CBSE Class-12 Compartment Exam 2019 : Question Paper-Applied Physics
- Please check that this question paper contains 6 printed pages.
- Code number given on the right hand side of the question paper should be written on the title page of the answer-book by the candidate.
- Please check that this question paper contains 4 questions.
- Please write down the Serial Number of the question before attempting it.
- 15 minute time has been allotted to read this question paper. The question paper will be distributed at 10.15 a.m. From 10.15 a.m. to 10.30 a.m., the students will read the question paper only and will not write any answer on the answer-book during this period.
Instructions : Attempt all questions.
1. (a) State Coulomb’s law in electrostatics and hence define one Coulomb of electric charge. Define electric field strength at a point near a point charge and give its S.I. unit.
A sphere of radius 60 cm is charged to a potential of 1500 V.
(i) total electric charge on the sphere, and
(ii) electrical energy stored on the sphere.
(b) Define magnetic field strength at a point. Derive a mathematical relation for the magnetic field strength at the centre of a current carrying circular coil.
(c) Draw the atomic structures of ‘Ge’ and ‘Si’ atoms. How can these be made P-type and N-type extrinsic semi-conductor materials ? Explain briefly.
2. (a) On what factors does the force experienced by a moving point charge inside a uniform magnetic field depend ? Write the mathematical relation between this force and these factors. State the law which is used to determine the direction of this force.
A current carrying straight conductor is placed at an angle of 30º to a uniform magnetic field of strength 1·0 × 10–3 T. If the length of the conductor inside the magnetic field is 2 m and the current through it is 0·8 A, calculate the magnitude of the force experienced by the conductor.
(b) What are radio-isotopes ? Name any two radio-isotopes and give one use of each of these.
(c) What is a P-N junction ? Explain its behaviour under forward and reverse biasings by drawing circuit diagrams. Indicate the direction of movement of charge carriers.
3. (a) Define the ‘capacitance’ of a capacitor and write its S.I. unit. Establish a mathematical relation for the total capacitance of ‘n’ capacitors arranged in series.
(b) Distinguish between ‘nuclear fission’ and ‘nuclear fusion’. Give one example of each. Which one of these is used in a nuclear reactor for the release of energy ? Name any one nuclear fuel used in a nuclear reactor.
(c) With the help of a labelled circuit diagram, explain the use of a P-N junction diode as a ‘full wave rectifier’.
Explain the principle of working of an N-P-N transistor with the help of a neat circuit diagram. Show the movement of charge carriers through the junctions when these are suitably biased.
4. (a) State the Gauss theorem in electrostatics. Apply it to find the electric field strength at a point near a long uniformly charged straight conductor.
(b) Define the terms ‘magnetic field strength’, ‘magnetic flux density’ and ‘permeability’ of magnetic materials. Write their S.I. units.
(c) What are ‘radiation hazards’ ? Write four safety measures which can be taken to protect against these.
By which nuclear process is energy released in the Sun ? Why can’t this process be used to produce energy for commercial use ?