This connection is not allowed. Check the multimeter's reading. Check the other side Complete the testing. Check the circuit again. Ohh Wrong answer ! Thats correct answer Side A is the primary side with two coils a1a2 and a3a4. Side B is the secondary side with single coil b1b4 and tappings b2 at 86% and b3 at 50% of the coil. 1. When power supply is connected across the primry coils a1a2 and a3a4 themselves connected in parallel, the voltage per turn at the primary side remains same as compared to when power supply is connected to a simplle coil a1a2. 2. Since there are twice the number of turns in the secondary side, then the induced voltage is twice that of the voltage across the primary. When the two coils a1a2 and a3a4 are connected in series with correct polarity, then there is an addition voltage. However for incorrect polarity, the resultant voltage has to be computed by subtracting one from another. When connected as an autotransformer, we can obtain several different values of voltage across different combination of coil terminals. However, ensure that the current flowing through the coil, or the voltage then do not exceed the rated values(as mentioned in the nameplate) under any condition.