Two coils are wound on the iron core. The magnetic flux generated by each coil does not leave the core and is divided equally in its branches. When coil 1 is connected to an AC circuit with a voltage of 40 V, the voltage across coil 2 is 10 V. What is the voltage at the open terminals of coil 1 if coil 2 is connected to an AC circuit with a voltage of 10 V?
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