a technician connects the red lead of a voltmeter to the b+ [output] terminal of an ac generator and the black lead to the battery positive terminal. he starts the engine and turns on all the lights and electrical accessories. what is the technician measuring?

He is testing for voltage drop (voltage drop test)

Explanation:

Connecting the red lead of a voltmeter to the B+ output to an ac generator and black lead to a battery +ve terminal measures the voltage drop in the circuit when the engine is turned ON and all electrical accessories too.

with this he knows if the alternator is charging the battery.

where are the vectors ?