ISC Sample Physics Project

TOPIC : VOLTAGE STABILIZER USING ZENER DIODE

INTRODUCTION :

Normally we use voltage stabilizers to provide a constant voltage from a d.c source across a load. Zener diode can be used as a voltage regulator.
A properly doped crystal diode, which has a sharp break down voltage, is known as zener diode. It is operated always under reverse bias condition in the breakdown region.
Zener breakdown takes place in very thin junctions. When both P and n regions are heavily doped, the depletion layer becomes very narrow. In a very thin depletion layer, the electric field across the depletion layer becomes as high as 107 Vm-1 with only small applied voltage. An electric field of such a high magnitude exerts a large force on the valence electrons of the atoms in the depletion layer. Consequently, covalent bonds are broken and as large number of electron-hole pairs are produced. These carriers are then accelerated by the applied voltage. Hence the reverse current increases rapidly. This process by which covalent bonds in the depletion region are directly broken by the strong electric field is called zener breakdown and the reverse voltage at which breakdown takes place is called zener voltage (Vz).


By the careful adjustment of the doping, the characteristic beyond the breakdown voltage is obtained almost vertical. In other words, in this region the reverse voltage across the diode remains almost constant for a large variation of reverse current. So the zener diode can be used as a voltage stabilizer. Therefore it is interesting to find the variation of output voltage on different input voltage in a voltage stabilizer.

AIM
To construct a voltage stabilizer and to study its characteristics.

METHOD OF STUDY
Connections are made as shown in figure.

Refer B L Theraja

R is the current limiting resistor, which keeps the current through zener diode within the permissible limit and RL is the load across which we get the regulated output. To make this connection, an external d.c source, a Rheostat, two voltmeters, a Zener diode, a Resistor and a key are needed.
The input (dc) voltage is applied to the zener diode.So that the diode is reverse biased.The voltage across RL will be always Vz, the zener voltage of the diode provided, the input voltage does not go below Vz, the zener voltage. Measurement of output voltage for different input voltages across the zener diode is taken.

COLLETED DATA
The output voltages across the zener diode for different input voltages are given below:
Zener voltage = 6 V
Resistance of the resistor= 330 ?

Table-1

From the above observation we could understand that the voltage across RL(Load) will be always Vz (here ˜6V) the zener voltage of the diode provided the input voltage does not go below Vz,the zener voltage. If input voltage is less than that of zener voltage, the output shows same voltage as in the input. But if input voltage is greater than that of Zener voltage, the output gives only zener voltage. So zener diode can be used as a voltage regulator to provide a constant voltage from a d.c source across a load RL.

* Suppose the input voltage Vi increases beyond Vz. Since the zener is in the breakdown region. The voltage across the zener diode and hence the output voltage across the load remains constant as Vz. The excess voltage, Vi-Vz. is dropped across the current limiting resistor R. if I is the current from the sources.
Vi- Vz = IR
To put it in another way, as Vi increases beyond Vz, I = IL + IZ increases. The zener will conduct the increase of current in I while the load current IL remains constant. Hence the output voltage across RL= I L X RL remains constant irrespective of the change in the input voltage Vi.

* Suppose the load resistance RL changes.then also the output voltage remains constant at Vz.

In the case if the load Rl increases, there is a decrease in the source current I at constant VI
It can be shown that the load current. IL decreases and the decreases is due to the decrease in the total current I and the increase in the zener current Iz. Thus the voltage across the load remains constant as VZ.

CONCLUSION

Voltage stabilizers (zener diodes) can be used as a voltage regulator to provide a constant voltage from a d..c source across a load RL.
By using voltage stabilizers, we can save our electrical equipments to a large extent. Because whenever the input voltage in the circuit increases, by thundering, short circuiting or by any other way, zener diode give only its zener voltage to the appliance as output voltage. Otherwise the appliances will burn out due to high voltage.

SUGGESTIONS

• Zener diode must be reverse biased.
• The depletion layer must be kept very thin.
• Zener diode must connect parallel to the load.
• By using voltage stabilizers in electrical appliances, we can save them to a large extent from thundering, short circuiting etc;-

REFERENCES

Fundamentals of PHYSICS CLASS XII BY Vas Publication.
Practical Physics class XI & XII by sunil A Pillai – An Anamika Publication.
NCERT Text of class XII.
Plus two physics S Chand and Co
Physics by Goyal
V K Mehta

Protect our educated youths.

Kerala Finance Minister Thomas Isaac in a statement said that the apprehensions being aired over the unification of retirement date for government employees were baseless.
I could not agree with him. Whatever be the minister’s claim there would be losses of increments and promotions to some sections of the employees. The pertinent point is Minister’s proposal of unification of retirement age to March 31 is a weird suggestion harming the prospects of the educated unemployed youths. The youths are being lost their opportunity for entry into service because of non-retirement in Government departments. It is a recurring complaint from the KPSC that many of the department vacancies are not reported in time by the Department heads and this approach will continue even after the fresh order from the Government for immediate report of vacancies.

