Electricity and Magnetism — DU B.Sc. (Prog.) Physical Science courses pertaining to Electronics Previous Year Question Papers

(a) Define the electric flux. A square frame of edge 10 cm is placed with a positive normal making an angle of 60° with a uniform electric field of 20 V/m, find the flux of the electric field through the surface bounded by the frame. (b) What is Displacement Current? (c) Define Magnetic permeability and susceptibility. Establish the relation 4 = Mo (1 + X). (d) Calculate the coefficient of self-induction of a coil of 1000 turns when a current of 2.5 Ampere produces a magnetic flux of 0.5 micro-Weber. (e) State Kirchhoff's Current and Voltage law. 2. (a) State and prove Gauss's theorem in electrostatics. (b) What is the potential at the center of the square, if the four charges are placed at the corner of the square: 9, = +1.0x10-8C, 92=-2.0 x 10-8C, 93= +3.0 × 10-8C, 94=+2.0 x 10-8 C and side of square is 1.0 meter. (5) (c) The voltage between parallel plates of a capacitor is Vy. The plates are isolated electrically. A dielectric slab of dielectric constant k is inserted between the plates and completely fills the volume between them. Find the new potential V (3) KALINDI COLLEGE LiBRARY 3. (a) State and explain Biot-Savart's law. Derive an expression for the magnetic field at a point due to an infinitely long straight current carrying conductor using Biot-Savart's law. (7) (b) What are the characteristics of diamagnetic, paramagnetic and ferromagnetic substances. Illustrate by simple experiment. (5) (c) A 10 cm long wire carrying a current of 10 ampere is held at an angle 30° with the direction of a uniform magnetic field strength of 1 weber/metre?. Calculate the force acting on wire. (3) (a) Explain the phenomenon of self-induction. Derive an expression for the coefficient of self-inductance of a long uniformly wound solenoid. Hence find the self-inductance of a toroidal coil of circular cross-section of radius r. (7) (b) Calculate the mutual-inductance of a solenoid of 1 metre length having 500 turns in primary and 100 turns in secondary coil and the area of cross-section of solenoid is 5 cm?. (5) (c) Write the equation of continuity and explain its physical significance. (3) 5. (a) State the maximum power transfer theorem. Show that power lost in the internal generator is equal to the power delivered to the load and the power efficiency is only 50%. (7) (b) Draw the Thevenin's equivalent for the following circuit. Calculate the current through the load resistance. (5) (c) State and explain Norton's Theorem with example. Ho = 4T × 10- henry/metre (free space) €o = 8.85 x 10-12 C2/N.m? (free space)