Slight corrections will be made to couple of questions ..

CLASS TEST EXAMINATION – 2013 – 14 (September)

PHYSICS (Theory)

Paper – 1

General Instruction:

 (i) All working including rough work should be done on the same sheet as, and adjacent to the rest of the answer. DO NOT WRITE ON QUESTION PAPERS.

(ii) The intended marks for questions or parts of questions are given in brackets []. (Material to be supplied: Log tables including Trigonometric functions)

(iii) A list of useful physical constants is given at the end of this paper.


PART I (Compulsory)

Q 1:                                                                                                                                                        5 marks

Answer all questions briefly and to the point:

(i). What’s the magnetic flux produced by a long straight wire carrying a current of 1 A, if we are to measure such at a radial distance of 1 meter and through an unit cross section area?

(ii). What’s the force experienced by a 1 meter long wire carrying a current of 1 mA if its aligned with a magnetic field of strength 100 Tesla?

(iii). What’s the speed of an electron if its moving in a magnetic field of 1 Tesla in a circle of radius 100 cm  perpendicular to the field.

(iv). If the flux of a magnetic induction changes at a rate of 10 Weber per second what’s the emf induced by such according to Faraday’s law?

(v). In a mutual induction system the primary coils are less in number than the secondary coils by a factor of 10. If a voltage of 100 Volts is applied in the primary coils what will be the output voltage?





Answer all questions in this part.


  1. A.      An α-particle was targeted into a magnetic field of strength 10-2 Tesla at a speed of 0.4 c. If the particle experiences a force of 100 N, what’s the angle it makes to the field direction?                                                                                                                                                 3 marks.
  2. B.      Elementary particles are known to increase their mass when they travel faster, by a factor of g = [sqrt (1-v2/c2)] -1, that is new mass m = m0g where m0 is the original mass called REST MASS. What’s the mass of the particle at a given speed of 0.5c for the above problem?                            3 marks


  1. A.      What’s the speed of an electron in a cathode ray tube if the electric field and magnetic field are of unit strength in SI unit? Calculate magnetic force experienced by the electron.                                                                                                                                                                     4 marks
  2. B.      Derive the formula for magnetic field produced by an infinitely long straight conductor.                                                                                                                                                 4 marks


  1. A.      A magnetic dipole moment of unit strength is placed in a magnetic field strength B=10-4 Tesla at an angle of 300. What is the magnitude of torque and potential energy of the dipole?                                                                        3 marks
  2. B.      Write the integral form of Ampere’s circuital law in terms of surface element vector ds. Derive the magnetic field produced by a torroid assuming symmetry of the torroid.   3 marks         


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