BISE Gujranwala · Class 12 · Physics · 2025 · Group 1

1. 1.1

   The electrical potential at the mid point in an electric dipole is

   • (A)

     $0\mathrm{V}$

   • (B)

     $0.5\mathrm{V}$

   • (C)

     $1.0\mathrm{V}$

   • (D)

     $1.5\mathrm{V}$

2. 2

   Selenium is a

   • (A)

     Conductor

   • (B)

     Insulator

   • (C)

     Semiconductor

   • (D)

     Photoconductor

3. 3

   Kirchhoff's $1$st rule is the manifestation of law of conservation of

   • (A)

     Mass

   • (B)

     Momentum

   • (C)

     Charge

   • (D)

     Energy

4. 4

   When a charge particle is projected parallel to a uniform magnetic field, its path or trajectory will be

   • (A)

     Straight line

   • (B)

     Circular

   • (C)

     Helical

   • (D)

     Elliptical

5. 5

   The effective way to increase the sensitivity of a galvanometer is to

   • (A)

     Increase the number of turns

   • (B)

     Increase the magnetic field strength

   • (C)

     Increase the area of coil

   • (D)

     Decrease the area of coil

6. 6

   When the motor is just started, the back emf is

   • (A)

     Maximum

   • (B)

     Minimum

   • (C)

     Almost zero

   • (D)

     Equal to current

7. 7

   The working principle of alternating current generator is

   • (A)

     Coulomb's law

   • (B)

     Faraday's law

   • (C)

     Lenz's law

   • (D)

     Ampere's law

8. 8

   The slope of $q$-$t$ curve at any instant of time when A.C passes through a capacitor represents

   • (A)

     Voltage

   • (B)

     Inductance

   • (C)

     Impedance

   • (D)

     Current

9. 9

   The impedance of series resonance circuit at resonance is

   • (A)

     Zero

   • (B)

     Resistive

   • (C)

     Capacitive

   • (D)

     Inductive

10. 10

    A solid having regular arrangement of atoms or molecules is called

    • (A)

      Crystalline solid

    • (B)

      Amorphous solid

    • (C)

      Polymeric solid

    • (D)

      Glassy solid

11. 11

    A photodiode can turn its current ON and OFF in

    • (A)

      Milliseconds

    • (B)

      microseconds

    • (C)

      nanoseconds

    • (D)

      picoseconds

12. 12

    $X=A\cdot \bar{B}+\bar{A}\cdot B$ is the mathematical notation for

    • (A)

      NOR gate

    • (B)

      NAND gate

    • (C)

      XOR gate

    • (D)

      XNOR gate

13. 13

    The wavelength associated with an electron moving with a speed of $1.0\times {10}^6\mathrm{m}{\mathrm{s}}^{-1}$ is

    • (A)

      $7.3\times {10}^{-10}\mathrm{m}$

    • (B)

      $7.3\times {10}^{-11}\mathrm{m}$

    • (C)

      $6.5\times {10}^{-10}\mathrm{m}$

    • (D)

      $6.5\times {10}^{-11}\mathrm{m}$

14. 14

    When the platinum wire is heated, it becomes white at about

    • (A)

      $900{}^{\circ }\mathrm{C}$

    • (B)

      $1100{}^{\circ }\mathrm{C}$

    • (C)

      $1300{}^{\circ }\mathrm{C}$

    • (D)

      $1600{}^{\circ }\mathrm{C}$

15. 15

    $K_{\beta }$ X-rays are produced due to transition of electron from

    • (A)

      K to L shell

    • (B)

      L to K shell

    • (C)

      M to K shell

    • (D)

      M to L shell

16. 16

    The binding energy per nucleon is maximum for

    • (A)

      Uranium

    • (B)

      Helium

    • (C)

      Barium

    • (D)

      Iron

17. 17

    The decayed fraction of a radioactive element after two half lives is

    • (A)

      $\frac{1}{2}$

    • (B)

      $\frac{1}{4}$

    • (C)

      $\frac{3}{4}$

    • (D)

      $\frac{7}{8}$

Q.2

1. i

   The potential is constant throughout a given region of space. Is electric field zero or non-zero in this region?

