RAWALPINDI BOARD 2014
PHYSICS
PART-II
Time: 20 Min.
(Objective Part)
Marks: 17
Note: You have four choice for each objective type question a A,B,C and D. The choice which you think is correct; fill that circle in front of that question number. Use marker or pen to fill the circles. Cutting or filling two or more circles will result in zero mark in that question.

• Laser is beam of light which is:

(a) Monochromatic
(b) Coherent
(c) Unidirectional                    
(d) All these

• Speed of the electron in the first Bohr's orbit is:

(a) 2.19 x 1O⁶m / s  
(b) 2.19 x 10^-6m / s
(c) 2.19 x 10⁶ cm /s  
(d) 2.19 x 1O^-6 cm / s

•  The particles equal in mass but greater than proton are:

(a) Mesons
(b) Baryons
(c) Leptons
(d) Hadrons

• At higher energies more than 1.02 Mev the dominant process is:

(a) Photo electric effect       
(b) Compton effect
(c) Pair production  
(d) Nuclear fission

• When a dielectric is placed between two charges, then coulomb's force will be:

(a) Increased            
(b) Decreased
(c) Zero       
(d) Negative

• A capaciro stores energy in the form of:

(a) Magnetic field   
(b) Heat energy
(c) Electrical energy
(d) Mechanical energy

• Charge carriers in electrolytes are:

(a) Protons
(b) Electrons
(c) Holes     
(d) Positive and Negative Ions

• Brightness in cathode ray oscilloscope is controlled by:

(a) Grid        
(b) Filament
(c) Anode   
(d) Cathode

• The Lenz's law is in accordance with law of conservation of

(a) Mass      
(b) Energy
(c) Charge  
(d) Momentum

For step down transformer:

(a) Ns > NP 
(b) Np > Ns
(c) Ns = Np 
(d) Ns >>> Np

• Energy density in an inductor is:

Directly proportional to magnetic field.
Directly proportional to square of magnetic field.
Inversely proportional to magnetic field,
Inversely proportional to square of field.               

• Root mean square value of voltate is given by:

(a) Vrms =2V₂
(b) Vrms = ₂
(c) Vrms = V₂
(d) Vrms =Vo

• Inductive reactance of an inductor is:

XL = πƒL    
XL = 4πƒL
XL = 2πƒL
XL = 2πL

• There are different crystal systems. The number of these crystal systems is:

(a) 3      
(b) 4
(c) 5
(d) 7

• The potential barrier for silicon is:

(a) 0.3 V 
(b) 0.5 V
(c) 0.8 V
(d) 0.7 V

• Pulsating output of full wave rectifier can he made smooth by using circuit called:

(a) Filter              
(b) Amplifier
(c) Resistor        
(d) Transistor

• If an object moves with speed of light, its mass will be:

(a) Zero               
(b) Maximum
(c) infinity           
(d) Minimum

RAWALPINDI BOARD 2014
PHYSICS
PART-II
Time: 3:10 Hour
(Subjective Part)
Marks: 83
Section-II

• Show that ε and  have same units.
• Electric lines of force never cross. Why?
• Write a note on back motor effect in generator.
• Define magnetic flux its units.
• Show that Ohm times Farad is equal to second. What is polarization and how dipoles are formed in dielectric?
  
• Electromagnetic induction is exactly in accordance with the law of conservation of energy. How?
  
• Why  is zero inside a charged rubber balloon? When charge is distributed uniformly over its surface?
• When an electric motor, such as an electric drill is being used, does it also act as a generator? If so what is the consequence of this?
• Is it possible to orient a current loop in a uniform magnetic field such that the loop will not lend to rotate? Explain.
• Why a voltmeter should have very high resistance?
• Suppose that a charge “q” is moving in a uniform magnetic field with a velocity V. Why is there no    work done by the magnetic force that acts on the charge q?
  
• Electromagnetic induction is exactly in accordance with the law of conservation of energy. How?

3. Attempt any EIGHT short questions. (8 x 2 = 16)

• Why does resistance of a conductor rise with to
• State Kirchhoff’s rules.
  
• Write down advantages and disadvantages of A.M and F.M.
  
• Distinguish between brittle and ductile substances.
  
• What do you mean by high temperature super conductor?
  
• Define unit cell and crystal lattice.
  
• Under what conditions emf of a cell and terminal potential difference become equal?
• Write down two advantages of three phase AC supply.
• How does doubling the frequency of AC affect the reactance of:
  (a) An inductor.       
  (b) A capacitor?
• The anode of a diode is 0.2 V positive with respect to its cathode. I  s it forward biased?.
• What is the effect of forward and reverse biasing of a diode on the width of depletion region?
• What is the net charge on a n-type or a p-type substance? Justify the answer.

4. Attempt any SIX short questions. (6 X 2 = 12)

• What is a radioactive tracer? Describe one application in each case of medicine and agriculture.
• Is it possible to create a single electron from energy? Explain.
• How can the spectrum of hydrogen contain so many lines lives have elapsed?
• What fraction of a radioactive sample decays after two half lives have elapsed?
• If hail life of a nucleus is one year, does this mean that it will be completely decayed after two years? Explain.
• Which has the lower energy quanta? Radio waves or X-rays.
• What do we mean by critical mass?
• Is energy conserved when atom emits a photon of light?
• Give the two statements of uncertainty principle.

SECTION III

Attempt any THREE questions.  (8 x 3 = 24)

5. (a) What is meant by electrostatics? Apply electrostatics to explain Exerography.
(b) How many electrons pass through an electric bulb in one minute if 300mA current is passing through it?

6. (a) State and derive Faraday’s law of electromagnetic induction.
(b) Find the radius of an orbit of an electron moving at a rate of 2.0 x 10⁷ms^-1 in a uniform magnetic field of 1.20 x 10^-3T.

7. (a) Explain series resonance circuit and give its properties.
(b) What stress would cause a wire to increase the length by 0.01% if the Young’s modules or the wire is 1.2 x 10¹⁰ Pa. What force would produce this stress if the diameter of the wire is 0.56mm?

8. (a) State special theory of relativity with two postulates and explain two results:
(i) Time dilation
(ii) Length contraction.
(b) In a certain circuit the transistor has a collector current of 10m. A and base current 40μA. What is the  current gain of the transistor?

9. (a) Derive the relation for the quantized radii of hydrogen atom on the basis of bohr's model of hydrogen atom.
(b) The half-life  is 9.70 hours, Find its decay constant.

SECTION-IV

Attempt any THREE questions. (5x 3 = 15)

10.(a)

• Draw the table to find the resistance of wire by "Slide wire Bridge".
• How the Galvanometer is converted Into voltmeter?
• Draw the symbol and truth table of NAND Gate.
• Why the V-1 graph, for a lighted bulb is not a straight line?
• How can we test correctness of connections of 'Slide Wire Bridge"?
• Why a diode does not conduct when it is reverse biased?
• In photoelectric effect, by decreasing the distance between light bulb and photocell, current increases, why?
• What are practical uses of potentiometer?

(b) Write down brief procedure to determine the internal resistance of a cell using a potentiometer. OR
Write down brief procedure to study variation of current with the intensity of light in photoelectric affect.

(c) Answer the following questions on the basis of graph drawn below. Graph is plotted between capacitance and current on the back page at No. A.

• What do you conclude from this graph?
  
• Find the value of capacitance against 12 Ampere. OR
  Graph is plotted between voltage and resistance in case of resistance of voltmeter on the back page at No. B:             
• Find slope in this graph.
  
• Find the resistance-of voltmeter in this graph.