Must Practice Questions for CBSE Physics CLASS 12: Solved

We will publish here the portions one cannot afford to miss while preparing for the CBSE class 12  Physics Examination

The Chapters will be posted below. On Clicking the name of the chapter a new page will open. On that page there will be a set of collected questions. On clicking the questions, the complete solution to the questions will open.

Please note that this system is under preparation. We hope to complete this within a month. The link will be activated only after completing the project.

1. ELECTROSTATICS


2. CURRENT ELECTRICITY


3. MAGNETIC EFFECTS OF CURRENT


4. ELECTROMAGNETIC INDUCTION


5. ALTERNATING CURRENT


6. ELECTROMAGNETIC WAVES


7. OPTICS


8. DUAL NATURE OF MATTER AND RADIATION


9. ATOMS AND NUCLEI


10. ELECTRONIC DEVICES


11. COMMUNICATION SYSTEMS

 

Eating food during Eclipse

I heard that we ought not eat anything in eclipse hours. Is there any scientific reason for that?

Tejaswini  asked

Answer:

There is no scientific reason behind it. Earlier it was thought that more harmful rays are reaching earth from sun at the time of eclipse. But actually it is less at the time of eclipse as they are blocked by moon coming in its path.

Irodov Solutions

After HC Verma, IE Irodov is the most sort after book by Physics lovers and Entrance aspirants of India. Whereas, Irodov is the most sought after by the rest of the world.

The following sites are providing free solutions to Irodov Solutions in Physics.

• http://irodovsolutions.blogspot.com/

DO you know any other site or source?

Post them here.

Why keeping a clean image on FaceBook is important?

Get admission for MBA through Facebook

Various MBA admission offices are visiting the facebook accounts of students to know more about them. Such admission offices discovered several things which negatively impacted the student candidacy. As many of the users don’t use privacy settings in Facebook, it may influence their academic as well as career pursuits.

Fake Business schools mushrooming in Delhi: AICTE

Fake business schools are mushrooming in Delhi which has been confirmed by AICTE. The capital has received a distinction in playing host to the largest number of illegal educational institutes in the country. AICTE has proved that as many as 75 institutes in Delhi are enrolling students under technical programmes without its approval.

AICTE and UGC keeping an eagle eye on Fake Educational Institutions

Stringent policies have been made by Government for fake educational institutions. AICTE and UGC are keeping an eagle eye on Fake Educational Institutions and the other unapproved institutions. Recently, UGC has identified 21 fake universities/institutions and AICTE had found 348 fake institutions in various parts of the country.

New Fee structure for IITs

Council of Indian Institute of Technology (IIT) has decided to hike the IIT fees by 400 percent. It will come into action from 2013 and it is for students who are not from economically and socially backward classes. But students will have to pay the extra fees once they get employed. At present, for Bachelors of Technology (B.Tech) course, students pay Rs. 50,000 annually and IIT Council has presented an agreement to increase the fees to Rs2 lakh per annum from 2013.

New Fee structure for IITs

Council of Indian Institute of Technology (IIT) has decided to hike the IIT fees by 400 percent. It will come into action from 2013 and it is for students who are not from economically and socially backward classes. But students will have to pay the extra fees once they get employed. At present, for Bachelors of Technology (B.Tech) course, students pay Rs. 50,000 annually and IIT Council has presented an agreement to increase the fees to Rs2 lakh per annum from 2013.

IIT JEE may be stopped!

The government has decided to scrap all the engineering exams from 2013-14. There will be a single common entrance test for engineering exams and there will be one merit list on the basis of which institutes including IITs will have to pick students. Students will also be counseled before they choose a course and this test will be similar to common entrance exams for medical courses beginning next year.

Sample Question Papers, Syllabus and Guidelines for Class IX and X for Term I (First Term September'2011)

Download and practice the following question papers to score well in the CBSE Summative Assessment 1

Force on a current carrying conductor

"if we are given an irregular shaped wire carrying current provided its cross sectional area is constant then we can find the net force on that conductor by joining the two ends of the conductor and thinking that joined part as a conductor and current should be flown in the same sequence then the force experienced by that conductor in magnetic field will give us the net force on that conductor. it is an easy method to find force on any shaped conductor........its my own theory with some examples too"

Vishal Kumar says

What do you think?

