Series OSS Code No. 105
APPLIED PHYSICS
(Theory)
Time allowed : 3 hours Maximum Marks : 60
1. (a) State Gauss’ theorem in electrostatics. Apply it to find the electric ifeld strength at a point near a long straight conductor carrying electric charge. 6
OR
What is the magnitude of a point electric charge, chosen so that the electric field due to it at a point 50 cm away has magnitude 2.0 NC-1? 6
(b) Derive a mathematical expression for the magnetic field strength at the centre of a circular coil carrying electric current. 5
(c) Draw the electronic configuration in the atomic structures of ‘Ge’ and ‘Si’ atoms. How can these be made T type’ and ‘N-type’ semi-conductors ? 4
2. (a) Define the terms : ‘magnetic field strength’, ‘magnetic flux density’ and ‘permeability’ of a magnetic material. Write their SI units. 5
OR
A current carrying conductor is placed at an angle of 30° to a uniform magnetic field of strength 2 x 103 T. The length of the conductor inside the magnetic field is 2 m and the current flowing through it is 1.6 A. Calculate the magnitude of the force experienced by it. 5
(b) Distinguish between ‘nuclear fission’ and ‘nuclear fusion’. Which one of them is used for release of energy in a nuclear reactor ? Name one fuel used in a nuclear reactor. 6
(c) With the help of a circuit diagram, explain the working of a P-N-P transistor. 4
3. (a) Define the term ‘capacitance’ of a capacitor. Derive an expression for the total capacitance of ‘n’ capacitors arranged in series. 5
(b) On what factors does the force experienced by a moving electric charge inside a magnetic field depend ? Write the corresponding mathematical expression for this force. State the rule used for determining the direction of this force. 6
(c) What are intrinsic and extrinsic semi-conductors ? How does the rise in temperature affect the conductivity of semi-conductors ? 4
OR
What is a P-N junction ? How does it behave under forward and reverse bias ? Explain with the help of circuit diagrams.
4. (a) Define electric potential at a point due to a :point charge. Write its SI unit. Derive an expression for the electric potential at a point outside a charged sphere. 5
(b) What are radiation hazards ? Mention four safety measures which should be taken against radioactive radiations. 6
OR
What are radio isotopes ? Write their any four uses. 6
(c) Explain the working of a full wave rectifier using semi-conductor diodes, with the help of a labelled circuit diagram. 4
Physical Constants
ε ◦ = 8.854 x 10-12 Fm-1
µo = 4∏ x 10-7 Hm-1
Charge on an electron = 1.6 x 10-19 C
1 = 9 x 10-9 Nm2 C-2
4∏ ε ◦