sTEm-at-Work Puzzle #49: Wind Turbine Final Quality Assurance Test

A technician working at a small wind turbine manufacturing company is performing the last of many, final quality assurance checks on a system to be shipped. The test requires that the voltage signal and the current signal be checked. When the system is operating correctly, the two signals are not in phase. (The voltage and current do not increase and decrease at the same time.) The technician expects the voltage to go down after the current goes down. That is (for the system being tested) the voltage “lags” the current. The technician uses a two channel oscilloscope to track the voltage and current signals at the same time. This measurement tool has beams (two dots on the screen) that sweep from left to right as they trace the two signals onto the screen at the same time.

In the oscilloscope cartoon below, the turbine's voltage signal is connected to Channel B and its current signal is connected to Channel A. The technician has the wind turbine shipped to the customer. (Yes or No). Submit your answer below this blog post, or at

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