CLASS 12 PHYSICS PROJECT - Measuring current using halfwave rectifier
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The document describes an experiment to measure current using a half-wave rectifier. A student named Mathesh from VELS Vidhyashram School designed the experiment for their class 12 physics project. The experiment involves connecting a diode, capacitor, voltmeter and resistance box in a circuit to form a half-wave rectifier. By measuring the voltage output across different resistances and using Ohm's law, the average current of 0.264 Amperes was calculated. The summary concludes that a half-wave rectifier is rarely used in practice due to its high ripple factor but is cheap and simple to construct.
CLASS 12 PHYSICS PROJECT - Measuring current using halfwave rectifier
- 1. VELS VIDHYASHRAM SENIOR SECONDARY SCHOOL PHYSICS INVESTIGATORY PROJECT MEASURING CURRENT USING HALFWAVE RECTIFIER DONE BY NAME:-MATHESH.T CLASS:-XII-B ROLL NO:-12225
- 2. Index 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
- 3. 1 Acknowledgement 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 us. 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
- 4. 2 INTRODUCTION A rectifier 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 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 rectifier.
- 5. 3 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 resistor (load).
- 6. 4 THEORY 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
- 7. 5 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 rectifier.
- 8. 6 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.
- 9. 7 EXPERIMENT MEASUREMENT OF CURRENT USING HALFWAVE RECTFIER AIM:- To determine the current by measuring voltage and resistance using Halfwave Rectifier. MATERIAL REQUIRED:- • Diode • Capacitor(50v) • Voltmeter • Resistance box • Ac supply • Wires for connection
- 10. 8 PROCEDURE 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 Capacitor. iv. Connect the n-part of the diode to the capacitor. v. Connect the both ends of a capacitorto the resistance box. 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.
- 12. 10 OBSERVATION:- RESISTANCE(in ohm) VOLT(in V) 1 0.7 2 1.1 3 1.4 4 1.6 5 1.8
- 13. 11 CALCULATIONS:- Mean v=0.7+1.1+1.4+1.6+1.8 = 1.32 v 5 Mean R= 1+2+3+4+5 =3 ohm 5 Current I = Mean V / Mean R = 1.32 / 3 = 0.264 Ampere. RESULT:- The average current produced by the halfwave rectifier = 0.264 Ampere.
- 14. 12 CONCLUSION 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 design. Measuring the mean current flow helps us to understand the amount of AC current passed through the circuit.
- 15. 13 BIBILOGRAPHY http://www.physics-and-radio- electronics.com/electronic-devices-and- circuits/rectifier/halfwaverectifier.html http://www.electronics- tutorials.ws/diode/diode_5.html http://www.circuitstoday.com/half-wave- rectifiers GOOGLE IMAGES www.wikipedia.com NCERT Physics book Comprehensive Lab Manual
- 16. 14 PRECAUTIONS:- DO NOT SWITCH ON THE CIRCUIT BEFORE CHECKING WHEATHER IT IS CORRECT OR NOT THE CONNECTION BETWEEN VOLTMETER AND RESISTANCE BOX SHOULD BE MADE CORRECTLY . CONNECT ALL THE WIRES PROPERLY. LOOSE CONNECTION MAY END UP IN FAILURE OF CIRCUIT. 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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