Gujranwala Board 2013
 Physics
Time : 20 Minutes
PARER-II
(Objective Type)
Marks : 17
Note: You have four choices for each objective type question as A, B, C and D. The choice which you think is correct, fill that circle in front of that question number with marker or pen on the Answer Book provided, Cutting or filling two or more circles will result in zero mark in that question Attempt as many question as given in objective type question paper and leave others blank.

• At resonance RLC series circuit shows the behaviour of
  
  (A) pure resistive circuit
  (B) pure capacitive circuit
  (C) pure inductive circuit
  (D) pure RLC circuit 
  
  
• Magnetic potential energy stored in an inductor depends upon 
  
  (A) under root of the value of current
  (B) cube root of the value of current
  (C) cube root of the value of current
  (D) square of the value of current 
  
  
• Fluorescence is the property of 
  
  (A) high frequency particles
  (B) moderate frequency particles
  (C) low frequency particles
  (D) visible light
  
  
• The reverse process of photo-electric effect is 
  
  (A) Compton effect
  (B) X-rays production
  (C) pair production
  (D) pair annihilation 
  
  
• Base of the transistor is very thin of the order f
  
  (A) 10-2 m
  (B) 10-4 m
  (C) 10-6 m
  (D) 10-8 m 
  
  
• A student has five resistances each of value Ω The minimum resistance that can be obtained by combining them in parallel is
  
  (A) 1/50 Ω
  (B) 1/25 Ω
  (C) Ω
  (D) 5 Ω
  
  
• Energy density in case of a capacitor is always proportional to
  
  (A) E²
  (B) ?_°
  (C) V²
  (D) C
  
  By using NAVSTAR speed of an object can now be determined to an accuracy of
  
  (A) 20 cm/sec
  (B) 760 cm/sec
  (C) 50 cm/sec
  (D) 2 cm/sec
  
  
• Maximum emf generated in a generator is
  
  (A) ?= ? sin
  (B) ? = ?_° sin
  (C) ? =N AB sin
  (D) ?_° = N AB
  
  
• An avometer is also called
  
  (A) an ammeter
  (B) a voltmeter
  (C) a multimeter
  (D) an ohm-meter
  
  
• If an electron of charge is accelerated through a potential difference V, it will acquire energy
  
  (A) Ve
  (B) V/₂
  (C) E/₂
  (D) Ve₂
  
  
• Extremely penetrating particles are
  
  (A) neutrons
  (B) a - particles
  (C) β - particles
  (D) - particles
  
  
• If fingers of right hand show the direction of magnetic field and palm shows the direction of force Then thumb points for
  
  (A) torque
  (B) voltage
  (C) current
  (D) induced emf
  
  
• At high frequency, RLC series circuit shows the behaviour of
  
  (A) pure inductive circuit
  (B) pure resistive circuit
  (C) pure capacitive circuit
  (D) pure RLC circuit
  
  
• The substances with conductivities between 10^-10 and 10^-20 (Ωm)^-1 are called
  
  (A) super conductors
  (B) insulators
  (C) semi conductors
  (D) conductors
  
  
• If a. platinum wire is heated to 500°C, then it appears as
  
  (A) white
  (B) yellow
  (C) orange red
  (D) dull red
  
  

Universal gate is the gate which can perform the function of

(A) buffer gate
(B) any logic gate
(C) any basic
(D) any exclusive gate

Physics
Subjective
PARER-II
Maximum Marks: 63
(SECTION-I)

2.Write short answers to any EIGHT (8) questions: 16

• Define electron volt.
• Do electrons tend to go to region of high potential or of low potential?
• Suppose that you follow an electric field line due to a positive point charge. Do electric field and potential increase or decrease?
• Explain the term 'potential gradient'.
• Describe the change in magnetic field inside solenoid carrying a steady current I, if length of solenoid is doubled but number of turns remains the same.
• Why does the picture on TV screen become distorted when a magnet is brought near the screen?
• What is meant by the term 'meter movement'?
• Give two uses of CRO.
• Define henry.
• Describe Lenz's Law.
• A square loop of wire is moving through a uniform magnetic field. The normal to loop is oriented parallel to magnetic field. Is emf induced in loop? Give a reason for your answer.
• Does the induced emf always act to decrease the magnetic flux through a circuit?

3. Write short answers to any EIGHT (8) questions: 16

• What are thermisters? Give their uses.
• Do bends in a wire affect its electrical resistance? Explain.
• Describe a circuit which gives a continuously varying potential.
• Write the uses of super conductors.
• How does doubling the frequency affect the reactance of (a) inductor (b) capacitor?
• What is meant by paramagnetic substances? Give examples.
• What is meant by A.M. and F.M?
• Define impedance and resonance frequency.
• What is meant by hysteresis loss? How is it used in the construction of a transformer?
• Why charge carriers are not present in the depletion region?
• What is the net charge on a n-type or a p-type substance?
• What is the effect of reverse biasing and orward biasing of a diode on the width of depletion region?

4.Write short answers to any SIX (6) questions: 12

• Will higher frequency light eject greater number of electrons than low frequency light? Explain briefly.
• Is it possible to create a single electron from energy? Explain.
• What is de-Broglie wavelength of a particle of mass 5.0 mg moving with 8 ms^-1? (h = 6.63 x 10^-34 Js)
• What is the difference between excitation of an atom by (a) a photon (b) an electron?
• How can the spectrum of hydrogen contain so many lines when hydrogen contains one electron?
• A particle which produces more ionization is less penetrating. Why?
• Why does a Geiger Muller tube for detecting 7-rays not need a window at all?
• By using E = mc² show that 1.66 x 10^-27 kg = 931 MeV
• Explain briefly critical mass of fissionable material.

(SECTION-II)

Question#5

(a) Define capacitor. Find an epressien for the capacitance of a parallel plate capacitor. 5
(b) The potential difference between the terminals of a battery in open circuit is 2.2 volts. When it is connected across a resistance of 5 ohm, the potential falls to 1.8 volts. Calculate the current and internal resistance of the battery. 5

Question#6

(a) Find force on a moving charge in magnetic field.
(b)A D.C. motor operates at 240 volts and has a resistance of 0.5 Ω. When the motor is running at normal speed, the armature current is 15.A. Find back emf in the armature.

Question#7

(a)Describe the formation of energy bands in solids. Explain the difference amongst electrical behaviour of conductors, insulators and semi-conductors in terms of energy band theory. 1,2,2
(b) Find the value of the current flowing through a capacitor 0.5 μF when connected to a source of 150 Vat 50 Hz. 3

Question#8

(a) What is semi-conductor diode? Explain its behaviour when it is forward biased and reversed biased. 5
(b)What is the de-Broglie wavelength of an electron whose K.E. is 120 eV? 3

Question#9

(a) Give the postulates of Bohr's model of the hydrogen atom and derive the quantized radii of hydrogen atom. 5
(b) Determine the energy associated with the following reaction. 3

 14;→ ¹⁴₇N+0_-1e
  6^C

(Mass of ¹⁴C = 14.0077u)

(Mass of ¹⁴N = 14.0031u)

(Mass of °_-le C = 0.0055u)