Physics Assignment CLASS = 12TH Unit –I “Electrostatics” Q1. State and explain coulomb’s law in Electrostatics. Q2. What is parallel plate Capacitor? Derive an expression for capacitance when dielectric slab is introduced between its plates. Q3. Define Dipole moment. Derive an expression for electric field intensity at a point on equatorial line of dipole. Q4. Derive expression for electric field intensity at a point on the axial line of Dipole. Q5. State Gauss’s theorem. Derive an expression for electric field intensity due to an infinite sheet of charge. Q6. What is meant by Conservation of charge? State and explain superposition principle. Q7. What capacitance is required to store an energy of 103 J. at a potential difference of 104 Volt? Q8. Derive an expression for Electric field intensity at a point near infinitely long straight charged wire. Q9. Derive expression for the torque acting on an electric dipole in a uniform electric field and specify its direction. Identify two pairs of perpendicular vectors in the expression. When the torque is minimum and maximum? Q10. Name and explain the theorem which relates the enclosed charge inside a closed surface with the electric flux through it. Q11. Define capacitance of a parallel plate capacitor. Derive an expression for the electrostatic energy stored in a charged capacitor. Q12. Give the properties of electric lines of forces. Q13. The electrostatic force on a small sphere of charge 0.4µc due to another small sphere of charge -0.8µc in air is 0.2N. a) What is the distance between the centre of two spheres? b) What is the force on the second sphere due to first? Q14. Define Electric potential and derive an expression for potential at a point due to an electric dipole. Q15. State Gauss’s theorem. Derive an expression for electric field intensity due to spherical shell. Q16. What is parallel plate capacitor. Derive expression for parallel plate capacitor when dielectric slab is inserted between its plate. Q17. Explain conservation of charge. Q18. What is the charge acquired by a body when one million electrons are transferred to it. Q19. An electric dipole consists of a positive and Negative charge of 5 µc each placed at distance of 7 mm. calculates the dipole moment. Q20. A capacitor whose capacitance is 20µF is charged to a potential of 2000 V. calculate its energy stored. Q21. An electric charge of 8.85 x 10-13 C is placed at the centre of a sphere of radius 1m. What is the total Electric flux linked with the sphere. Q22. What are the factors on which the capacitance of parallel plate capacitor depends? Q23. How many electrons are present in one coulomb of charge? Unit II – “Current Electricity” Q1. State and explain Kirchhoff’s laws. Q2. Give the condition for Wheatstone bridge to be most sensitive (Balance condition) Q3. A 25 watt and a 100 watt bulbs are joined in series and connected to mains. Which bulb will Grow brighter. Q4. Define Drift Velocity. Derive relation between current and drift vel. Q5. State ohm’s law and deduce it from the knowledge of drift vel. Q6. Discuss the effect of temp. on resistance. Q7. Explain colour code of carbon resistance. Q8. Define Electric power and Electric energy. Q9. Give relation between current and drift velocity. Q10. An electric bulb is marked 100w 230v. if the supply voltage drops to 115v, what is the heat and light produced by the bulb in 20 min. Q11. Calculate the resistivity of the material of a wire 1.0 m long, 0.4 mm diameter and having a resistance of 2Ω. Q12. A piece of wire having a resistance of 5Ω is stretched by double its original length. Calculate its new resistance. Q13. A 220V – 100W bulb is connected to 110V source. Calculate the power consumed by the bulb. Q14. How does the resistance and resistivity vary with temperature? OPTICS Q1. Find the relation between the radius of curvature and focal length of mirror. Q2. With the help of suitable ray diagram, derive the mirror formula for a concave mirror. Q3. Define magnification. Derive an expression for the magnification produced by a spherical mirror. Q4. Explain the phenomenon of polarization by reflection. State and explain Brewster’s law. Q5. Find the relation between real depth and apparent depth. Q6. Discuss refraction through a glass slab and show that emergent ray is parallel to the incident ray but displaced. Q7. Define total internal reflection and critical angle. Find the relation between critical angle and refractive index. Q8. What are Polaroids? Describe their uses briefly. Q9. What do you mean by the terms magnifying power and resolving power? Q10. Describe the diffraction of light at a single-slit. Q11. State and prove prism formula. Q12. What do you mean by angular dispersion and dispersive power? 𝜇 𝜇 𝜇 −𝜇 Q13. Deduce the relation 𝑣2 − 𝑢1 = 2 𝑅 1 where refraction takes place from rarer to denser medium (𝜇2 > 𝜇1 ) in case of a convex spherical surface and the image formed is virtual. Q14. What is lens formula? Derive it for a convex lens. Q15. What is meant by linear magnification of an image and obtain its expression in case of (a). Convex lens (b). Concave lens 1 𝑓 1 1 1 2 Q16. Derive the relation = 𝑓 + 𝑓 Q17. Explain Short sightedness and Long sightedness. Q18. Explain the working of a simple microscope and find an expression for its magnifying power. Q19. Draw a diagram for the formation of image by a compound microscope. Define its magnifying power and deduce an expression for it. Q20. Discuss Huygen’s hypothesis and explain the formation of wave-fronts. Q21. Deduce the laws of reflection on the basis of Huygen’s principle. Q22. What are Coherent source of light? What are the conditions for sustained interference? Q23. Discuss Young’s double-slit experiment to demonstrate interference of light. What are the conditions for dark and bright fringes? Q24. What is meant by diffraction of light? How does it differ from the interference of light?
