What is the ideal transformer equation?

Hint: A transformer is an alternating current device that is used to step down or step up voltages. Certain assumptions are made in order to visualise the current flow and other circuit properties of a transformer, and a conceptual circuit is created, which we can refer to as an ideal transformer.

Complete answer:
An ideal transformer is one that does not have any losses such as copper or core. The output power of this transformer is equal to the input power. This transformer's efficiency is 100 percent, which means there is no power loss within the transformer.
The equation is as follows: $\dfrac{{{E_2}}}{{{E_1}}} = \dfrac{{{I_1}}}{{{I_2}}}$

Additional Information:
An ideal transformer operates on two fundamental principles: -
An electric current generates a magnetic field, and a changing magnetic field in a coil induces a voltage across the coil ends. The magnetic flux is created when the current in the primary coil is changed. As a result, changes in the magnetic field can cause a voltage to be generated within the secondary coil.
A magnetic field is created when current flows through the primary coil. Because the two windings are wrapped in the region of a very high magnetic core, such as iron, the magnetic flux is supplied through the two windings. When a load is connected to the secondary coil, the voltage and current will be directed in the indicated direction.

Note:
It should be noted that Transformers are typically very efficient, so this formula of ideal transformer $\dfrac{{{E_2}}}{{{E_1}}} = \dfrac{{{I_1}}}{{{I_2}}}$ , is a good approximation. When the voltage is raised, the current is reduced by the same factor. The square of the turns ratio transforms the impedance in one circuit.