CSIR-NET and GATE physics: de Brogli wavelength

CSIR-NET and GATE physics: de Brogli wavelength: "Interference, diffraction and polarization establishes the wave nature of light and can be explained on the basis of wave theory photoelectr..."

Sample questions for AISSCE board exams

Try to solve these questions on your own in my net post I'll publish 3 marks and 5 marks sample questions.
Question 1. W cm apart on a hat is the amount of work done in moving 100 nC charge between two points 5 cm apart on an equipotential surface?                                           1
Question 2. What is the value of refractive index of medium of polarising angle 60 degree?                                1
Question 3. State two factors on which temperature of inversion of a thermocouple may depend.                              1
Question 4. In which direction would a compass needle align if taken to geographic (i) north and (ii) south pole?                                     1
Question 5. The instantaneous voltage from an a.c. source is given by E=300 sin 314t . What is the r.m.s. voltage of the source?                                             1
Question 6. Compare the radii of two nuclei with mass number 1 and 27 respectively.                                           1
Question 7. How does energy gap in an intrinsic semiconductor vary, when doped with a pentavalent impurity.                                                      1
Question 8. If the temperature of good conductor increases, how does the relaxation time of electrons in the conductor change.                          1
Question 9. Draw a labelled ray digram shwing the formation of image using a Newtonian type reflecting telescope.                                           2
Question 10. The output voltage of an ideal transformer, connected to a 240 V a.c. is 24 V. When transformer is used to light a bulb with rating 24 V , 24 W, calculate the current in the primary coil of the circuit.                                                     2
Question 11. Can magnetic field set a resting electron into motion.                                 2
Question 12. You are given two niclei 3X7 and 3Y4. Are they isotopes of same element? State the resion . Which one of the two nuclei is likely to be more stable.                                                              2
Question 13. A heater coil is rated 100 W , 200 V. It is cut into two identical parts. Both parts are connected togather in parallel , to the same source of 200 V. Calculate the energy librated per second in new combination.                                                          2
Question 14. A charge q moving in a straight line is accelerated by potential difference V. It enters uniform magnetic field B perpandicular to its path . Deduce in terms of V an expression for the radius of circular path in which it travels.                                2
Question 15. State the reason for the following observations recorded from the surface of the moon:
(i) sky appears dark
(ii) rainbow is never formed.
Question 16. Write any three characterstics , a ferromagnetic substance should posess , if it is to be used to make a permanent magnet. Give one example of such material.                      2
Question 17. The value of ground state of hydrogen atom is -13.6 eV.
(i) What does the negative sign signify.
(ii) how much energy is required to take an electron in this atom from ground state to the first exited state.                2

Questions and answers for AISSCE board exams

Question 1.  Why electron capture is common in case of heavy nucleus?
Answer. A heavy nucleus has large positive charge. Moreover, the raidus of K-shell in heavy nuclei is much smaller than that in case of light nucleus. Due to both these factors, the K-shell electrons experiences a large force of attraction due to positive nucleus and is keptured by it.

Question 2. Why is nuclear fusion difficult to carry out?
Answer. The fusion reaction require very high temperature condition and it has to be obtained by causing explosion due to fission process. Further , due to very high temperature no material can sustain the region where fusion is to be carried out.

Question 3. Would you prefer to use a transistor in CB or CE as a amplifier?
Answer. Transistor in CE configuration as an amplifier as curent gain in this case is more than that as in case of amplifier in CB configuration.

Question 4. Explain why the core of the transformer is laminated?
Answer. The core of a transformer is laminated so as to reduce loss of energy due to eddy currents. The magnitude of the eddy currents set up is considerably minimised, when the core is laminated.

Question 5. Why is the core of a transformer made of a magnetic material of high permeability?
Answer. The transformer works on the principle of mutual induction. In case, the core has a high value of magnetic permeability, the magnetic field lines will crowd through the core and the magnetic flux linkage between the two coils will also be large.

Question 6. When the motor of an electric refrigerator starts, the lights in the house become dim momentarily. Why?
Answer. When the electric motor of the refrigerator starts, it draws maximum current from the a.c. mains. It is because, just at the start of the motor, the back e.m.f. is zero. Due to the large current drawn by the motor, the current through the lights (connected in parallel) decreases and they become dim. However, as the armature of the motor rotates, back e.m.f. is produced and the motor draws current less than that drawn in the beginning . Then, the lights recover their brilliance.

Manage yourself for competetions (think about these thoughts)

1. First of all have a positive attitude it pays and whatever you are thinking of doing do it now i mean start doing whatever you are planning to do or have planned to do so far.


2. Try and manage your stress levels , if stressed most easy part of your syllabus would seem hard and difficult to learn. So maintain your cool.

3. Do not panic if you failed once think about your mistakes, identify your weak link and start preparing again with only success in your mind. Remember that failure means delay not the defeat.

4. Never let yourself be stopped by the loss of one opportunity , think , discover another one and start working for it.

5. Organise yourself so that you can make best out of your limited time.

7. Last but not the least try being fair and genuine with your competitors.

Manage yourself for competetions (think about these thoughts)

1. First of all have a positive attitude it pays and whatever you are thinking of doing do it now i mean start doing whatever you are planning to do or have planned to do so far.
2. Try and manage your stress levels , if stressed most easy part of your syllabus would seem hard and difficult to learn. So maintain your cool.
3. Do not panic if you failed once think about your mistakes, identify your weak link and start preparing again with only success in your mind. Remember that failure means delay not the defeat.
4. Never let yourself be stopped by the loss of one opportunity , think , discover another one and start working for it.
5. Organise yourself so that you can make best out of your limited time.
7. Last but not the least try being fair and genuine with your competitors.

IITJEE previous year questions

Question 1
A particle executes SHM with frequency f. The frequency with which its Kinetic energy oscillates is
(a) f/2
(b) f
(c) 2f
(d) 4f

Question 2
A linear harmonic oscillator of force constant 2 x 106N/m and amplitude 0.01 m has a total mechanical energy of 160J. Its
(a) Maximum potential energy is 100J
(b) Maximum kinetic energy is 100J
(c) Maximum potential energy is 160J
(d) Minimum potential energy is zero

Question 3
A given quantity of ideal gas is at pressure P and absolute temperature T. The isothermal bulk modulus of gas is
(a) 2P/3
(b) P
(c) 3P/2
(d) 2P

Question 4
During the melting of slab of ice at 273K at atmospheric pressure
(a) positive work is done by the ice water system on the atmosphere
(b) positive work is done on the ice water system by the atmosphere
(c) the internal energy of the ice water system increases
(d) the internal energy of the ice water system decreases


Question 5
When an ideal diatomic gas is heated at a constant pressure , the fraction of the heat energy supplied which increases the internal energy of the gas is
(a) 2/5
(b) 3/5
(c) 3/7
(d) 5/7
 
Question 6
In a given process on an ideal gas , dW=0 and dQ<0. then for the gas
(a) the temperature will decrease
(b) the volume will increase
(c) the pressure will remain constant
(d) the temperature will increase

Question 7
A cylinder rolls up an inclined plane, reaches some hight, and then rolls down (without slipping through these motions). The directions of frictional force acting on the cylinder are
(a) up the incline while ascending and down the incline descending
(b) up the incline while ascending as well as descending
(c) down the incline while ascending and up the incline while descending
(d) down the incline while ascending as well as descending
 
 

Answer
1. c
2. c,d
3. b
4. b,c
5. d
6. a
7. b

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