWITCH ON THE CIRCUIT BEFORE
CHECKING WHEATHER IT IS CORRECT OR NOT
THE CONNECTION BETWEEN VOLTMETER AND
RESISTANCE BOX SHOULD BE MADE
CONNECT ALL THE WIRES PROPERLY. LOOSE
CONNECTION MAY END UP IN FAILURE OF
CAPACITOR OF LESS VOLT MAY BE
CONNECTED TO THE DIODE.
SOURCES OF ERROR:-
o The p and n parts of the diode may be changed.
o The wire connection may be loose.
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