Post your responses as comments to this post

Latest CBSE Question Paper in Science for Class IX Summative Assessment

Download and practice the Science Question Papers for CBSE Class IX for Summative Assessment 1.

This question Paper is one among the many supplied by CBSE for conducting Summative Assessment 1 in schools.

Students are requested to upload the question papers once their exam are over using the contact form once their exams are over.

CBSE CLASS 9 SUMMATIVE ASSESSMENT –I (2011) SCIENCE

[embed]http://physics.2lv.in/wp-content/uploads/2011/09/IX_Sci.pdf[/embed]

WHAT IS PHYSICS?

The word physics is derived from the Greek words ‘physikos’ meaning “natural” and “physis” meaning nature. So we can say that physics is the study of the natural universe dealing with the fundamental constituents of the universe, the forces they exert on one another and the results produced by these forces.

The dictionary definition of Physics is “the study of matter, energy and the interaction between them”

In Physics we study a wide range of physical phenomena spanning all length scales: from subatomic particles from which all ordinary matter is made to the behavior of the material universe.

Physics doesn’t deal with just theoretical concepts. It is applied in every sphere of human activity.

Physics is basically a problem solving discipline. It solves not only the problems – numerical and conceptual in Physics but solves many problems of our life also. Just look around the many facilities we are enjoying- the television, DVD, speakers, computer… Most of them are because of Physics. Think of it.

PHYSICS is a dynamic and exciting field of science. It is not just a collection of independent ideas, but is really an interconnected whole.

Out of the other branches of science, Physics is the most basic science; not just a part of the Physical Sciences. An understanding of Science begins with an understanding of Physics.

“There is no field in Science that speaks more intimately than Physics, of man’s speculative inquiry into the natural world” – Frederick Seitz (Rockfeller University)

Physics can be enjoyable if it is understandable

Physics is a scientrific endeavour. It is a human activity in which new ideas are constantly being tried and in which scientific truth is never absolute.

Physics is the body of knowledge about nature that represents the collective efforts, findings, insights and wisdom of the human race. It is a human activity with the functions of discovering the orderliness of nature and finding the causes that govern this order.

Why students find Physics difficult?

Just have a look at the questions commonly discussed in Physics

How did the universe begin?

How will the universe change in coming days?

What keeps the sun shining?

……… And the list of questions is endless.

If these questions fascinate you, you will certainly like Physics.

Physics can be enjoyable if it is understandable

The main reason why students look upto physics with a sense of fear is mainly due to the fact that they fail to see the big picture. This in turn is due to the fact that they study Physics not as a whole but in small chunks and many cues to the puzzle are misplaced or forgotten. To appreciate the beauty a frequent look back is required to bring the pieces together.

The students in a hurry to score marks and to complete their task of preparing for exams, they fail to enjoy the beauty and flavor. To enjoy a gfame one must understand the rules governing the game.

Physics is all around us.

Physics deals with the laws governing the nature and to enjoy life and its various activities to its fullest we must know the laws and rules of nature as well as the nature of these laws.

And the interesting fact is that there are not too many laws.

Albert Einstein commented “The eternal mystery of the world is its comprehensibility”. This really explains the beauty of the subject, just by using a hand ful of laws we can explain the very many complex phenomena of the universe. Isn’t it fascinating? If your answer is yes, then you will really like physics, if not love it.

CBSE 12th Std Physics Numerical from Optics

A convex lens of crown glass(1.5) has a focal length of 15 cm. The lens is placed in (a) water(1.33) and carbon bisulphide(1,65).determine in each case whether the lens behaves as a conveging or a diverging lens and determine its focal length.

(Asked by Shobha)

Answer:

Formula used

For the lens to be converging, f must be positive and for it to be diverging, f must be negative

(a) In water the lens will be converging as the refractive index of glass is greater than that of  water.

(b) In Carbon disulphide the lens is diverging as the refractive index of glass is less than that of CS2

CBSE Physics MCQ for quick revision - Mechanics

• If the object is in equilibrium, the sum of all the forces acting on the object is zero.




1. Inertia


2. Force


3. Mechanical Equilibrium


4. Equilibrium rule

 

• A push or a pull on an object.




1. Inertia


2. Force


3. Mechanical Equilibrium


4. Equilibrium rule

 

• The tendency of objects to resist changes in motion.




1. Inertia


2. Force


3. Mechanical Equilibrium


4. Equilibrium rule

 

• An object is in a state where there is no change in motion.




