FAISALABAD BOARD 2012
PAPER PHYSICS PART-II
Time: 20 Mm
(Objective Part) Marks: 17

Note: Four answer are given against each question in columns A, B, C and D. Select the right answer and on the separate Answer Sheet, fill the circle A,B,C or D with pen or marker in front of that question number.

• The power loss in transformer takes place due to:
  

(a) Eddy current                                             
(b) Magnetic field
(c) Hysteresis                                                 
(d) Eddy current & hysteresis

• The energy density of an inductor is:

(A)  
(b)
(c)                  
(d)  

• In CRO, the output wave form of time base generator is:
  

(a) Circular                                         
(b) Square
(c) Sinusoidal                                     
(d) Saw-toothed

•    of an electron is:
  

(a)                                                
(b)  
(c)                                                 
(d)

• For an open circuit, the current flowing through circuit will be
  

(a) Infinite                                          
(b) Finite        
(c) Maximum                                      
(d) Zero

• What does Nm²C^-1 stand for quantity?
  

(a) Electric field                                 
(b) Electric potential
(c) Electric flux                                  
(d) Electric force

• One of the practical application of electro static induction is:
  

(a) Laser                                             
(b) X-rays machine
(c) Photo copier                                  
(d) Wilson cloud chamber

• The most useful tracer isotope is:
  

(a) Cobalt – 60                                   
(b) Carbo - 14
(c) Iodine - 131                                  
(d) Strontium - 90

• Geiger counter can be used to detect:
  

(a) Charge                                          
(b) Mass
(c)  ratio                                    
(d) Nuclear radiation

• Helium-Neom Laser discharge tub econtains neon:

(a) 82%                                               
(b) 15%          
(c) 25%                                               
(d) 85%

• The uncertainty principle relates uncertainties in the measure meets of energy and:

(a) Velocity                                        
(b) Momentum
(c) Time                                              
(d) Mass of the particle

• Momentum of the moving photon is:
  

(a) Zero                                              
(b) hλ  
(c)                                                     
(d)  

• Pulsating DC can be made smooth by using a circuit known as:

(a) Filter                                             
(b) Tank          
(c) Accepter                                       
(d) All

• Shear modulus is expressed as:

(A) G =                                        
(b) G =
(c) G =                                        
(d) G =

• Conductors have conductivities of the order of:
  

(a) 103(Ωm)^-1                                      
(b) 107(Ωm)^-1 
(c) 107Ωm^-1                                          
(d) 10^-6 Ω

• The power dissipation in AC circuit is expressed as:
  

(a) P = Irms x Vrms Cos2θ                    
(b) P = I x V Cos2θ
(c) P = Irms xVrms Sinθ                        
(d) P = IVSin2θ

• The highest value reached by the voltage or current in one cycle is called:
  

(a) Peak to peak value                        
(b) Peak value
(c) Instantaneous value                      
(d) Root mean square value

Time: 2.40 Hours
(Subjective) 
Marks: 68
SECTION-I

2. Write short answer any Eight Parts.  16

• Suppose that you follow an electric field line due to a positive point charge. Do electric field and the potential increase or decrease? Explain.
• Do electrons tend to go to region of high potential or low potential? Explain.
• Why does capacitance of a capacitor increase when a dielectric material is inserted between its plates?
• Do bends in a wire affect its electrical resistance? Explain.
• What are the difficulties in testing whether filament of a lighted bulb obeys Ohm's law?
• What is conventional current? How does it differ from electronic current?
• A plane conducting loop is located in a uniform magnetic field directed along + x-axis. For what orientation of the loop is the flux
  (a) maximum (b) zero?
• 
  
  Why does the picture on a TV screen is distorted when a magnet is brought near the screen?
  
• Show that the terms E and vB have same units.
  
• What change will be required if we want to convert a DC motor into DC generator?
  
• Why are oscillations of a suspended magnet damped when a metal plate is placed under the magnet?
  
• How does Lenz's law explain law of conservation of energy during phenomenon of electromagnetic induction?

3. Write short ansv is-ny Eight Parts. 16

• Show that ϵ and  have the same units.
•   Find the peak valugf the voltage V0 of an AC supply for which root mean square voltage is 0.7 V0.
• Name the device that will permit flow of direct current but oppose the flow of alternating current and why?
• What is meant by AM and FM?
• Differentiate between amorphous and polymeric solids.
• Define Young's modulus and Shear modulus.
• Distinguish between intrinsic and extrinsic semiconductors?
• What is the effect of forward biasing and reverse biasing on depletion region in a semiconductor diode?
• The inputs of a gate are I and 0. Identify the gate if its output is  (a) 0 (b) 1.
• Why ordinary silicon diodes do not emit light?
• What are the measurements on which two observers in relative motion will always agree upon?
• If you are moving in a spaceship at a very high speed relative to the earth. Would you notice a difference:
  (a) In your pulse rate
  (b) In the pulse rate of people on the earth?

4. Write short answer any Six Parts.   12

•  State the postulates on which special theory of relativity based upon.
• Can an object move with speed of light? Explain.
• Bohr's theory of hydrogen atom is based upon several assumptions. Do any of these assumptions contradict classical physics?
• What is meant by a line spectrum?
• Is energy conserved when an atom emits a photon of light?
• Why are heavy nuclei unstable?         
• A particle which produces more ionization is less penetrating. Why?
• What do we mean by the term critical mass?
• How can radiottaillielp in the treatment of Cancer?

SECTION-II

5(a) electric flux. Calculate the electric flux through a closed surface enclosing a charge "q" at its centre.         04
(b) A platinium wire has resistance of 10Ω at 00c and 20Ω at 2730C. Find the value of temperature co-efficient of resistance of platinium.      04

6.(a)  State and prove the Faraday's law of electromagnetic induction.             04
(b)      How much fast a proton move in a magnetic field of 2.50 x 10-3 T such that the magnetic force is equal to its weight.            04

7.(a) Define impedance and derive a relation for impedance and phase angle for RL and RC series circuit.          04
(b)     A wire 2.5m long and cross sectional area 10-5m2 is stretched 1.5 mm by a force of 100N in the elastic region. Calculate.
(i) The strain                (ii) Young's modulus.          04

8.(a)    Define rectification and describe the working of a half-wave and a full-wave rectifier.    04
(b) X-rays of wave length 22pm are scattered from a carbon target. The scattered radiation being viewed at 850 to the incident beam. What is Compton shift?      04

9. (a)  What is nuclear fusion? Why this reaction has not been brought under control? How sun is issuing out tremendous amount of energy?     04
(b)     Find the wave length of the spectral line corresponding to the transition in hydrogen from n=6 state to n=3 state.  04