CBSE Physics

Why revise regularly?

It has become a practice among many students (compared to a few decades back) to read only what is taught the day and not what happened before.   Though it is a good practice to start with current topic, revising back to the beginning as much as possible is very much helpful in performing well in exams. Every time you repeat, the mind seeks new meanings and interpretations and this becomes helpful while answering the HOTS questions (If you have the determination to answer every question to the best of your ability & beyond!) When we read again and again new questions related to the topic arises in our mind and the effort to answer the questions is the beginning of true learning. Only when you read with an active, curious and questioning mind, learning becomes effective. And don’t rest until you find satisfying and convincing answers to your questions… The answers, the explanations and the logical reasoning developed by you will last forever. But always discuss those with a good teacher. Sometimes it happens that the explanations developed by oneself has some faulty considerations and may be violating the basic principles of conservation or some other of the sort.

I don’t want to Pass Exam ! No one said ever …


pass examEveryone wants to pass exam – especially when it comes to Board Exams. Many enjoyed the entire year in company with friends from the class and outside. Now the exam fever is on and some are finding it difficult to get pass marks and Physics is the one subject many find it difficult to mug up in a hurry. So, here we have come up with a sure shot method to succeed. If you are ready to work hard, you can score more than 50% marks with the method we suggest. But you should strictly follow the schedule.


Step #1

Make a strong determination and say aloud “I will Pass Exam”

Your decision and determination will work more than anyone else’s. The first step towards to success is to believe that you can do it and be ready to work for it irrespective of the hardships and troubles you may face during the course. Put a reminder at a visible place so that you’re always reminded of your decision to pass exam. Go to next page

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CBSE Physics– important diagrams electromagnetic induction and AC


CBSE Physics Class XII Important diagrams from Electromagnetic Induction and AC can be downloaded here.

The students should note that the diagrams are to be as per the text books and therefore we have taken care to follow the text book in preparing the files.

The following diagrams are included in the file


  • teacher in class.jpg Faraday’s Experiment on Electro Magnetic Induction
  • Illustration of Lenz’s law
  • Motional emf
  • Eddy current
  • Mutual inductance of two solenoids
  • AC generator



  • AC circuit with R only
  • AC circuit with L only
  • AC circuit with C only
  • LCR AC series circuit
  • Impedence diagram
  • LC oscillations
  • Resonance in LCR series circuit
  • Transformer


ELECTROMAGNETIC INDUCTION  — Important diagrams from emi

ALTERNATING CURRENT — important diagrams from ac


Learn the principles to score better in Physics practicals and viva


Hello! Dear students,
CBSE Practical Exams started on 16th and will be completed by15 Feb. Do you know that Practical marks play an important part in giving you a decent percentage? In this competitive world each and every mark is important and will decide you future. So try your best to score the maximum in practical exam. It’s not very difficult to score 30/30 a perfect 100%. Follow these guidelines and you can,


Teacher talking to student at LSI

Every student is expected to record 15 experiments. 8 from section A and 7 from section B. All these must be done and signed by the teacher in charge. There must be a properly maintained index signed by teacher. The certification is a  must. Your teacher and school Principal should certify that the record book is bonafide with the seal of the school.

Activities are also to be recorded.
Investigatory Project
Every student should also submit a record the investigatory project done during the year. This may be submitted in a file. The report may be handwritten or typed. All the sections of the project like introduction, motivation, principle, hypothesis.etc Bibliography is an essential component of the project work. The project report should also contain a “bonafide’ certificate. As part of the project, there should be some data analysis, graph etc and a conclusion.
Viva Voce


The performance in Viva Voce is very important. This is your chance to impress the examiner. For this you need to prepare well. Practice all circuit diagrams and ray diagrams. The principle behind a involved in each experiment is a sure shot.
All the best! Please feel free to ask in case of any doubt. Use the comment column.

How to get pass marks in Physics in days?


Some students asked me this. These were students who never passed in any of the Physics tests during the year when they were in class 12.


Now that the exams are near, they are eager to pass with least effort.


I consoled them, and said, “If you believe and promise to do what I say, you can get more than pass marks in just  days effort.”


They agreed.


The formula I gave them and which fetched them good marks is listed below.


