~Ques. What is the function of the motor?~
Ans. Since the motor runs at a speed proportional to the energy passing through the circuit, it drives the counting mechanism at the proper speed to indicate the amount of energy consumed.
~Ques. What is the object of the generator?~
Ans. It furnishes a suitable counter torque or load for the motor.
[Illustration: FIG. 2,530.--Westinghouse polyphase induction type watt hour meter, covers removed. This type is made for two phase three wire and four wire, and three phase three wire and four wire circuits. Meters for circuits of more than 300 amperes or 500 volts require transformers, but, like the self-contained meters, are calibrated to read directly in kilowatt hours on the dial, without a multiplying constant.]
~Ques. Is there any other resistance to be overcome by the motor?~
Ans. It must overcome the friction of all the moving parts.
[Illustration: FIGS. 2,531 to 2,533.--Diagram of electromagnetic circuit of Westinghouse induction type watt hour meter, and diagram showing rotation of field. The dotted lines show the main paths of the magnetic flux produced by the two windings, the directions, however, are constantly reversing owing to the alternations of the current in the coils. Denoting the shunt and series pole tips by the letters as shown, a clear statement of the relation of the fields for each quarter period may be given. The signs + and - represent the instantaneous values of the poles indicated. Thus, ~at one instant~ the shunt pole tips A, C, and A₁ are maximum +, -, and +, respectively because the instantaneous value of the current is maximum, while the value of the series flux is zero. ~At ¼ period later~ the shunt current is zero, giving zero magnetic pressure at the pole tips, while the series current has reached a maximum value, giving maximum-and + at the pole tips B and D. ~At the next ¼~ ~period~ the shunt current is again maximum, but in a direction opposite to what it was at the beginning, making the pole tips A, C, and A₁ +, -, and +, respectively, while the series current again is zero, etc., the values for the complete cycle being given in fig. 2,533. It will be observed from the table that both the + and - signs move constantly in the direction from A₁ to A, indicating a shifting of the field in this direction, the process being repeated during each cycle.]