BISE Gujranwala · Class 12 · Physics · 2025 · First Annual · Group 2

1

1. 1

   The number of electron in one coulomb charge is equal to

   • (A)

     $1.6\times {10}^{-19}$ electron

   • (B)

     $6.25\times {10}^{-19}$ electron

   • (C)

     $6.25\times {10}^{18}$ electron

   • (D)

     $6.25\times {10}^{-19}$ electron

2. 2

   Charge carrier in electrolytes are

   • (A)

     Proton

   • (B)

     Electron

   • (C)

     Holes

   • (D)

     Positive and Negative ions

3. 3

   If the number of turns becomes double but length remains same, the magnetic field in the solenoid becomes

   • (A)

     Half

   • (B)

     Double

   • (C)

     Same

   • (D)

     Zero

4. 4

   Lenz's Law is in accordance with the Law of Conservation of

   • (A)

     Mass

   • (B)

     Momentum

   • (C)

     Charge

   • (D)

     Energy

5. 5

   In case of capacitor, the unit of reactance is

   • (A)

     Ohm

   • (B)

     mho

   • (C)

     Farad

   • (D)

     Henry

6. 6

   Which is crystalline solid?

   • (A)

     Zirconia

   • (B)

     Glassy Solid

   • (C)

     Natural Rubber

   • (D)

     Polystyrene

7. 7

   For rectification, we use

   • (A)

     Transformer

   • (B)

     Diode

   • (C)

     Choke

   • (D)

     Generator

8. 8

   The rest mass of Photon is

   • (A)

     Infinite

   • (B)

     $1.6\times {10}^{-27}$ Kg

   • (C)

     Zero

   • (D)

     $3\times {10}^8$ Kg

9. 9

   The units of Rydberg's constant is

   • (A)

     ${\mathrm{m}\mathrm{s}}^{-1}$

   • (B)

     m

   • (C)

     ${\mathrm{N}\mathrm{m}}^{-2}$

   • (D)

     ${\mathrm{m}}^{-1}$

10. 10

    Neutron was discovered in 1932 by

    • (A)

      Bohr

    • (B)

      Chadwick

    • (C)

      Dirac

    • (D)

      Fermi

11. 11

    The concept of electric field was given by

    • (A)

      Faraday

    • (B)

      Henry

    • (C)

      Michelson

    • (D)

      Orested

12. 12

    Tesla is a unit of

    • (A)

      Flux density

    • (B)

      Magnetic flux

    • (C)

      Self-inductance

    • (D)

      Mutual inductance

13. 13

    The self-inductance is given by

    • (A)

      $NL=\phi I$

    • (B)

      $NI=L\phi$

    • (C)

      $N\phi =LI$

    • (D)

      $N=LI$

14. 14

    Capacitive reactance $X_c=$ $\underset{‾}{}$

    • (A)

      $2\pi fC$

    • (B)

      $\frac{1}{2\pi fC}$

    • (C)

      $4\pi fC$

    • (D)

      $\frac{1}{4\pi fC}$

15. 15

    Conversion of A.C into D.C is called

    • (A)

      Modulation

    • (B)

      Oscillation

    • (C)

      Amplification

    • (D)

      Rectification

16. 16

    Albert Einstein was awarded Nobel Prize in

    • (A)

      1918

    • (B)

      1921

    • (C)

      1905

    • (D)

      1911

17. 17

    One amu is equal to

    • (A)

      931. Mev

    • (B)

      9.31 Mev

    • (C)

      93.1 Mev

    • (D)

      0.931 Mev

2

1. (i)

   How can you identify that which plate of a capacitor is positively charged?

2. (ii)

   Is $\vec{E}$ necessarily zero inside a charged rubber balloon if balloon is spherical? Assume that charge is distributed uniformly over the surface.

3. (iii)

   Why circuits of sensitive electronic devices such-as T.V and computers are often enclosed within metal boxes?

4. (iv)

   Define electron volt. Also write its value.

5. (v)

   Is it possible to orient a current loop in a uniform magnetic field such that the loop will not tend to rotate? Explain.

