# Physics Investigatory Project - Transformer

Kendriya Vidyalaya No.2, Naval Base, Kochi
21 de Sep de 2019
1 de 21

### Physics Investigatory Project - Transformer

• 2. Kendriya Vidyalaya Kanjikode Department of Physics CERTIFICATE This is to certify that Aravind Ravi, Althaf Younoos and Jishnu Rajan, students of class XII-B have successfully completed the research on the below mentioned project under the guidance of Mr. Sivadas (Subject Teacher) during the year 2019-20 in partial fulfillment of physics practical examination conducted by AISSCE, New Delhi. Signature of external examiner Signature of physics teacher
• 3. ACKNOWLEDGEMENT Primarily I would thank God for being able to complete this project with success. Then I would like to thank my physics teacher Mr. Sivadas, whose valuable guidance has been the ones that helped me patch this project and make it full proof success his suggestions and his instructions has served as the major contributor towards the completion of the project. Then I would like to thank my parents and friends who have helped me with their valuable suggestions and guidance has been helpful in various phases of the completion of the project. Last but not the least I would like to thank my classmates who have helped me a lot. Althaf, Aravind and Jishnu
• 4. INDEX 1. CERTIFICATE 2. ACKNOWLEDGEMENT 3. AIM OF PROJECT 4. INTRODUCTION 5. THEORY 6. APPARATUS REQUIRED 7. PROCEDURE 8. OBSERVATION 9. RESULT 10. CONCLUSION 11. PRECAUTIONS 12. SOURCES OF ERROR 13. BIBILIOGRAPHY
• 5. AIM OF THE PROJECT  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.  To find the efficiency of the self-made transformer
• 6. Introduction The transformer is a device used for converting a low alternating voltage to a high alternating voltage or vice-versa. A Transformer is based on the principle of mutual induction according to which, a change in magnetic flux linked with a coil induces an e.m.f in the neighboring coil. In a transformer, the electrical energy transfer from one circuit to another circuit takes place without the use of moving parts. A transformer which increases the A.C. voltage is called a Step-up Transformer and one which decreases the A.C. voltage is called a Step-down transformer. Transformer is, therefore, an essential piece of apparatus both for high and low current circuits.
• 7. Theory When an alternating voltage is supplied to the primary coil, it results in a changing magnetic flux, which induces A.C. Voltage in the secondary coil. In an ideal transformer, whole of the magnetic flux linked with primary is also linked with the secondary coil, and then the induced e.m.f. in each turn of the secondary coil is equal to that induced in each turn of the primary coil. Thus if Ep and Es are the instantaneous values of the e.m.f. induced in the primary and the secondary coils, Np and Ns are the no. of turns of the primary and secondary coils of the transformer respectively, and dф / dt = rate of change of flux in each turn of the coil, then we have Ep = -Np dф / dt _______________ (1) Es = -Ns dф / dt _______________ (2) The above relations are true at every instant, so by dividing (2) by (1), we get Es / Ep = Ns / Np ______________ (3) If the transformer is assumed to be 100% efficient (no energy losses), the input power is equal to the output power, and since P = IE, Ip Ep = Is Es _______________ (4)
• 8. Therefore, from (3) and (4) Ns / Np = Es / Ep = Ip / Is = K Where, N is called Turn Ratio or Transformation Ratio
• 9. I. Step Up Transformer In a Step up transformer, low A.C. Voltage is converted to high A.C. Voltage. Here, the secondary coil has greater no. of turns (Ns > Np), but carries less current compared to primary (Is < Ip) Ns / Np > 1, i.e. Turn Ratio (K) is greater than 1 In order to transmit the voltage from the Power Plant or Generation Station over long distances, it is stepped up using a Step up Transformer. This voltage with increased levels is then transmitted to a distribution station. Illustration
• 10. II. Step Down Transformer In a Step down transformer, high A.C. Voltage is converted to low A.C. Voltage. Here, the secondary coil has lesser no. of turns (Ns < Np), but carries more current compared to primary (Is > Ip) Ns / Np < 1, i.e. Turn Ratio (K) is less than 1 At the distribution station, the high voltage from power station is reduced using a Step down Transformer. The voltage with decreased level is then made ready for consumer use. Illustration
• 11. III. Efficiency Efficiency of a transformer is defined as the ratio of output power to the input power. i.e. η = output power / input power = Es Is / Ep Ip Thus in an ideal transformer, where there is no power losses, n=1 But in actual practice, there are many power losses; therefore the efficiency of transformer is less than one.
• 12. IV. Energy Loses Following are the major sources of energy loss in a transformer: 1. Copper loss: Energy loss in the form of heat in the copper coils of a transformer. This is due to joule heating of conducting wires. 2. Eddy Current: Energy loss in the form of heat in the iron core of the transformer. This is due to formation of eddy currents in iron core. It is minimized by taking laminated cores. 3. Leakage of magnetic flux occurs in spite of best insulations. Therefore, rate of change of magnetic flux linked with each turn of secondary is less than the rate of change of magnetic flux linked with each turn of primary. 4. Hysteresis loss: Loss of energy due to repeated magnetization and demagnetization of the iron core when A.C. is fed to it. 5. Magneto striation i.e. humming noise of a transformer
• 13. V. Uses of Transformers  1. In voltage regulator for Television, Refrigerator, Computer, Air Conditioner etc. 2. A step down transformer is used for welding purposes. 3. A step down transformer is used for obtaining large current. 4. A step up transformer is used for the production of X- Rays and NEON advertisement. 5. Small transformers are used in Radio sets, telephones, loud speakers and electric bells etc. 6. Transformers are used in the transmissions of A.C. over long distances.
• 14. Apparatus Required : Iron Rod Copper Wire Voltmeter Ammeter
• 15. Circuit Diagram : 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.
• 16. 3. Connect primary 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 secondary and record the observations. 5. Now connect secondary to the A.C main, which now becomes a step up transformer, and again measure voltage and current through primary and secondary coil. 6. Repeat the above steps by changing the number of turns in primary and secondary coil.
• 17. Observation : Result  The ratio Ns / Np is equal to the ratios Es / Ep and Ip / Is  Turn Ratio, Ns / Np =  Efficiency = Sl. No. Np NS Turn Ratio K = Ns/Np Input Output Es / Ep Ip / Is Efficiency η = Poutput / Pinput Es Is / Ep Ip Voltage Ep Current Ip Power P=Ep Ip Voltage Es Current Is Power P=Es Is
• 18. Conclusion 1. The output voltage of the transformer across the secondary coil depends upon the ratio of the no. of turns (Ns / Np) 2. The ratio Ns / Np is equal to the ratios Es / Ep and Ip / Is 3. There is a loss of power between input and output coil of a transformer.
• 19. Precautions 1. All connection must be tight and proper. 2. While taking the readings of current and voltage the A.C should remain constant. Sources Of error 1. Values of current can be changed due to heating effect. 2. Eddy current can change the readings.
• 20. Bibliography 1) NCERT Textbook class 12 2) NCERT Physics Lab Manual 3) www.yahoo.co.in 4) www.scribd.com 5) https://www.electronicshub.org/step-down- transformer/