Nt1310 Unit 4

Part III PHYSICS HSE II Time:2Hours Max:60 Scores 1. Three identical charges each +q are placed at the corners of an equilateral triangle of side d cm. Calculate the force on a +ive charge +2q at the centroid of the triangle. 2 2.If the earth is supposed to be a metallic sphere,its capacity will be nearly (a) 700pf (b) 700 microfarad (c) 700f (d) 6.4 X10^6 f 1score 3. write the relation between dielectric constant and electric susceptibility. 1score 4. A box encloses an electric dipole consisting of charge 5micro C and -5micro C and of length 10cm. What is the total electric flux through the box? 2scores 5. Find the ratio of the p.d that must be applied across the (1)parallel (2) series combination of two identical capacitors so that the energy stored in the two cases becomes the same. 2 scores 6.(a)
1 score (b)Estimate the steady state current in the 2ohm resistor as show in fig . The internal resistance of the battery is negligible . 2 score

7. Define the term current density of a metallic conductor .deduce the relation connecting current density (J)and Conductivity ( )of the conductor ,when an electric field E, is applied to it. 3scores 8. How are the following e.m. radiations produced , mention one used of them.? (1)Microwaves (2) Ultra – violet rays (3) gamma rays 3scores 9. How does an air bubble behaves inside water? 10. State the principle on which induction coil is constructed. 1 score 1score

11. A man is shaving with his chin 0.4m from a concave magnifying mirror. If the linear magnification is 2.5. What is the radius of curvature of the mirror ? 2