6. (vi)

   What should be the orientation of a current carrying coil in a magnetic field so that torque acting upon the coil is (a) Maximum (b) Minimum?

7. (vii)

   Explain Right Hand Rule to find the direction of magnetic field around a current carrying conductor.

8. (viii)

   Define ammeter. How a galvanometer is converted into an ammeter?

9. (ix)

   What do we mean by the term critical mass?

10. (x)

    A particle which produces more ionization is less penetrating. Why?

11. (xi)

    What are the biological effects of low level radiation and high levels of radiation.

12. (xii)

    Define mass defect and binding energy.

3

1. (i)

   Describe a circuit which will give-a continuously varying potential.

2. (ii)

   Why does the resistance of a conductor rise with temperature?

3. (iii)

   What is thermistor? How it can be used to measure low temperature, especially at near $10\mathrm{k}$?

4. (iv)

   Write down the name of device that will (a) permit flow of direct current but oppose the flow of alternating current (b) permit flow of alternating current but not the direct current

5. (v)

   Explain the conditions under which electromagnetic waves are produced from a source.

6. (vi)

   Write down two merits of frequency modulation.

7. (vii)

   Distinguish between intrinsic and extrinsic semiconductor.

8. (viii)

   Why magnetic materials are not ferromagnetic above Curie temperature?

9. (ix)

   What is the role of domains in magnetizing the material to saturation?

10. (x)

    What is the net charge on a n-type or a p-type substance?

11. (xi)

    Why ordinary silicon diodes do not emit light?

12. (xii)

    If the potential difference between two inputs of inverting amplifier with open loop-gain of ${10}^5$ is $1\mathrm{m}\mathrm{v}$. What will be output voltage?

4

1. (i)

   Define motional emf and write its relation.

2. (ii)

   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?

3. (iii)

   Can a D.C motor be turned into a D.C generator? What changes are required to be done?

4. (iv)

   State Stefen-Boltzmann law and write its relation.

5. (v)

   What is the energy of a photon in a beam of infrared radiation of wavelength $1240\mathrm{n}\mathrm{m}$?

6. (vi)

   If an electron and a proton have the same de-Broglie wavelength, which particle has greater speed?

7. (vii)

   We do not notice the de-Broglie wavelength for a pitched cricket ball. Explain why?

8. (viii)

   What is meant by population inversion?

9. (ix)

   What do we mean when we say that the atom is excited?

1. 5(a)

   State and explain Kirchhoff's Second Rule.

   (5)
2. 5(b)

   Two point charges, $q_1=-1.0\times {10}^{-6}\mathrm{C}$ and $q_2=+4.0\times {10}^{-6}\mathrm{C}$ are separated by a distance of $3.0\mathrm{m}$. Find and justify the zero-field location.

   (3)
3. 6(a)

   State and prove Faraday's Law of electromagnetic induction.

   (5)
4. 6(b)

   What current should pass through a solenoid that is $0.5\mathrm{m}$ long with $10,000$ turns of copper wire so that it will have a magnetic field of $0.4\mathrm{T}$?

   (3)
5. 7(a)

   What is rectification? Explain full wave rectification. How pulsating output voltage is made smooth?

   (5)
6. 7(b)

   A circuit has an inductance of $\frac{1}{\pi }\mathrm{H}$ and resistance of $2000\mathrm{\Omega }$. A $50\mathrm{H}\mathrm{z}$ A.C is supplied to it. Calculate the reactance and impedance offered by the circuit.

   (3)
7. 8(a)

   Explain Strain Energy in deformed material. Use graphical method to determine work done by force.

   (5)
8. 8(b)

   What is the energy of a photon in a beam of infrared radiation of wavelength $1240\mathrm{n}\mathrm{m}$?

   (3)
9. 9(a)

   In case of Hydrogen Atom, derive the relations for its (i) Quantized Radii (ii) Quantized Energies

   (5)
10. 9(b)

    The half-life of ${}_{38}{\mathrm{S}\mathrm{r}}^{91}$ is $9.70$ hours. Find its decay constant.

    (3)