English: Two students studying English at a Ta...


  1. There are some derivations and constructions which are commonly asked in exams. With the help of your teacher identify the portions and learn them well. Take atleast fifteen such portions. Write and practice. Remember, these five days can change your future for ever.
  2. Write all formulae with explanation of each term in a paper. Use them to solve atleast five numericals from each chapter.
  3. Write all laws and principles and learn them by heart.  Try to write from memory and make sure that you can do it without any mistake.
  4. Practice all diagrams
  5. Revise whatever you learnt


Here you go! Do the above with confidence. Practice well, avoid distractions. Eat healthy food. Pray and practice. YOU WILL WIN




How was your AISSCE CBSE Class 12 Physics Exam 2013?



How was the CBSE Class 12 Physics Exam today?


Central Board of Secondary Education


Was it easy or difficult?

Many students reported that the questions were unexpected and extra ordinarily tough. What was your experience?


Were there questions beyond your comprehension?


Were there questions out of Syllabus?


Post your responses Now!

Anju R  writes:

The Physics CBSE exam was tough.It was not beyond the syllabus but it was confusing and was asked in a twisted manner.Almost all the students who prepared for the exams didnot leave any derivations,laws etc.But the saddest part was that they asked the big derivation for just one mark and only very few were asked.And most questions were unexpected ones.
It was painful when I saw that after the exam almost all the students were crying.Sitting for a whole night for studying the derivations,laws etc.. gave nothing to us other than tears.We were happy after the English exam but the Physics exam gave a terror over us about Board Exams.I think 90 %  of the students could not complete saying that it was a lengthy paper.

The preliminary examination of the All India P...

During the exam I could see many sitting with great confusion while few others in a hurry to complete  it and the rest of them sitting sadly.By the grace of God I completed 5 minutes before the alloted time and didn’t leave any question.I hope CBSE will consider us.

Yours sincerely,






Faster than Light!


Mathew Abraham (A Physics Teacher in KVS) claims (on FaceBook) that faster than light communication and transfer of matter is possible and the fact will be revealed in near future.

See the transcript below.


I believe and maintain that “faster than light communication and transfer of matter is possible”. We have to find how?

  • Vishnu V Mohan Maybe communication.But wat abt matter?
  • Mathew Abraham It’s somewhat like a revelation to me, I hope that particles travelling faster than light would soon be discovered and that discovery would lead to interstellar travel in near future

    What do you think?


Physics Musings on Beer


Do you know there are a lot of Physics facts hidden behind a glass of beer.




Institute of Physics (UK) has launched a Christmas website based on beer, to help explain some of the more peculiar scientific phenomena hidden in a glass of beer.


The site explains many facts of Physics too based on the beer story.


It says that the bubbles are not rising but they are constantly falling in a g;ass of beer. Can’t believe? Visit the site to know more.



Class 12 physics question bank


Download an excellent collection of questions with answers for CBSE Class 12 Physics

Question Bank in Physics Class XII

The collection will also be helpful for students of other syllabuses.

Central Board of Secondary Education

The file consists of syllabus, key points, collection of very short Answer (1 mark), Short answer type question – solved (2 marks), short answers (3 marks), Long answers (5 marks), Solved numericals and 3 sample papers.

The contents are arranged chapter-wise. Any student will find this a boon for easy preparation and to score better marks in Physics.

Relatively relative


Most of you might know einstein as being synonymous with genius. Yes he is the epitome of creative science and is still regarded as idols by some of the finest scientists of the world. Even the top most scientists considered him as being a revolutionary as his out of the box thinking. Today we are going to touch upon his theory of special relativity.

