Final answer:
The input power, P, for the 3-phase star-connected load is the sum of the two wattmeter readings, which equals 4200 W + 1400 W, resulting in a total of 5600 W.
Step-by-step explanation:
The input power of a 3-phase star-connected load can be calculated by summing the readings of the two wattmeters. Thus, the total input power, P, is the addition of the power indicated by the first wattmeter (P1) and the second wattmeter (P2). The calculation becomes P = P1 + P2 = 4200 W + 1400 W = 5600 W.
In electrical engineering, power measurement in three-phase systems can be conducted using two wattmeters, and the total power is the sum of the two readings. This also aligns with the principle that the power output of the source must be equal to the total power dissipated by the load(s), which is a reflection of the conservation of energy.