12 class Physics investigatory project on transformers.docx

CERTIFICATE This is to certify that this dissertation is a bonafide record of the project work done by ______________ of class XII (science) REG NO.______________ under my guidance and supervision in partial fulfillment of the requirements for appearing in AISSCE March 2014

Principal

External Examiner No____________

Teacher in Charge

INDEX             

Certificate Acknowledgement Introduction Objective Apparatus Circuit diagram Theory Procedure Observation Sources of error Precaution Conclusion Bibliography

ACKNOWLEDGMENT “ There are times when silence speak so much more louder than words of praise to only as good as belittle a person, whose words do not express, but only put a veneer over true feelings, which are of gratitude at this point of time.” I would like to express my sincere gratitude to my physics teacher Mr. Satheesh Kumar.B.S for his vital support, guidance and encouragement, without which this project could not have been completed. I would also like to express my gratitude to the staff of the department of physics of Jawahar Navodaya Vidyalaya Trivandrum for their support during the project.

INTRODUCTION The transformer is a device used for converting a low alternating voltage to a high alternating voltage or vice-versa.

OBJECTIVE To investigate the relation between the ratio of 1. Input and output voltage. 2. Number of turnings in the secondary coil and primary coil of a self made transformer.

APPARATUS Iron rod, copper wire of different gauge, two A.C voltmeter, and two A.C ammeters.

CIRCUIT DIAGRAM

THEORY The working of a transformer is based on mutual induction phenomenon. Let an ideal transformer in which the primary and secondary coil has negligible resistance and all the flux in the core links both primary and secondary windings. The induced emf in the primary coil Ep = Np dΦ/dt The induced emf in the secondary coil `

Es = Ns dΦ/dt

Where the Φ id the magnetic flux linke with each turn of the primary ab=nd secondary coil at a time t. Then Es/ Ep = Ns /Np = k = transformer ratio For an ideal transformation, there is no loss of energy, then Input power = Output power

IpEp2

PROCEDURE 1. Take thick iron rod and cover it with a thick paper and wind a large number of turns of thin Cu wire on thick paper (say 60). This constitutes primary coil of the transformer. 2. Cover the primary coil with a sheet of paper and wound relatively smaller number of turns (say 20) of thick copper wire on it. This constitutes the secondary coil. It is a step down transformer. 3. Connect p1, p2 to A.C main and measure the input voltage and current using A.C voltmeter and ammeter respectively . 4. Similarly, measure the output voltage and current through s1 and s2. 5. Now connect s1 and s2 to A.C main and again measure voltage and current through primary and secondary coil of step up transformer. 6. Repeat all steps for other self made transformers by changing number of turns in primary and secondary coil.

SOURCES OF ERROR 1. Values of current can be changed due to heating effect 2. Eddy current can change the readings

PRECAUTIONS 1. Keep safe yourself from high voltage 2. While taking the readings of current and voltage the A.C should remain constant.

CONCLUSION 1. The output voltage of the transformer across the secondary coil depends upon the ratio (Ns/Np) with respect to the input voltage 2. The output voltage of the transformer across the secondary coil depends upon the ratio (Ns/Np) with respect to the input voltage 3. There is a loss of power between input and output coil of a transformer.

BIBILOGRAPHY 1. NCERT Text book Class XII 2. Physics lab manuel. 3. Internet