(b) How would you compare the magnetic moments of two magnets? 7. Outline all the steps it would be necessary to take in order to calibrate an ammeter fundamentally. 8. (a) State Laplace's law of magnetic action for an element of current and use it to find the value of the intensity at a point in the field due to an infinitely long wire bearing a current. (b) A current of 5 amperes traverses a coil of wire of mean diameter 40 cm., consisting of 20 turns, placed in a vertical plane at right angles to the magnetic meridian. Compare the times of oscillation of two small magnets of moments M and M' and of equal masses and equal dimensions, placed at the centre of this coil. Horizontal component of earth's magnetic field=0.17. 9. (a) When a rush of electricity due to an induced E.M.F. is sent through a ballistic galvanometer, find an expression for the total quantity which has passed, in terms of the change in the number of lines of induction threading the circuit, and the resistance of the circuit. (b) A long solenoid whose average diameter is 10 cm., and whose length is 200 cm., is wound with 2000 turns of wire and carries a current of 3 amperes. A secondary circuit of 300 turns of resistance 15 ohms is wound over the primary and connected to a ballistic galvanometer whose resistance is 20 ohms. When the primary current is broken find the total quantity of induced electricity in secondary in coulombs. 10. A Leyden jar discharges against self-induction and resistance. Establish the equation of discharge, and then write notes on (1) the nature of the discharge, (2) the generation of electro-magnetic waves. FACULTY OF ARTS. PRELIMINARY HONOUR PHYSICS. Experimental Paper. 1. From the record in your data book, write a full report of your determination of the efficiency of a motor. 2. (a) What do you consider the advantages in representing experimental results, whenever possible, by a graph? (b) What should determine the length chosen to represent unit magnitude on each scale? 3. Give as fully as possible, illustrating by diagrams, the procedure you would follow in calibrating a coil of platinum wire for use as a resistance thermometer in the neighborhood of 40°C. 4. (a) Describe in detail, including instrument adjustments, the spectrometer method of measuring the index of refraction, for yellow (D) light, of a liquid. (b) In a certain determination of the index of a glass prism, the following numbers were obtained: angle of glass prism.... ..58° 48'. angle of minimum deviation...46° 12'. To how many significant figures should your result be given if the instrument reads to 1 minute? (Mathematical tables will be provided on application). 5. Describe a static and a kinetic (vibrational) method of measuring either, (a) Young's modulus, or (b) the coefficient of rigidity, of a steel wire. In what units will your result be expressed? FINAL HONOUR PHYSICS. Optics. Write upon five of the first six equations and then upon number as the equation of a plane wave light disturbance. Show that is a solution of (1), and define the various quantities in this latter expression. 2. Show that the effect of a plane light wave on an exterior point is that of one half the central half wave length zone. 3. Discuss the measurement of wave-length by the Fresnel bi-prism, and set up the laboratory equation. 4. Using the Michelson interferometer, fringes are seen which are approximately circles. Upon what does the position of the centre of the system of circles depend, and how? What is the adjustment in order that the central fringe shall be a straight line? Sketch the principal parts of the interferometer. 5. Discuss the determination of the purity of a sample of sugar by the rotation of the plane of polarization, or discuss the method of analyzing elliptically polarized light which you employed in the laboratory. 6. Deduce Maxwell's equations in the form |