7. A 10 H.P., 200 volt, 2 phase induction motor has a power factor of .85, and an efficiency of .87. It is connected to the alternator by four wires, each having a resistance of 0.1 ohm. Find the cost of the power lost in the line per year (300 days), if power is worth 5 cts. per K.W.-hour and the motor runs 10 hours per day.

8. Why are the larger capacity systems A.C. systems? Describe the ordinary methods of power generation and distribution.

9. A magnetic circuit consists of iron laminations in the form of discs, 9′′ in diameter, with a hole in the centre of 7" diameter. These are built up to a thickness of 3 inches. Find the ampere-turns necessary to wind on the ring so formed in order to produce a flux density of 100,000 lines per sq. in.; permeability of the iron is 500.

FACULTY OF PRACTICAL SCIENCE.

ELECTRICAL ENGINEERING II.

1. State the usual limits of allowable temperature rise in electrical machines and explain fully the methods of obtaining the temperature rise and correcting the observed rise for room temperatures other than standard.

2. Define Hysteresis, Permeability, and Reluctance as applied to the magnetic circuit. Describe briefly one ballistic method of obtaining the Hysteresis Loop for a sample of iron stampings.

3. A magnetic circuit of a certain D.C. generator is made up as follows:

Find the ampere turns necessary to produce a flux of 6,000,000 maxwells through the Air Gaps, Teeth and Armature Core; and a flux of 7,250,000 through the Yoke and Magnet Cores.

4. An induction motor is frequently referred to as an "asynchronous" or "non-synchronous" motor. Explain.

5. Three, 75 K.V.A., 60 cycle, 2200 to 440 volt, single phase transformers are used to connect a 3 phase, 250 H.P., 440 volt induction motor to a 2200 volt, 3 phase system.

Show the necessary transformer connections, and find the current in the H.T. and L.T. coils and the current taken from the 2200 volt mains when the motor is carrying full load, its efficiency being .88 and its power factor .9. Assuming same efficiency and power factor, what load could the motor carry if one transformer was destroyed and the current on the other two was 25% above full load value?

6. Taps are provided on the low tension side of the above transformer so that 40% of normal voltage may be impressed between motor terminals for starting purposes. If the motor at starting takes three times its normal load current, what will be the current at starting taken from the 2200 volt mains. (Express latter as a percentage of the full load line current).

7. Two circuits, one having a resistance of 5 ohms and a reactance of +6 ohms, the other having a resistance of 8 ohms and a reactance of -3 ohms, are connected in parallel. Find the combined impedance of the circuit so formed.

8. A 5 K.W., single phase, 60 cycle, 6600 to 110 volt transformer has a H.T. resistance of 82 ohms and a L.T. resistance of .022 ohm at 50°C. The impedance volts on the H.T. side at 50°C. are 158. The core loss is 50 watts and the low tension leakage current is1.32 amps.

(a) Neglecting the resistance and reactance of the transformer windings, find the total H.T. amperes and the H.T. power factor when the L.T. supplies 5 amps. to a circuit with a power factor of 90%.

(b) Calculate the H.T. voltage if the L.T. is supplying full load current at 110 volts to a circuit having a power factor of 75%.

FACULTY OF PRACTICAL SCIENCE.

ELECTRICAL ENGINEERING III.

1. Define the following: Intermittent current, complex alternating current, harmonics, inductive reactance, condensance, condensive reactance, impedance, oscillation frequency, virtual e.m.f., coefficient of self-induction.

2. Discuss in detail the energy transformations which take place when an oscillation is set up in a circuit.

3. Two alternating e.m.fs., represented by the equations e, 1900 sin 157t,

e, 200 sin(157-30°),

are connected in series. Determine the equation for the resultant.

4. Describe the various systems used for representing alternating e.m.fs. and currents graphically, noting the advantages and disadvantages of each system.

5. The exciting circuit of a generator consists of 8 coils, each having 1000 turns. The poles are 8"x8" and the air gap 14". Neglecting the reluctance of the metallic portion of the magnetic circuit, calculate the inductance of the exciting circuit.

6. A circuit, of which R=5, L= .2, C=25 m.m., is connected to a 440 volt 60 cycle system. Determine (a) the current, (b) the condensance component of the potential, and (c) the power taken by the circuit.

7. Describe the principle (illustrating by sketches) on which the Weston indicating wattmeter is constructed. Show

how it should be connected to a circuit to measure power, and point out the possible errors.

8. Illustrate by diagrams how you would arrange switches and connections to measure power on any 3-wire system, using only one wattmeter. State how the total power is determined from the meter readings.

9. What is meant by electric resonance? What conditions give rise to this phenomenon? Under what conditions is resonance objectionable?