Chapter 2: ELECTRIC POTENTIAL AND CAPACITANCE for AHSEC Class 12 Physics

Some probable questions from Chapter 2: Electric Potential and Capacitance for AHSEC Class 12 Physics, based on recent trends and previous years' papers:

---

Short Answer Type (1-2 Marks)

1. Define electric potential at a point. What is its SI unit?
2. Define potential difference between two points.
3. Define electrostatic potential energy.
4. What is an equipotential surface? Give an example.
5. What is the relation between electric field and electric potential?
6. Can two equipotential surfaces intersect each other? Justify your answer.
7. Why is the electric field zero inside a conductor?
8. Write an expression for the capacitance of a parallel plate capacitor.
9. What is a dielectric constant? How does it affect the capacitance of a capacitor?
10. Define farad. How is it related to other units of capacitance?

---

Short Derivation/Numerical Type (3-4 Marks)

11. Derive an expression for the electric potential at a point due to a point charge.
12. Derive an expression for the potential energy of a system of two point charges.
13. Derive an expression for the capacitance of a parallel plate capacitor with a dielectric medium.
14. What is a Van de Graaff generator? Explain its principle of operation.
15. Show that the work done in moving a charge between two points on an equipotential surface is zero.
16. Derive an expression for the energy stored in a charged capacitor.
17. A parallel plate capacitor has a plate area of 1m² and a plate separation of 1mm. If the dielectric medium between the plates is air, find its capacitance.
18. A capacitor of 5μF is charged to 10V. Calculate the energy stored in it.
19. A 20μF capacitor is connected in series with a 10μF capacitor. Find the equivalent capacitance.
20. Three capacitors of 4μF, 6μF, and 12μF are connected in parallel. Find the total capacitance.

---

Long Answer Type (5-6 Marks)

21. Explain the concept of electric potential due to a point charge and derive its expression.
22. Derive the expression for the capacitance of a spherical capacitor.
23. What is a capacitor? Explain how capacitors are connected in series and parallel and derive their equivalent capacitance formulas.
24. Explain the principle and working of a Van de Graaff generator with a neat diagram.
25. Derive the expression for the energy density of an electric field in a capacitor.

Chapter 1: Electric Charges and Fields for AHSEC Class 12 Physics

 Here are some probable questions from Chapter 1: Electric Charges and Fields for AHSEC Class 12 Physics, based on recent trends and previous years' papers:

Short Answer Type (1-2 Marks)

1. State and explain the principle of superposition of electric forces.
2. Define electric field intensity. What is its SI unit?
3. Define electric dipole moment. Write its SI unit.
4. State Gauss's law in electrostatics.
5. What is the physical significance of electric flux?
6. Write two properties of electric field lines.
7. What is meant by electrostatic shielding?
8. State the conditions for a charge distribution to be in equilibrium.
9. What is the effect of a dielectric medium on Coulomb’s force?
10. Define quantization of charge and state its mathematical expression.

Short Derivation/Numerical Type (3-4 Marks)

11. Derive the expression for the electric field due to a point charge.
12. Derive an expression for the torque acting on an electric dipole in a uniform electric field.
13. Prove that the total electric flux through a closed surface enclosing a charge is independent of the shape or size of the surface.
14. Derive an expression for the electric field at an axial point of an electric dipole.
15. Derive an expression for the electric field at a point on the equatorial line of a dipole.
16. Using Gauss’s law, derive an expression for the electric field due to a long straight charged wire.
17. Using Gauss’s law, derive an expression for the electric field due to a uniformly charged infinite plane sheet.
18. A charge of $2 \times 10^{-9} C$ is placed in vacuum. Calculate the electric field at a distance of 30 cm from the charge.
19. Two charges, +5μC and -5μC, are separated by 10 cm. Calculate the electric field at a point 5 cm away from the midpoint of the dipole along its axial line.
20. A square of side 10 cm has charges of +2μC, -2μC, +2μC, and -2μC placed at its four corners. Find the resultant electric field at the center.

Long Answer Type (5-6 Marks)

21. Derive an expression for the potential energy of an electric dipole in a uniform electric field.
22. Explain the concept of continuous charge distribution and derive an expression for the electric field due to a uniformly charged ring.
23. Derive an expression for the electric field due to a charged spherical shell at (i) a point outside the shell and (ii) a point inside the shell.
24. Explain the concept of electric flux and derive the relation between electric field and flux using Gauss’s law.
25. Explain how an electric field is defined using Gauss’s law for a uniformly charged spherical conductor.

Chapter 14: Semiconductors for AHSEC Class 12 Physics

Here are some probable questions from Chapter 14: Semiconductors for AHSEC Class 12 Physics, based on recent trends and previous years' papers:

---

Short Answer Type (1-2 Marks)

1. Define energy band and energy gap in a solid.
2. What is a semiconductor? Give two examples.
3. Differentiate between intrinsic and extrinsic semiconductors.
4. What is doping? Why is it necessary for semiconductors?
5. What is the difference between p-type and n-type semiconductors?
6. What is a depletion layer in a p-n junction?
7. Define knee voltage in a p-n junction diode.
8. What is rectification? How does a diode act as a rectifier?
9. Write two differences between conductors, semiconductors, and insulators.
10. What is meant by drift current and diffusion current in a semiconductor?

---

Short Derivation/Numerical Type (3-4 Marks)

11. Explain the formation of the depletion region in a p-n junction diode.
12. Draw and explain the V-I characteristics of a p-n junction diode in forward and reverse bias.
13. Explain the working of a full-wave rectifier with a circuit diagram.
14. Explain how a transistor can be used as an amplifier.
15. What is a Zener diode? Explain its use as a voltage regulator.
16. Derive an expression for the conductivity of a semiconductor in terms of charge carrier concentration.
17. Draw and explain the circuit diagram of a common-emitter amplifier.
18. Explain how light-emitting diodes (LEDs) work.
19. Calculate the current flowing through a diode when a 0.7V forward voltage is applied across a silicon p-n junction.
20. In an n-type semiconductor, the electron concentration is 5 × 10¹⁶ cm⁻³ at 300K. If the intrinsic carrier concentration is 1.5 × 10¹⁰ cm⁻³, calculate the hole concentration.

---

Long Answer Type (5-6 Marks)

21. Explain the energy band theory of solids and classify materials into conductors, semiconductors, and insulators based on it.
22. With a neat diagram, explain the working of a photodiode.
23. Explain the working principle of a solar cell.
24. What are logic gates? Explain AND, OR, and NOT gates with truth tables and logic circuit diagrams.
25. Describe the working of a common-base transistor amplifier with a circuit diagram.