Calendar: 1898-1899 Page 771

FACULTY OF SCIENCE cxxxix In what way does the current in the armature of direct current motors and generators disturb the induction density over the bored pole face What effect has it upon the electromotive force of the armature in the case of motors and generators with constant excitation due to the magnet eoils State the causes for the dissipation of energy in an alternate current transformer when in action with no current in its secondary circuit How would you expect this dis- sipation of energy to vary with variation of frequency and applied potential difference Why is it in dynamo electric machines capable of dealing with exceptionally great power that special precautions have to be resorted to in order that the temperature may not be excessive How is this generally dealt with in practice In two and three phase generators you have given the potential differences between the ends of the respective circuits and this is assumed constant Show in the two cases how the potentials between and the currents in the line wires are affected when the mesh and star groupings of conductors are adopted XIX Pledjamcal £nguuertng THIRD YEAR Not more than questions to be attempted One cubic foot of air is admitted into cylinder at temperature of 200 and atmospheric pressure it is heated to temperature of 1000 its volume being kept constant and it is then made to expand at constant pressure until its volume is doubled Draw diagram on pressure-volume base for these opera- tions marking the pressure and temperature at each point and noting the units of heat added during each process Explain shortly the difference between adiabatic iso- thermal and constant pressure expansion for perfect gas Draw an approximate diagram for each taking lb of air as your basis showing the curves in their correct relative position