## Tribhuvan Univeristy 2074 Bachelor Level four year program 1st year science physics

full marks : 100, Time 3 hrs

Candidates are required to give answers in their own words as far as practicable. The Figures in the margin indicates full marks.

**Attempt all The Questions.**

- What do you mean by the N-coupled oscillator? Describe the all possible modes of oscillations of two particles connected by a spring ? [4+6]

or

Discuss “twisting couple” on a cylindrical rod or write. Find the expression for the work done in a twisting a rod or wire? [5+5]

or

2. What do you mean by canonical ensemble? Describe boltman canonical distribution law ?

or Describe cooling in joule-Thomson expansion. What do you mean by regenerative cooling and casade cooling [4+6]

3. Describe the method of electrical images to find the electrostatic potential and field in the case of a uniformly charged disc. Discuss its application. [8+2]

or What do you mean by decay and rise in time in AC circuit ? Find expression for rise and decay of current in LR and LC circuit ?

4. Distinguish between streamline and turbulent flow of liquid. Find the expression for critical velocity for these types of flow of the fluid.

5. What do you mean by free energy ? Describe Helmholtz’s functions and Gibb’s function. [2+6]

6. Describe the behaviour of plane electromagnetic waves in isotropic dielectric and in conducting media. [ 4+4]

**7.solve any two Questions [2*3=6]**

a) What are the importance of capillaries in series and parallel ?

b) Explain Magnetic vector potential.

c) Describe root mean square speed and most probable speed of particles.

d) What are the results of porous plug experiment ?

**8. Solve all the questions: [ 4*2.5=10]**

a) Explain areal velocity.

b)Why Complex number method for alternating current (AC) analysis is important?

c) Describe the difference between isotropic dielectric media and conducting media.

d) Explain The process of transport of mass through diffusion.

** 9.** A uniform sphere of mass 2 kg and radius 10cm is released from the rest on a inclined plane which makes an angle 30 degree with the horizontal. Find the kinetic energy as it travels 2m along the plane. [5]

10. If window blows 40m/s over house , What will be net force on the roof if it has surface area 250cm^2? (Density of air = 1.29kg/m^3)

11. A spherical Satellite orbiting Earth is lighted on one side by the sun, with intensity 1340 w/m2. If the Radius of satellite is 1.00m, What power is incidient upon it ? [ Note : The Satellite effectively intercepts radiation only over a cross section- an area equal to the if a disk , Pie r^2 ] Calculate the peak electric and peak magnetic Field. [5]

12. Two identical coils carrying equal currents have a common center and their planes are right angles to each other. What is the ratio of its magnitude of the resultant magnetic field and the field due to one coil alone at the center ?

13. How much work must be done to exact 10.0j of heat (a) from a reservoir at 7 degree celcios and transfer it to one at 27 degree celcious by means of a refregerator using a Carnot cycle (b) From one at -73 Degree to one at 27degree From one at -173 degree to one at 223 degree to one at 27 degree?

14. The filament of a light bulb is cylindrical with length l = 15mm and radius r= 0.04mm. The filament is maintained at a temperature T=6000k by an electric current. The Filament behaves approximately as a black body, emitting radiation isotropically. At night, you observe the light bulb from a distance D=5km with pupil of your eye fully dilated to a radius density=3mm (a) How much Radiation power enters every second ? [ you can assume that the average wavelength for the radiations is = 600nm] [5]

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