1. Inertia


2. Force


3. Mechanical Equilibrium


4. Equilibrium rule




• How fast an object is moving, and in what direction.




1. Speed


2. Velocity


3. Acceleration


4. Free fall




• How fast an object is moving, without consideration of direction.




1. Speed


2. Velocity


3. Acceleration


4. Free fall




• An object is falling under the influence of gravity, and with no air-resistance.




1. Speed


2. Velocity


3. Acceleration


4. Free fall




• The rate at which velocity is changing with time.




1. Speed


2. Velocity


3. Acceleration


4. Free fall

 

Class XI CBSE - Revision Questions MCQ - Semester 1

1. What is the gravitational field strength of a planet when the weight of a 100 kg astronaut is 400 N?

a)      ¼ N kg^-1   b) 9.8 N kg^-1 c) 4 N kg^-1  d) infinity

 

2. The only natural satellite of the earth complete orbits in about

a)      24 days b) 27.3 days c) 30 days d) 365 1/4 days

 

3. The satellite that revolves in a polar orbit is called

a) Natural Satellite b) Geostationary satellite   c) Polar Satellite   d) None of these

 

4)  The height of a communication satellite above the earth’s surface is about

a) 1km b) 100 Km    c) 10,000 Km    D) 36000 Km

 

5) At what depth below the earth’s surface does the weight of  a body  becomes 1% of its value at the surface of the earth?

a) 32Km  b) 64 Km   c) 128 Km   d) 164 Km

 

6) The arte of change of angular momentum is called

a) a Force  b) Torque  c) Impulse  d) None of these

 

7) Which of the following has the largest moment of inertia (Each object has same mass)

a) Solid sphere

b) Bar Magnet

c) Ring about an axis perpendicular to its plane

d) Disc about an axis perpendicular to its plane

 

8) A hollow cylinder and a solid cylinder having same mass and same diameter are related simultaneously from rest from the top of the inclined plane. Which of them will reach the bottom first?

a) Solid cylinder

b) Hollow Cylinder

c) Both will reach the bottom together

d) One having greater density

 

9) A body moving with a constant speed on a horizontal surface does not have

a) Velocity

b) Momentum

c) Kinetic Energy

d) Acceleration

 

10) Which of the following has its unit as Newton-Second

a) Torque b) Momentum   c) Energy   d) Planck is constant

 FIND MORE HERE http://www.scribd.com/doc/7067782/MCQ-on-Basic-Physics

Weightage to Summative Assessement revised by CBSE

The weightage to various assessments will be as detailed below for classes up to IX

FA1 - 10%

FA2 - 10%

SA1 - 30%

FA3-10%

FA 4-10%

SA2 -30%

Thus the two terms have equal weightage for promotion and formative assessment will have 40% weightage and Summative assessment will have 60%  weightage for promotion

Kendriya Vidyalayas of Trivandrum District in Kerala postponed Summative Assessment 1

Kendriya Vidyalayas of Trivandrum District in Kerala postponed Summative Assessment 1 following agitation by activists against Central Government. The class IX and X summative exams have also been postponed. The strike began after the price of petrol increased again. This time the activists targeted Central Government institutions primarily to protest against the central government policies and actions.

It's a common question why the Government of India is not taking positive measures to control the price of Petrol.

Latest News from the Physics World

1. Black holes act as galactic thermostats


2. Physicists in tune with neuronsSun puts relativity to the test


3. Graphene tunes in to terahertz radiation


4. Big science at very low energies

Rotational motion - Flywheel problem

The flywheel has mass m & is rotating with angular velocity w.the radius of the flywheel is R. masses m1 & m2are placed over r1 & r2 radius.find the change in w due to the placing of masses?

Posted by Tushar Srivastava

(Waiting for your responses before posting the final solution)

Motion of connected system - A Numerical problem

A mass 5kg descending vertically,draws up a mass of3kg by means of a light string passing over a pulley.At the end of 4 seconds,the string breaks.How much higher 3 kg mass would go?

Post your solutions as comments to this post

Answer will be posted soon once we get responses from visitors

Difference between Conservative force and Non Conservative force

The basic difference between conservative force and non conservative force is that

• The work done in a closed loop is zero for conservative forces. That is, the work done is independent of path. Gravitational force and electrostatic force are examples. In the case of a non conservative force, the work done in a closed loop is not zero. In other words, for a non conservative force, the work done depends on path followed. Frictional force is an example for non conservative force.

