Deendayal Upadhya Gorakhpur University 2007 set 1 - exam paper

Physics - 2007 (Set I - Delhi)



Q. 1. An electron, an alpha-particle and a proton have the identical kinetic energy. Which 1 of these particles has the largest de-Broglie wavelength ? 1

Q. 2. Why should the material used for making permanent magnets have high coercivity? 1

Q. 3. The radioactive isotope D decays according to the sequence

If the mass number and atomic number of D2 are 176 and 71 respectively, what is (i) the mass number (ii) atomic number of D ? 1

Q. 4. What will be the values of input A and B for the Boolean expression? 1

Q. 5. Why is frequency modulation perferred over amplitude modulation for transmission of music? 1

Q. 6. The output of an OR gate is connected to both the inputs of a NAND gate. Draw the logic circuit of this combination of getes and write its truth table. 2

Q. 7. Draw a plot of potential energy of a pair of nucleons as a function of their separation. What is the significance of negative potential energy in the graph drawn ? 2

Q. 8. A convex lens of refractive index 1.5 has a focal length of 18 cm in air. compute the change in its focal length when it is immersed in water of refractive index . 2

Q. 9. Distinguish ranging from the terms 'average value' and 'rms value' of an alternating current. The instantaneous current from an a.c. source is I = five sin (314 t) ampere. elaborate the avg. and rms values of the current ? two

Q. 10. Write the relation for the forece acting on a charge carrier q moving with a velocity through a magnetic field in vector notation. Using this relation, deduce the conditions under which this force will be (i) maximum (ii) minimum. 2

Q. 11. A cylindrical metallic wire is stretched to increase its length by 5%. compute the percentage change in its resistance. 2

Q. 12. The electric field E due to a point charge at any point near it is described as where q is the test charge and F is the force acting on it. What is the physical significance of in this expression ? Draw the electric field lines of a point charge Q when (i) Q > 0 and (ii) Q < 0. 2

Or

describe electric flux. Write its S.I. units. A spherical rubber balloon carries a charge that is uniformly distributed over its surface. As the balloon is blown up and increases in size, how does the total electric flux coming out of the surface change ? provide cause.

Q. 13. Deduce an expression for the electric potential due to an electric dipole at any point on its axis. Mention 1 contrasting feature of electric potential of a dipole at a point as compared to that due to a single charge. 3

Earning:   Approval pending.