Right so first we shall discuss a bit about relative speeds.
Let us suppose that there be a system of two bodies named a and b respectively which were moving with velocities va and vb respectively towards the left. Now if you were standing on the ground at rest you would notice that both moved towards the left with velocity va and vb respectively. However if you were on the object a you would notice that the velocity of b looks to you like va-vb towards you(towards a) (here we are considering that va>vb)however if you were on b you would notice that b is moving towards you with velocity vb-va. Now if one of the objects were to be accelerated and supposing you were on the accelerating body you would feel as if a pseudo force was acting upon you which caused you (the object ) to move towards the other object with a greater speed. Hence to find out the real force acting upon you you would need to have an observer in the inertial frame of reference. However where is this frame of reference?
If you think about it you yourself are not in an inertial frame of reference  are you?
You are rotating on the earth and a rotating body is certainly not an inertial frame of reference as there is a pseudo force acting here as well called the centrifugal force.
So is there any point in the universe which can be called an inertial frame of reference? Scientists began looking for this stationary frame of reference and they were fixed upon ether. Ether was supposed to be a hypothetical jelly like fluid medium through which light propagates. However the michelson-morley experiment disproved the existence of ether. Hence scientists were now worried as without any fixed frame of reference they could not work out the electromagnetic theory as proposed by Maxwell for maxwell’s theory of electromagnetic waves were absolutely perfect in their description.
Now this is where einstein comes into the picture. He had been continuously thinking of how to make the electromagnetic theory work without the need of an inertial frame of reference. And then while looking at a big clock tower he finally found his eureka moment. He had been thinking if the speed of light was the same in all inertial frames and didn’t know how to make that work. That’s when it hit him that maybe time was affected in the overall process. And then he postulated his special theory of relativity.
The two postulates of his special theory of relativity are:
1) the laws of physics are the same in all inertial frames of reference.
2) the speed of light is constant in all frames of reference.
These two postulates worked perfectly as it has been measured to be found that the speed of light was truly constant in all inertial frames of reference.
Here is what this means. In our previous example we used the objects a and b. Now let us suppose that a shone a torch light towards b. Let the speed of light to an inertial frame of reference be c. Then the light beam is supposed to have reached b at a speed of c-(va-vb).
However it will be found that the speed with which the light beam still reached b is still c.
It discarded the need of an absolute inertial frame of reference and hence the notion of ether.

However it had certain consequences as well like time dilation and space contraction!
What are they?
Well here is a brief example of what it might look like.
Supposing there was an observer in the S frame which is relatively at rest to another frame and suppose there was another frame S’ which moved with a velocity v with reference to the stationary frame S.
Velocities (and speeds) do not simply add. If the observer in S measures an object moving along the x axis at velocity u, then the observer in the S′ system, a frame of reference moving at velocity v in the x direction with respect to S, will measure the object moving with velocity u’ where (from the Lorentz transformations above):
The other frame S will measure:
Notice that if the object were moving at the speed of light in the S system (i.e. u = c), then it would also be moving at the speed of light in the S′ system. Also, if both u and v are small with respect to the speed of light, we will recover the intuitive Galilean transformation of velocities


While the equations do look big and scary i will try to make it look fascinating instead. If you look at the equations a bit more carefully you will see that at speeds close to the speed of light.
From these equations you will find that even the speeds of both the frame and the object cannot exceed the speed of light.
C+C is not equal to 2C!!

Also here are some more scary equations…Bear with me!
Consider two observers O and O’ , each using their own Cartesian coordinate system to measure space and time intervals. O uses (t, x, y, z) and O ‘ uses (t’ , x’ , y’ , z’ ). Assume further that the coordinate systems are oriented so that, in 3 dimensions, the x-axis and the x’ -axis are collinear, the y-axis is parallel to the y’ -axis, and the z-axis parallel to the z’ -axis. The relative velocity between the two observers is v along the common x-axis. Also assume that the origins of both coordinate systems are the same, that is, coincident times and positions. Then?

  • v is the relative velocity between frames in the x-direction,
  • c is the speed of light, is the Lorentz factor,  again for the x-direction.


Here is what these equations tell you. They tell you that if you were moving towards an object which is stationary with reference to a stationary frame of reference with a speed close to that of the speed of light, the moving object would find  takes greater time  to travel a certain distance than if it were measured by an observer on the fixed reference frame. Meaning?
Time slowed down for the fast moving object.
Also in the frame of reference of the moving object itself. It would find that the moving object had to travel a lesser distance than what it would have to travel as measured from the frame of reference of the stationary observer.

I have not explained the works to my readers as it would go on for pages. However I hope you understood how relativity opens up the doors to slowing down time or contracting space! Einstein wasn’t a genius for nothing! He literally opened up the door for turning something as fictional as star wars into a living reality!!

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