2. ii

   Do electrons tend to go to the region of high potential or low potential?

3. iii

   Define capacitance with units.

4. iv

   Define the relative permittivity ${\epsilon }_r$.

5. v

   If a charge particle moves in a straight line through some region of space, is magnetic field zero there?

6. vi

   Why does the picture of a T.V. screen becomes distorted, when a magnet is brought near the screen?

7. vii

   Why a Voltmeter is used in parallel?

8. viii

   Define sensitivity of a galvanometer.

9. ix

   Why heavy nuclei are unstable?

10. x

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

11. xi

    Write down the names of six quarks with charge.

12. xii

    What do you mean by equivalent doze $(\mathrm{D}\mathrm{e})$? Explain.

Q.3

1. i

   Do bends in a wire affect its electrical resistance? Explain.

2. ii

   What are the difficulties in testing whether the filament of a lighted bulb obeys Ohm's Law?

3. iii

   What is meant by A.M and F.M?

4. iv

   In a R-L, circuit, will the current Lag or Lead the voltage? Illustrate your answer by a vector diagram.

5. v

   Distinguish between amorphous and polymeric solids.

6. vi

   Differentiate between tensile and shear modes of stress and strain.

7. vii

   Why ordinary silicone diodes do not emit light?

8. viii

   Why is the base current in a transistor very small?

9. ix

   Write down the truth table of XNOR gate.

10. x

    Write down uses of superconductors (only three).

11. xi

    What is choke? Write down its uses.

12. xii

    What is meant by "Tolerance"? Give example.

Q.4

1. i

   A square loop of wire is moving through a uniform magnetic field. The normal to the loop is oriented parallel to the magnetic field. Is an emf induced into the loop? Write down a reason for your answer.

2. ii

   Does the induce emf always act to decrease the magnetic flux through a circuit?

3. iii

   State Faraday's Law. Also write down its mathematical relation.

4. iv

   As a solid is heated and begins to glow. Why does it first appear red?

5. v

   Which has lower energy quanta? Radio waves or X-rays.

6. vi

   State Position-Momentum Uncertainty Principle and give its mathematical form.

7. vii

   Write down the postulates of special theory of relativity.

8. viii

   Is energy conserved when we say that the atom is said to be excited?

9. ix

   Differentiate between $K_{\alpha }$ and $K_{\beta }$ X-rays.

SECTION-II

1. Q.5
2. (a)

   What is electric polarization? Explain how polarization affects the capacitance of parallel plate capacitor.

   (5)
3. (b)

   How many electrons pass through an electric bulb in one minute if $300\mathrm{m}\mathrm{A}$ current is passing through it?

   (3)
4. Q.6
5. (a)

   State and explain Lenz's Law.

   (5)
6. (b)

   Find the value of the magnetic-field that will cause a maximum force of $7.0\times {10}^{-3}\mathrm{N}$ on a $20.0\mathrm{c}\mathrm{m}$ straight wire carrying a current of $10.0\mathrm{A}$

   (3)
7. Q.7
8. (a)

   Explain the flow of A.C through an inductor and discuss the phase relationship between current and voltage.

   (5)
9. (b)

   The current flowing into the base of a transistor is $100\mu \mathrm{A}$. Find its collector current $I_c$, its emitter current $I_E$ and the ratio $\frac{I_c}{I_E}$ if the value of current gain $\beta$ is $100$.

   (3)
10. Q.8
11. (a)

    State the Broglie Hypothesis. How did Davisson and Germer prove it experimentally?

    (5)
12. (b)

    A $1.25\mathrm{c}\mathrm{m}$ diameter cylinder is subjected to a load of $2500\mathrm{K}\mathrm{g}$. Calculate the stress on the bar in mega pascals.

    (3)
13. Q.9
14. (a)

    What is Nuclear Reactor? Describe the function of its main parts.

    (5)
15. (b)

    Calculate the longest wavelength of radiation for the Paschen Series

    (3)