Phys 114-internal 2004

Universal Science College Internal Examination Subject: Phy 114 (Physics) Date: Feb 8, 2005

(B. Sc. Biochemistry) First Semester 2005

Full Marks: 100 Pass Marks: 45 Time: 3 hours

Candidates are required to give their answers in their own words as far as practicable. The figure in the margin indicates the full marks. Group A Long Questions (Any three ) (3× ×14 = 42) 1. What does mean the electrical resonance? Obtain an expression for the net impedance in LCR- parallel circuit. What does mean the tuned in parallel circuit? What are the advantages of tuned circuit in electronics? Or What is an oscillator? With a neat diagram, discuss the circuit operation of tuned collector oscillator what is the nature of oscillations produced by tank circuit? How will you get undamped oscillations from a tank circuit? What are the advantages of oscillator? 2. What are the liquid crystals? What do you mean by "Freedericksz transition"? What are the magnetic and electric effects on liquid crystals? Describe in detail the "Smetic phase" of liquid crystal. 3. Define term "excess pressure". Find the expression for excess pressure and also find the expression for rise of liquid inside capillary tube on the basis of excess pressure with net diagram. 4. Find the expression for the measurement of distance of planet using: (a) Parallax method (b) Copernicus method and (c) Keplar third law method Group - B Short Questions: (Any six) (6× ×7 = 42) 1. With a single experiment how can you show that light waves are transverse in nature and the phenomenon of polarization? In place of polarizer if a crystal of liquid is placed what will happen? 2. A constant voltage a.c. generator of 20 V r.m.s. and variable frequency is connected in series with a resistor of resistance 2.0Ω, a coil of inductance 5.0 H and a capacitor of capacitance 2.0 µF. The frequency is adjusted until the current in the circuit has a maximum value of 2.0 A r.m.s. Calculate the resistance of the wire of the inductor and the value of this frequency. (Assume G2 = 10) 3. In the circuit shown below if Vcc = 10 V and Rc = draw the d.c. load line. Where will be the Q – point if zero signal base current is 20 µA and B = 40?

IC

No signel

VBB 4. 5. 6. 7. 8.

RC = 4 kΩ, VCC = 10 V

Explain the working of full wave bridge rectifier with a neat sketch and derive an expression for the efficiency of a full-wave rectifier. Explain about death of star under consideration of solar masses. Define related terms for Milky Way galaxy. Explain shape of liquid meniscus on the bass of angle of contact. If the radious of the sun is 6.95 x 108 m and its distance from earth is 1 AU, calculate the surface temperature of sun. (Given Stefan constant = 5.735 x 10-8 W m -2 K-4 and solar constant = 1.39 x 103 W m-2.)

Group – C Write short notes on: (Any eight) 1. What do you mean by displacement current? Give the physical concept. 2. What are the advantages of amplifier in electronic circuit? 3. Define the term "Hysterisis". What are the advantages of hysterics loop? 4. What do you mean by plane polarization of light wave? Explain in short. 5. What parameter determines the liquid crystalline structure? Analyse mathematically in short. 6. Describe the Nematic phase of liquid crystal in short. 7. Define redshift 8. Calculate IE in a transistor for which β = 50 and IB = 30 µA. 9. Define meteors and meteoroids 10. Why hot soup taste better than cold one? 11. Define surfaitants 12. Why detergent is used to clean clothes? ***

(2× ×8 = 16)