Dot convention meaning

I have two questions about dot convention for the ideal transformer. I have understood how to use them in writing the voltage drops on the coils, but I have some doubts:

1) Which is the physical cause of their necessity? Intuitively, I think it is due to the fact that the direction of the magnetic field generated by a coil connected to a voltage source depends not only on how it is connected to it, but also on its winding sense.

2) If we write the ideal transformer equation: V2/V1 = I1/I2, do we apply the dot convention as we do for evaluating the voltage drops on the coils?

If it is true, we would write for instance:

V2/V1 = - I1 / I2

for the following scheme, since I1 flows in the dot and then in the inductor, and I2 the opposite. • What did your google search reveal? – winny Jun 24 at 15:26
• When the voltage at the primary dot is on it's positive half-cycle, so is the voltage at the secondary dot. Alternatively, when primary current is flowing in towards the dot (ie a sink), secondary current is flowing out from the dot (ie a source). – Chu Jun 24 at 16:32