Class 12 physics project on full wave bridge rectifier

SRDAV Public School Class-XII Physics Project Report Topic – Full Wave Bridge Rectifier Submitted to: Mrs. P. Tiwari Submitted by: Vaibhav Pal

Acknowledgement I would like to express my special thanks of gratitude to my physics teacher (Mrs. P. Tiwari) who gave me the golden opportunity to do this wonderful project on the topic (Full wave bridge rectifier), which also helped me in doing a lot of Research and i came to know about so many new things I am really thankful to them. Secondly I would also like to thank my parents and friends who helped me a lot in finalizing this project within the limited time frame.

Certificate This is to certify that Vaibhav Pal (Roll No: ) student of class XII , SRDAV Public School has completed the project titled “Full Wave Bridge Rectifier” during the academic year 2014 -15 towards partial fulfillment of credit for the Physics Project evaluation of AISSCE 2015, and submitted working model and satisfactory report , as compiled in the following pages, under my supervision.

Mrs. P. Tiwari (Teacher’s signature)

Contents         

Aim Theory Materials required Circuit diagram Working Graph Applications Merits and Demerits Bibliography

Aim To construct a full wave bridge rectifier and show that that Alternating Current is rectified into a Direct Current.

Theory The process of converting AC (which periodically reverses direction) current into DC (which flows only in one direction) current is known as Rectification. The electrical device used to so is known as Rectifier. Rectifiers have many uses, but are often found serving as components of DC power supplies and high-voltage direct current power transmission systems. Rectification may serve in roles other than to generate direct current for use as a source of power. The simple process of rectification produces a type of DC characterized by pulsating voltages and currents (although still unidirectional). Depending upon the type of end-use, this type of DC current may then be further modified into the type of relatively constant voltage DC characteristically produced by such sources as batteries and solar cells. A diode bridge is an arrangement of four (or more) diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input. When used in its most common application, for conversion of an alternating current (AC) input into a direct current (DC) output, it is known as a bridge rectifier. A bridge rectifier provides full-wave rectification from a two-wire AC input, resulting in lower cost and weight as compared to a rectifier with a 3-wire input from a transformer with a center-tapped secondary winding.

Materials Required Connecting wires Step-down transformer Diodes (4) Capacitor (1) LED (1)

Circuit Diagram

Working Initially when the A.C. is supplied to the transformer, it steps down the 220V main supply to 6 volts. It has a capability of delivering a current of 500mA. The 6 volts A.C. appearing across the secondary coil is the RMS value and the peak value is 8.4 volts. During the Ist half cycle of the A.C. input Diode D1 is forward biased and a current ‘I’ flows in the circuit in the direction ABCDEFGHIJKLM. During this time diodes D2 and D3 are reverse biased. So they do not conduct any electric current. During the next half cycle the diode D2 is forward and D1 is reversed. Hence D2 conducts current in the direction MLKJCDEFGHIA 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 LED in only one direction. Even though the voltage across LED is unidirectional it will still contain a few A.C components. This is filtered and made smooth using a capacitor, which filters 99% of the A.C current.

Capacitor nearly filters all A.C components from the supply. But there will be slight factor of A.C. current still left in the output but it is negligible. The output Direct Current and voltage light up the LED.

Graph

Applications  Because of their low cost compared to center tapped they are widely used in power supply circuit.  This can be used to detect the amplitude of modulated radio signal.  Bridge rectifiers can be used to supply polarized voltage in welding.  In daily life, rectifier find use in mobile chargers.

Merits and Demerits Merits: The rectification efficiency of full-wave rectifier is double of that of a half-wave rectifier.  The ripple voltage is low and of higher frequency in case of a full-wave rectifier so simple filtering circuit is required.  Higher output voltage higher output power and higher TUF in case of a full-wave rectifier.  In a full-wave rectifier, there is no problem due to DC saturation of the core because the DC currents in the two halves of the transformer secondary flow in opposite directions.

Demerits: Full-wave rectifier needs more circuit elements and is costlier.

Bibliography  Physics – Textbook for class XII (NCERT)  Laboratory Manual of Physics  Encyclopedias Websites: www.google.in  www.wikipedia.org  www.youtube.com