How to Break open a coconut without any weapon?

Have you ever wondered how to break open a coconut nicely if you don't have a tool for it? Watch the video below and it explains how you can do it.

DIRECTION OF TORQUE ACTING ON A CURRENT CARRYING LOOP

HOW TO FIND DIRECTION OF TORQUE ACTING ON A CURRENT CARRYING LOOP PLACED IN A MAGNETIC FIELD ? IS THERE ANY RULE ABOUT IT ?

GAURAV NAGPAL asked

Answer:

 

Proportionality relation in electric power

Power is directly proportional as well as inversely proportional by two formulae.How does one justify?
P=V²/R as well as p=I² R.

 

Answer:

This means that for a given current, (i.e, when current is kept constant) Power is directly proportional to resistance.

eg, when a number of appliances are connected in series, the same current passes though all and the power dissipated  in each will be directly proportional to their resistances.

For a given constant voltage, the power is inversely proportional to resistance.

For eg; when a number of appliances are connected in parallel across the same voltage, then the power dissipated in each is inversely proportional to their resistances.

IITs made their way in World’s top Varsities

QS World university rankings have been declared and IITs have made their way on the list of the World’s top varsities. Cambridge University has topped the list, followed by Harvard University and MIT ranked second and third. Indian Institute of Technology, Delhi was the highest Indian University ranked at 218th followed by IIT Bombay at 225th place.

Sikkim Manipal University joined hands with Edinburgh Napier University

Sikkim Manipal University-Directorate of Distance Education (SMU-DE) has joined hands with Edinburgh Napier University (ENU) on 9th September, 2011. The purpose of this partnership is advancement in teaching, research, academic collaboration, cultural understanding and to create avenues for enhancing student experience.

Degrees given out by IISER Pune and Kolkata are not valid: UGC

Indian Institutes of Science Education and Research (IISER) Pune and Kolkata doled out provisional degrees to the students who passed out from there. However, IISER Pune degrees as well as IISER Kolkata degrees are not valid according to the University Grants Commission (UGC) Act, 1956, which states that only institutions allowed by State or Parliamentary Law or ones having deemed-to-be-university status under Section 3 of the UGC Act can award degrees.

Common Test for PhD in November

Higher education officials at a meeting on 26th August, 2011, decided that common entrance test for PhD will be held in the first week of November. The pattern of the question paper will be decided by the UGC- NET, CSIR, and ICIR. Three cut-off marks will be declared and a score card will be provided to students on the basis of these marks and it will be valid for two years.

Worthy Physics Links

1. http://www.physicsclassroom.com/shwave/
2. http://www.compadre.org/
3. http://www.phys.unsw.edu.au/einsteinlight/
4. http://www.chemeddl.org/resources/ptl/
5. http://www.compadre.org/informal/
6. http://www.compadre.org/precollege/search/browse.cfm?browse=GSSS
7. http://www.compadre.org/psrc/search/search.cfm?gs=228&b=1

The problem of a rock thrown vertically up

A rock is thrown vertically upward from the ground with an initial speed 15m/s.

a. how high does it go
b. how much time is required for the rock to reach its maximum height?
c. what is the rock’s height at t=2.00s?

(Posted by Merhawi)

Answer:

(a)

u=15m/s

a=-10m/s²

v=0 m/s (at the max height)

S=?

v²-u²=2aS

S=v²-u²/2a

=225/20

=11.25 m

(b) From the above case

using v=u+at

t=v-u/a=1.5s

(c) Use S = ut + 1/2 at²

put t=2s, u = 15m/s, a=-10m/s²

S=30 – 20 = 10 m

 

(If you use g = 9.8 m/s² The answers will be slightly different)

How does the size of the bulb in thermometers affect the range and sensitivity of the thermometer?

Do you have an answer? Please feel free to post your answer. We’ll elaborate it after receiving your responses as comments

SUMMATIVE ASSESSMENT 1 FOR CBSE CLASS 9 (GRAVITATION)

Find below a question bank from the chapter GRAVITATION of class 9. Portions up to the syllabus for Summative assessment 1 only is included. The answers are not published herewith. Students are advised to solve the questions and problems and post the questions which they are not able to answer properly or have some doubt with the answer.

