U1 / U2 = N1 / N2 in the transformer. If the coil resistance is considered, what do U1 and U2 represent respectively? Is it the voltage at both ends of the coil or the voltage after removing the electromotive force consumed by the resistance? U1 got it. What about U2?

The latter
EMF is divided into two parts, one is consumed by coil resistance
The other part is the voltage applied to the coil, which is counteracted by the induced electromotive force and applied to the secondary coil through the transformer device

For an ideal transformer, the turns of primary and secondary coils are N1 and N2 respectively, and the input and output voltages are U1 and U2 respectively during normal operation. If N1 > N2, please ask:
Please judge the relationship between U1 and U2. Why?
A:U1>U2
B:U1

A: U1 > U2 N1 vs N2 = U1 vs U2

The ratio of voltage between primary coil and secondary coil of transformer is U1 / U2 = N1 / N2. How does this formula come from

When the secondary coil is no-load, the magnetic field in the transformer is generated by the external power supply voltage U1. Specifically, U1 generates no-load exciting current I0, thus generating magnetic potential i0n1, that is, generating magnetic field strength h. No matter whether there is a core or not, the magnetic induction strength (flux density) B, the main flux Φ = BS and the flux linkage ψ 1 = N1 Φ in the original coil are generated in the magnetic circuit, Therefore, the above physical quantities are alternating. According to the law of electromagnetic induction, induced potentials E1 and E2 are generated in the primary and secondary coils, which are also alternating, and the voltage is increased or decreased according to the number of turns. E1 / E2 = N1 / N2 (at this time, the potential E2 in the secondary coil is its terminal voltage U2, U2 = E2), and they are in phase, that is, their instantaneous values increase and decrease at the same time
Moreover, the current I0 in the original coil will produce voltage drops i0r1 and I0 × 2 π FL1 in its resistance R1 and leakage inductance L1 (F: the AC frequency of the power supply), so the sum of these voltage drops and the induced potential in the original coil is balanced with the applied voltage. Because I0, R1 and L1 are very small, the approximate induced potential E1 is balanced with the applied voltage U1 (its value is equal but reversed), U1 ≈ E1 (regardless of phase), So U1 / U2 = E1 / E2 = N1 / N2
Strictly speaking, this is accurate for ideal transformer (no loss, no resistance, no leakage inductance in coil), especially under load

U1 / U2 = N1 / N2 in the transformer. If the coil resistance is considered, what do U1 and U2 represent respectively? Is it the voltage at both ends of the coil or the voltage after removing the electromotive force consumed by the resistance? U1 got it. What about U2?