Physics homework XII-25th Feb Sunday

1. What is doppler effect? Find an expression for the change in apparent frequency when the source passes by the stationary observer.
2. Whistle of an approaching train is shriller. Why?
3. A tunning fork has two prongs. Why?
4. In which medium is the angle of polarization greater, rarer or denser?
5. Define a.c.power. Derive an expression for it. Also define power factor.
6. What is wattless current?
7. What do you mean by radiation hazard? What are its safety measures?
8. Give a brief account on "Energy sources of Nepal".
9. Explain the term artificial radio isotopes.
10. What do you mean by dark energy and dark matter?

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Physics homework XI-23rd Feb Friday

1. Derive an expression for the energy stored in a charged capacitor and also find energy density.
2. Obtain expressions for the equivalent capacitance when the capacitors are connected in series and parallel combination separately.
3. What are polar and nonpolar dielectic?
4. What is surface tension? Derive an expression for it using capillary rise method.
5. Explain why the liquid drops are spherical in shape?
6. Hot soup are tastier than cold one. Why?
7. Why has a gas two values of molar heat capacities?
8. What is adiabatic process? Derive an expression for the workdone in this process.
9. What is angular magnification? Obtain it for compound microscope when final image is formed at near point.
10. What is f-number of camera?

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Physics homework XII-18thFeb 2018-Sunday

1. What is Doppler's effect? Obtain an expression for the change in apparent frequency when an observer passes by a stationary source.
2. State the laws of radioactivity and derive decay equation.
3. What is green house effect?Discuss its effects, sources and the controlling measures.
4. Discuss the phase relationship between the voltage and current in a.c. circuit containing capacitor and resistor in series and hence derive an expression for the impedance of the circuit.
5. Why is a choke coil better than a resistor in an electrical appliances?
6. What is meant by impedance of an a.c. circuit?
7. What do you mean by curie?
8. What is acid rain? Explain.
9. What is global warming? Explain.
10. What are ultrasonic and infrasonic?
11. Which has a more direct influence on the loudness of a sound wave: the displacement amplitude or the pressure amplitude? Explain.
12. Bats catch their prey in the dark even when they don't see the prey. How can this happen?
13. A tuning fork has two prongs. why?
14. State Hubble's law and write the significance of Hubble's constant.
15. What are quarks? Write their names with charge they contained.

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Physics homework XI-16th feb 2018-friday

1.       What is the magnitude of an electric field, which will balance the weight of an electron on the             surface of earth?
2.       A parallel plate air capacitor of capacitance 2.45 pF has a charge of magnitude o.148 �C on each         plate. Find the potential difference and electric field intensity between the plates if the distance           between the plates is 5mm?
3.       Obtain the value of g from the motion of moon assuming that its period of rotation round the               earth is 27 days 8 hours and the radius of its orbit is 60.1 times the radius of the earth. Radius of         earth = 6.36�10⁶ m.
4.       A simple pendulum 4 m long swings with an amplitude of 0.2 m. compute the velocity of the               pendulum at its lowest point and its acceleration at the extreme ends.
5.       Angle of contact of mercury with glass is 135�. A narrow tube of glass having diameter 2mm is           dipped in a beaker containing mercury. By what height does the mercury go down in the tube               relative to the level of mercury outside? Surface tension of mercury = 0.547 Nm^-1 , Density of             mercury = 13600 kgm^-3
6.       The correct inflation of a tyre at 20� C is 2 kg/cm². After driving several hours, the driver checks        the tryes. If the tyre�s temperature is 50�C, what should be the pressure reading?
7.       If  earth shrinks, how will be the duration of a day affected?
8.       A body floats in a liquid contained in a beaker. The whole system falls under gravity. What is            the value of upthrust on the body due to liquid?
9.       A student claimed that thermometers are useless because a thermometer always registers its own         temperature. How would you respond?
10.   Why do we feel uncomfortable during very high relative humidity of air?
11.   Why does a refrigerator consume more power in summer than in winter to cool the same                     quantity  of food by same degree?

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Physics homework XII-11th February Sunday

1. What are beats? Derive an expression for beat frequency.
2. How is it that one can recognize a friend from his voice without seeing him?
3. What is polarization of light? State and prove Brewster's law.
4. Is polarization possible for longitudinal wave?
5. What is meant by wattless current?
6. What are advantages of a.c over d.c.?
7. Derive the condition for resonant frequency of LCR alternating current circuit.
8. What is noise pollution? Mention its sources and preventions.

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Physics homework XI-9th February Friday

1. Define capacitance. Derive the capacitance of a parallel plate capacitor.
2. Explain how the capacitance of a parallel plate capacitor can be increased.
3. What are the uses of dielectric in a capacitor?
4. What is angular magnification? Derive an expression for it for astronomical telescope in normal adjustment and when final image is formed at near point.
5. Why mercury does not wet the glass tube?
6. The tip of the nib of a pen is split. Why?
7. Define surface tension and surface energy of a liquid and derive a relation between them.

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Physics homework grade XII-for 4th Feb Sunday

1. What is pressure amplitude? Obtain an expression for it.
2. Define Intensity of sound. Obtain an expression for it.
3. If the pressure amplitude of a sound wave is halved, by what factor does the intensity of the wave change?
4. What is meant by threshold of hearing?
5. Why is the roaring of lion different than the sound of a mosquito?
6. How is it that one can recognize a friend from his voice without seeing him?
7. A nucleus contains no electrons, yet it ejects them. Explain.
8. How do the mass number and atomic number of a radioactive element change in an alpha, beta and gamma decay?
9. How do beta particles differ from electrons?
10. Discuss the importance of physics for the development of nation.
11. A transformer gets heated up while in use. Why?
12. Find the impedance of LCR circuit in series.

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Physics homework grade XI-2nd Feb Friday

1. What is capacitance? Derive an expression for the capacitance of a parallel plate capacitor?
2. Why are bridges declared unsafe after a long use?
3. Explain which one is more elastic, rubber or steel?
4. Define different types of stress and strain.
5. What is surface tension? Establish a relationship between surface tension and surface energy.
6. State first law of thermodynamics.
7. Prove that Cp -Cv =R
8. What are Myopia and Hypermetropia? How are they corrected?

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