Very short answer type questions

1. What is the average value of acceleration due to gravity on earth?
2. What is the value of gravitational constant on (a) earth (b) moon?
3. Does the acceleration of a freely falling body depend on the mass of the body?
4. Name the scientist who gave the three laws of planetary motion.
5. Name the scientist who explained the motion of planets on the basis of gravitational force between the sun & planets.
6. State the Kepler’s III law .
7. Which of the Kepler’s laws of planetary motion led Newton to establish the universal law of gravitation?
8. Name the property of earth which is responsible for extremely small acceleration being produced in it as a result of attraction by other small objects.
9. What is the acceleration produced in a freely falling body of mass 10 kg?
10. Give the formula for the gravitational force between two bodies of masses M1 and M2 kept at a distance d apart.
11. Which force holds the solar system together?

 

(To be continued)

What is Medical Art Press ?

 

If I was searching keywords related to the word medical and found that the following words have got a relatively higher prominence.

medical art press, expat medical insurance, medical air transport, visitor medical insurance, international medical insurance, cigna medical insurance, medical evacuation insurance, overseas medical insurance, holiday medical insurance, global medical insurance, worldwide medical insurance, medical insurance abroad, medical holiday insurance, medical malpractice insurance, emergency medical insurance, temporary medical insurance, medical travel insurance, medical evacuation, travel medical insurance, travel insurance medical, medical travel, private medical cover, student medical insurance, private medical insurance, medical insurance nz, medical intuitive, medical flights, individual medical insurance, buy medical insurance, pet medical insurance, supplemental medical insurance, medical license lookup, affordable medical insurance, cheap medical insurance, personal medical insurance, cheapest medical insurance, medical alert devices, medical scheduling software, medical assistant certification, medical cme, medical insurance coverage, medical insurance quotes, aviva medical insurance, medical coverage, medical practice management, medical id jewelry, medical directive, medical cover, medical transportation services, medical lab coats

Can you write an article on Any or many of these keywords?

  If you get 10000 visits a day for your website or blog and has CTR (Click Through Ratio) of 1% (that is 1 in every 100 visitors click on an advertisement on your website) then you get 100 clicks and you will earn $200 per day if you are signed up with any of the ad networks like adsense, infolinks, affinity, bidvertiser, adbrite etc.

 

If you are constantly posting articles related to such selected keywords, then on an average, you can earn upto $6000 or even more.

Why protons attract inside a nucleus?

What is the reason for proton- proton attraction inside the nucleus according to nuclear physics? (Sanjeev Asked)

Answer: Inside the nucleus where the nucleons are very close to each other, the force which holds them together is the nuclear force, which is the strongest force in nature. The electrostatic force between protons is negligibly small compared to the nuclear force. But the nuclear force is of a very short range, 10^-15 m.

The nuclear force is charge independent, i.e; the nuclear force between proton and proton, proton and neutron as well as neutron and neutron are almost the same.

Yukawa’s meson theory suggest that the nuclear force is an exchange force. The nucleons are bound because of constant exchange of the mesons.

The nuclear force is only felt among hadrons. At small separations between nucleons (less than ~ 0.7 fm between their centers) the force becomes repulsive, which keeps the nucleons at a certain average separation, even if they are of different types. At distances larger than 0.7 femtometer (fm) the force becomes attractive between spin-aligned nucleons, becoming maximal at a center-center distance of about 0.9 fm. Beyond this distance the force drops essentially exponentially, until beyond about 2.0 fm separation, the force drops to negligibly small values.

At short distances (less than 1.7 fm or so), the nuclear force is stronger than the Coulomb force between protons; it thus overcomes the repulsion of protons inside the nucleus.

However, the Coulomb force between protons has a much larger range due to its decay as the inverse square of charge separation, and Coulomb repulsion thus becomes the only significant force between protons when their separation exceeds about 2 to 2.5 fm.

(There are many terms introduced in the explanation. You can discuss them as comments for obtaining further details, if required)

Reference:

1. http://hyperphysics.phy-astr.gsu.edu/hbase/forces/funfor.html
2. http://en.wikipedia.org/wiki/Nuclear_force

Why Rainbow is in the form of an arc?

Why is a rainbow always bent in the shape of a semi circle…?? but according to the theory light travels straight….!!! (Ramesh asked)

What is the difference between centre of gravity,centroid and centre of mass ?