Yet again extending service and all benefits at a higher rate to the existing senior employees will bring large financial burden to the State in the long run. A marginal gain of Rs 1000 crore in the current financial year by withholding pension payment of the employees would bring huge debt in years to come. . This would shake the financial stability of the State.

The youth organizations which are bound to oppose the unwarranted move of the Finance Minister are busy with other ridiculous matters such as shielding Mammootty in his shooting location elsewhere. It is now the duty of the media to put on focus that the youths get their due share in employment and in most cases it is only media that comes as a universal remedy for the affected.

For me it appears as a wonder that none in Kerala Cabinet care the educated youths. If pension payment is a colossal problem for the Government, then why can’t it issue ‘shoot at sight order’ on pensioners. Many of the decisions of the Finance Minster are bizarre and not in the true spirit of the progress of the State. My request is the Kerala government should collect opinions from wide cross-sections of the people in the State before implementing bizarre decisions of self proclaimed intellects.

K A Solaman

Parent-teacher counseling could avoid the worst.

Teachers are human, and sometimes will not be in the vein of certain students without a valid reason. This is same as love at first sight. Some teachers see the face of their students as their own children’s and some others see faces of their enemies in students. There may be psychological enlightenment in this phenomenon and in most cases students are the worst losers. However, occasionally the loss of the teacher is also heavy as that is what happened in the Delhi school where not only the teacher but the Headmaster also was suspended. The mental agony brought to them if they are true teachers who always delight in the progress of their student, is beyond any reckon. But ironically all are seen happy in criticizing the teacher. The sad demise of the student would have been averted if the teacher was given sufficient prior information about the health condition of the student. And in that case the responsibility of the parents cannot be ruled out.

Here in Kerala too punishment such as standing on sunlight or continuous running a kilometer was imposed, of course, not for class room lessons but for NCC. While I was a student in Pre-degree classes I noticed that if cadet did not turn out in time for parade he was asked to run a km with a heavy rifle in his hand. No one was spared from this punishment but none was seen annoyed as it was a part of that education.

Present day parents are very much concerned about their children. If a teacher in LP school asks a student to clean his teeth using mango tree leaf, as did in schools 30-40 years back, the parents will not tolerate the teacher. Time has changed and teachers’ job has become a dicey one. I could not blame that hapless teacher who imposed a past and crude punishment on her student taking her to death. The teacher might have been trying to pick up the child to progress but it ended in despair. The Delhi school incident is not an isolated case. To avoid replication parent-teacher counseling could be thought of in such situations. As practiced in NAAC accredited colleges health club can be formed in schools under the supervision of a teacher with skill in first aid treatment to avoid casualties.

K A Solaman

PET (Position Emission Tomography)

PET (Position Emission Tomography)

A brain imaging technique that maps active brain areas via an injection of 2-deoxyglucose, which emits positrons when taken up by actively metabolizing cells. During the test, the tracer liquid is put into a vein (intravenous, or IV) in your arm. The tracer moves through your body, where much of it collects in the specific organ or tissue. The tracer gives off tiny positively charged particles (positrons). The camera records the positrons and turns the recording into pictures on a computer.

PET scan pictures do not show as much detail as computed tomography (CT) scans or magnetic resonance imaging (MRI) because the pictures show only the location of the tracer. The PET picture may be matched with those from a CT scan to get more detailed information about where the tracer is located.

A PET scan is often used to find cancer, to check blood flow, or to see how organs are working.

www.ualberta.ca/~neuro/OnlineIntro/glossary.htm

Positron Emission Tomography (PET)
Positron emission tomography (PET) is a test that uses a special type of camera and a tracer (radioactive chemical) to look at organs in the body.

www.webmd.com/a-to-z-guides/positron-emission-tomography

K A Solaman
Saturday, March 28, 2009

Laughable coalition

Veteran CPI(M) leader Jyoti Basu has rightly expressed his doubts regarding the viability of a ‘Third Front’ Government at the Centre. The ‘Third Front’ is not a viable alternative to the Congress or the BJP because such a rag-tag coalition can collapse at any given time. So far the ‘Third Front’ has not projected anyone as its prime ministerial candidate, and will not do so until the general election is over. This delay only reflects the indecisiveness of the coalition, which is enough to discourage the electorate from voting it to power.

K A Solaman

KAS PHYSICS

Our distinguished teachers

Prof K A Solaman, M Sc, M Phil, M A(Dist Edcn), M A(Public Admin)
Former Head of the Department of Physics, St Michael's College, Cherthala and Faculty Member, College of Engineering, Cherthala

Prof K V Stella, Former Head of the Department of Physics, St Michael's College, Cherthala and Advocate, Cherthala

Mr K S Sibi M Sc and SRF

Ms K S Mary Linsa, II MSc

KASInstitute Plus 2 Physics Classes start on April 6, 2009

Ph 0478 2863483
Principal

Prof K A Solaman
(Former Head of the Deaprtment of PhysicsSt Michael's College, Cherthala )

PLUS II PHYSICS CLASSES START ON APRIL 6, 2009

Wednesday, March 04, 2009
KAS Physics and Electronics
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Near St Michael’s College, Cherthala
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Kerala, IndiaPin Code 688539,

