Learn semiconductors and its devices - class XII Physics

EXPECTED QUESTION IN PHYSICS CBSE – BOARD EXAMINATION 2011

EXPECTED QUESTION IN PHYSICS  CBSE – BOARD EXAMINATION 2011

1. State Gauss‘s Theorem. Using the Theorem, derive an expression for the electric field due to a thin infinitely long straight line of charge.

2. State the underlying principle of a transformer. Draw a lebelled diagram of a step down transformer. Mention two sources of energy losses in a transformer.

3. Prove law of refraction by using Huygens principle with neat labeled ray diagram.

4. Derive lens makers formula with neat labeled diagram. Also write the assumptions to be followed.

5. The wavelength λ of a photon and the de-Broglie wavelength of an electron have same value. Show that the energy of the photon is   times the kinetic energy of the electron, where m,c and h have their usual meanings.

(or)

Monochromatic light of frequency 6.0 ×10¹⁴ Hz is produced by a laser. The power emitted is 2.0 ×10^–3 W. (a) what is the energy of a photon in the light beam? (b) How many photons per second, on an average, are emitted by the source?

6. State the basic postulates of Bohr’s theory of atomic spectra. Hence obtain an expression for radius of Bohr’s orbit of a hydrogen atom.

7. Draw the circuit diagram to show the use of a transistor as an oscillator and explain its working.
8. State Ampere’s circuital law and write its mathematical form. Using the law derive an expression for the magnetic field along the axis of an air cored solenoid. Sketch the magnetic lines for a finite solenoid. What is the nature of the magnetic field inside the solenoid?

(or)

     Draw a neat and labeled diagram of a cyclotron. State the underlying principle

     and explain how a positively charged particle gets accelerated in this machine.

     Show mathematically that the cyclotron frequency does not depend upon the

     speed of the particle.

9. Draw a ray of light deviated by a prism. Find the expression for total deviations suffered by the light ray. Draw a graph showing the variation of the angle of deviation with the angle of incidence. Also derive the expression for the refractive index of the material of the prism.

(or)

     (i)Draw a course of rays through a compound microscope. Arrive an

      expression for its magnifying power.                                                                 3M

     (ii)A compound microscope with an objective of focal length f_o = 1.0 cm, and

     an eyepiece with focal length f_e = 2.0 cm, and a tube length of 20 cm.

     Calculate the magnification of the microscope for normal adjustment.

“BEST OF LUCK”

TIPS BEFORE AND AFTER THE CBSE PHYSICS EXAMINATION

BEFORE EXAMINATION

1. Seat and meditate so that you should feel relax.
2. Seat clam . don’t think anything
3. feel free and relax.

AT THE TIME  READING THE QUESTION PAPER

1. Read the questions and mark the direct question you know.
2. Don’t read the application question in the beginning. First complete the all known question by reading it clearly.
3.  Then read the application type question in the area where you read clear and thoroughly.
4. Don’t loose your confident at any moment. This will give the illusion of forgetting nature.

AT THE TIME OF ANSWERING THE QUESTION.

1. Once again read the question stepwise and note down what they are asking. According to the question asked write the answer in stepwise.
2. For one mark questions one should write the reasons even though they are not asked.
3. While writing direct question write as quick as possible. This will help to save time which can be spent for the reasoning type question.
4. While answering for reasoning type question don’t write the answer without writing the formula.
5.  Steps to be followed to do application and problem type questions
1. By understanding the meaning of each sentences write the given.
2. Write the related formula and compare the formulas with the given and the quantity asked to calculate.
3. Apply the conditions and get the result.
6. What ever the type of question may be read the question twice or trice and conform your answer is correct or not
7. Mark the questions that are answered by you in the question paper so that you can have idea of the attempting the questions. This will help you to attempt all questions.  

AFTER COMPLETION OF YOUR EXAMINATION IN THE HALL.

1. Check whether all questions are attempted from question paper by verifying the marking.
2. Check whether the question number is written for all the questions.
3. Check whether the answer written to one mark is OK or not.
4. Check whether the details regarding the pages written are noted properly or not.

AFTER EXAMINATION.

1. Put approximate marks for the questions answered by you.
2. If possible get correct answer and check
3. Satisfy from the mark obtained by you.

“WISHES ALL THE BEST AND BEST OF LUCK”

BY K.SANKAR PGT PHYSICS