Centroid is the geometric centre of a plane figure or object

Centroid divides the shape into regions of equal moments.

 

 

Centre of mass is the mean location of all masses in a system

 

Centre of gravity is the point through which the weight of a body acts.

 

All these will coincide for a plane figure with uniform density and uniform distribution of mass

Fake Examination Boards Alert

CBSE has published a list of fake Examination Boards

1. All India Board of Secondary Education, Ghazipur, Delhi
2. Board of Adult Education
3. Central Board of Higher Education, Vachaspati Bhavan,Uttam Nagar, New Delhi
4. Board of Adult Education and Training, RS – 295 Brahampuri, Nangal Rai, New Delhi

If you come across any such Boards, you can inform them to the vigilance cell of CBSE or to Police

Where is electricity stored after it is generated but before it is supplied? (Chat Transcript from FaceBook)

Where is electricity stored after it is generated but before it is supplied?

• • 

    Mahesh Sable Electrical power cannot be stored and,therefore,power plants must produce power as and when demanded.power stations r connected in parallel hence load is equally distributed,electric Power can be adjusted with help of step up or step down transformers.

     

  • 

    Mathew Abraham Transformer does not increase power

     

  • 

    Chitraja Rajan The demand for electricity varies randomly within a day itself...so there should be something which should be adjusted according to the demand.

     

  • 

    Vishnu Mohan G huge capacitors? i think i read somewhere like this.

     

  • 

    Rajat Sharma

    Hi All, the question is very smart, i think electricity stored before generation is stored in Water(DAM), Uranium Rods(Nuclear), HydroCarbons(Coal, GAS). Electricity can only store when it is in Direct Current format like in Batteries, Capacitor(its a very small time to store/release) Well there are many source where we can store electricity. When electricity is in demand then Power generation takes place within huge Alternators, this powers generation takes places in terms of Phase Shift between all the power Houses across the country, if this phase shift is disturb then power grid fails. after this the transformers come into picture so as to reduce Resistance loses.

     

  •  

  • 

    Kannan Kannan Ps in my little knowledge electricity unable to store continuing process of generater get current
    >________________________________

     

  • 

    Chitraja Rajan at the generation side electricity is high ac current ..if it is converted into dc then there should be large containers to store them and also need suitable convertors to convert it in either form every time

     

  • 

    Mathew Abraham In modern generators, there are equipment to control the rate of flow of water and in turn rate of rotation as well as the power generated. SO, it is quite right to say that electricity is generated as and when required. When you switch on a device power generation also increases until it reaches maximum capacity. Thereafter we will get less power. Remember the low voltage we suffer during the evening when the power consumption is maximum a few seconds ago · Like

You can also post your questions and answers and participate in discussions online at http://facebook.com/groups/askphysics/

Where is electricity stored after it is generated but before it is supplied? (Chat Transcript from FaceBook)

Where is electricity stored after it is generated but before it is supplied?

• • 

    Mahesh Sable Electrical power cannot be stored and,therefore,power plants must produce power as and when demanded.power stations r connected in parallel hence load is equally distributed,electric Power can be adjusted with help of step up or step down transformers.

     

  • 

    Mathew Abraham Transformer does not increase power

     

  • 

    Chitraja Rajan The demand for electricity varies randomly within a day itself...so there should be something which should be adjusted according to the demand.

     

  • 

    Vishnu Mohan G huge capacitors? i think i read somewhere like this.

     

  • 

    Rajat Sharma

    Hi All, the question is very smart, i think electricity stored before generation is stored in Water(DAM), Uranium Rods(Nuclear), HydroCarbons(Coal, GAS). Electricity can only store when it is in Direct Current format like in Batteries, Capacitor(its a very small time to store/release) Well there are many source where we can store electricity. When electricity is in demand then Power generation takes place within huge Alternators, this powers generation takes places in terms of Phase Shift between all the power Houses across the country, if this phase shift is disturb then power grid fails. after this the transformers come into picture so as to reduce Resistance loses.

