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.

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**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?

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**PART II**

**Answer all questions in this part. **

** Q2: **

**A.**An**α-particle**was targeted into a magnetic field of**strength 10**at a speed of^{-2}Tesla**0.4 c**. If the particle experiences a force of 100 N, what’s the angle it makes to the field direction?**3 marks.****B.**Elementary particles are known to increase their mass when they travel faster, by a factor of g = [sqrt (1-v^{2}/c^{2})]^{-1}, that is new mass m = m_{0}g where m_{0}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**

**Q3: **

**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****B.**Derive the formula for magnetic field produced by an infinitely long straight conductor.**4 marks**

**Q4: **

**A.**A magnetic dipole moment of unit strength is placed in a magnetic field strength B=10^{-4}Tesla at an angle of 30^{0}. What is the magnitude of torque and potential energy of the dipole?**3 marks****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**