1. If two alternating pressures which agree in phase are connected together in series, the voltage at the free terminals of the circuit will be equal to their arithmetical sum, as in the case of direct currents.
Fig. 2,123.—Vectors. A vector is defined as: a line, conceived to have both a fixed length and a fixed direction in space, but no fixed position. Thus A and B are lines, each having a fixed length, but no fixed direction. By adding an arrow head the direction is fixed and the line becomes a vector, as for example vector C. The fixed length is usually taken to represent a definite force, thus the fixed length of vector C is 4.7 which may be used to represent 4.7 lbs., 4.7 tons, etc., as may be arbitrarily assumed.
When there is phase difference between the two alternating pressures, connected in series, the following relation holds:
2. The value of the terminal voltage will differ from their arithmetical sum, depending on the amount of their phase difference.
When there is phase difference, the value of the resultant is conveniently obtained as explained below.
Ques. How are vector diagrams constructed for obtaining resultant electric pressure?
Ans. On the principle of the parallelogram of forces.
Ques. What is understood by the parallelogram of forces?