     

  •  

  • 

    Kannan Kannan Ps in my little knowledge electricity unable to store continuing process of generater get current
    >________________________________

     

  • 

    Chitraja Rajan at the generation side electricity is high ac current ..if it is converted into dc then there should be large containers to store them and also need suitable convertors to convert it in either form every time

     

  • 

    Mathew Abraham In modern generators, there are equipment to control the rate of flow of water and in turn rate of rotation as well as the power generated. SO, it is quite right to say that electricity is generated as and when required. When you switch on a device power generation also increases until it reaches maximum capacity. Thereafter we will get less power. Remember the low voltage we suffer during the evening when the power consumption is maximum a few seconds ago · Like

You can also post your questions and answers and participate in discussions online at http://facebook.com/groups/askphysics/

Questions waiting to be answered at www.askphysics.com

Can you answer these?

A bullet of mass m is fired with a velocity v and strikes a a block of mass M suspended by a string of length L.
the bullet gets embedded in the block. What is the angle the the block makes due to the impact?

 

Why planets revolve around their own axis?

 

At time t=0 a ball is projected with a velocity = 60 m/s at 60 degrees form x axis.find the times when the velocity will make angle of 45 degree from x axis?

 

Suppose that, while lying on a beach near the equator watching the Sun set over a calm ocean, you start a stopwatch just as the top of the Sun disappears.You then stand, elevating your eyes by a height H = 1.70 metres, and stop the watch when the top of the Sun again disappears, If the elapsed time is t=11.1 s, what is the radius r of earth?

 

A non flow reversible process occurs for which p=3v has power 2+1/v where p is in bar & v is in m has power3. What will be the work done when v changes from 0.5 to 1.5m has power3.

 

Draw  the ray diagram to show the image formation during looming (mirage in cold regions )?

National Cyber Olympiad 2011-12 – Free Sample Papers

Down Load Syllabus For National Cyber Olympiad http://www.sofworld.org/nco/about-nco-exam/nco-exam-syllabus.html

National Cyber Olympiad Sample papers

Having a look at the sample papers is a good practice for preparing for any exam. Download the sample papers and practice them as well as similar problems and questions

Class 2 Sample Papers

Class 3 Sample Papers

Class 4 Sample Papers

Class 5 Sample Papers

Class 6 Sample Papers

Class 7 Sample Papers

Class 8 Sample Papers

Class 9 Sample Papers

Class 10 Sample Papers

Class 11 Sample Papers

Class 12 Sample Papers

Wish you good luck in the exams

National Science Olympiad 2011-12 (NSO)

The National Science Olympiad is conducted by SOF. Science Olympiad Foundation (SOF) is a Registered Not-For-Profit Organization Popularizing Computer, Science, Mathematics and English Education among school children. All activities of the Foundation invariably aim at making learning an interesting and interactive process in which the learner is actually able to put his / her skills, memory, talent and knowledge to test.

SOF offers prizes worth Rs. 4 Crores for the 2011-12 Olympiad exams.

The  prizes for individual winners have become more lucrative as under:

Class 7 to class 12

• 1^st prize –  Rs One lac
• 2^nd prize – Rs Fifty thousand
• 3^rd prize –  Rs Twenty Five thousand
• Rank 4 to Rank 10 –  Rs Five Thousand
• Rank 11 to Rank 20 – Rs TwoThousand Five Hundred
• Rank 21 to Rank 50 – Rs One Thousand
• Rank 51 to Rank 500 – Educational CDs’

Class One to Class 6

• 1^st prize-   Laptop
• 2^nd prize – Laptop
• 3^rd prize – Laptop
• Rank 4 to Rank 10 – Rs Five Thousand
• Rank 11 to Rank 20 – Rs TwoThousand Five Hundred
• Rank 21 to Rank 50 – Rs One Thousand
• Rank 51 to Rank 500 – Educational CDs’

During 2011-12 the first Round of NSO exam will be held on 17^th November, 2011 at participating schools.

Get the syllabus here

Electric field inside a dielectric

Why does the electric field inside a dielectric decrease when it is placed in an external electric field?

(Thushara asked)

Answer:

The net electric field inside a dielectric decreases due to polarization. The external electric field polarizes the dielectric and an electric field is produced due to this polarization. This internal electric field will be opposite to the external electric field and therefore the net electric field inside the dielectric will be less

KERALA PLUS TWO PHYSICS SAMPLE QUESTION PAPER

The following links to SCERT will help you get a handful of good sample papers for preparation for Plustwo Physics Exams including the Onam Examinations

Class X Physics Sample Paper (SSLC) 2006

Sample Question Paper on Electronics

 

Higher Secondary Physics Question Paper