How to determine the number of turns in a transformer coil if you have an AC source, a lot of insulated wire, and an AC voltmeter?

Make a coil from insulated wire, connect it with a core With one coil of the transformer, power it from a current source. Using a voltmeter, measure the voltage at the input and output v1 / v2 = n1 / n2, n2 = v2n1 / v2
Then count the number of turns in the second unknown coil.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.