Ph 0478 2863483
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PLUS II PHYSICS CLASSES START ON APRIL 6, 2009
Classes
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Principal

Prof K A Solaman
(Former Head of the Deaprtment of PhysicsSt Michael's College, Cherthala )
Posted by K A Solaman at 10:27 PM 0 comments

KAS Physics and Electronics

KASInstitute of Advanced Learning
Near Sty Michael’s College, Cherthala
Mayithara PO
Alappuzha Dt,
Kerala, IndiaPin Code 688539,

Ph 0478 2863483
E mail kasolaman@gmail.com

PLUS II PHYSICS CLASSES START ON APRIL 6, 2009
Classes
Plus Two(CBSE, HSC and ISC0Physics
B Sc Physics(Main and Sub)
BSc Electronics9Main and Sub)
B Tech Physics, Mechanics and Electronics and EM theory

Career Options
UGC-CSIR-NET
Principal

Prof K A Solaman
(Former Head of the Deaprtment of PhysicsSt Michael's College, Cherthala )

The shuttling decisions

The Sonia Gandhi headed AICC decided that Kerala Pradesh Congress Committee would decide the choice of its candidate to Rajya Sabha seat from Kerala and proposed two names-one is K Karaunakaran and other is Remesh Chennithala. What the octogenarian Karaunakaran is going to do other than to sleep all the time on the cushion seats in the house, is yet another question, the Kerala unit of the Congress, unable to take decision returned to the choice to Sonia herself. They authorised madam Sonia to nominate a candidate for the lone seat that the UDF can hope to win on the basis of its combined strength in the Assembly.

The KPCC is nowadays seen a little bigheaded as they have already confirmed that they would be the rulers of the State next time. The present ruling front headed by CPM has done enough harm to the state and they are in a desperate attempt to escape from the present muddle created by its leaders. The Marxist cadres are busy with smearing the posters of top leaders of the party with cow dung paints and almost lost in darkness. The Left Front sees no safe escape in the next election
Seeing this KPCC president Ramesh Chennithala decided to opt out from the Rajya Sabha race.. Last time Oommen Chandy was the CM and now being the President of the KPCC Chennithala sees a better prospect here. It is not always easy to bring back a Rajya Sabha member and ask him to become the CM of the state.

Gilani’s game of words.

Sir,
Pakistan Prime Minister Yusuf Raza Gilani plays the game of words by saying that file received from India on the Mumbai attacks is only“information” and not“evidence”. Evidently Gilani tries to wrap Pakistani links of the attackers. The distinction between the words information and evidence is therefore became a matter of discussion. Such a callous attitude from neighboring country's head may often prompt Indian counter-part to think about the adverse. Gilani’s proposals for conducting a joint investigation with India are unwarranted. However, one strongly feels that India should never enter into a war with Pakistan. The Samajwadi leader Amar Singh is seen immature in tackling a crucial situation.

The involvement of the Lashkar-e-Taiba, an extremist outfit, rooted in Pakistan in the Mumbai attacks has been internationally proved and accepted. The US and Britain emphasize it and hence it is now Pakistan’s job to act judiciously to avert a conflict between two countries.

K A Solaman

Flawed practice of Kerala University

Sir — The Union ministry of education has various schemes offering scholarships to needy students. But if they are not dispensed on time, what is the use of these scholarships? The postgraduate scholarship for rank-holders of all Indian universities for the academic session 2007-08 has been sanctioned by the University Grants Commission. The fund has been issued to the universities, and the awardees have been asked to contact the registrars of their respective institutions. However, the registrar of the University of Kerala seems reluctant to confirm when and how the students will receive the funds. As a guardian of one of the awardees, I got in touch with the registrar over this several times, but to no avail. I even submitted an RTI application enquiring about the process. In his reply to the RTI query, the registrar admitted that he has received the funds from the UGC but not the list of awardees. This is difficult to believe because the UGC is unlikely to send the funds without the list of the names of awardees. Moreover, the registrar has admitted that he knew that eight students would receive the scholarship for the given year from his university.

In fact, the registrar can easily find out who the awardees are by looking up the results of the concerned departments for the particular academic session. It is unfortunate that the toppers of a university recognized by the National Assessment and Accreditation Council are being mistreated by the institution that should have been proud of them.

K.A. Solaman

KAS Institute for Advanced Learning

Friday, June 16, 2006

KASInstitute of Advanced Learning
11th Mile Jn,
Mayithara POCherthala,
Alappuzha Dt,
Kerala, IndiaPin Code 688539,

Ph 0478 2863483
E mail kasolaman@gmail.com

Classes
B Sc Physics(Main and Sub)
BSc Electronics9Main and Sub)
Plus Two and ISC PhysicsMA Public Administration

Career Options
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BEd Entrance
Entrance Physics
Bank/PSC tests
Principal

Prof K A Solaman
(Former Head of the Deaprtment of PhysicsSt Michael's College, Cherthala )
posted by kas55 at 11:07 PM 0 comments