My textbook says that when primary winding of an ideal Transformer is connected to an alternating voltage, an alternating current flows which in turn produces an alternating flux which causes an EMF to be induced in the primary coil which is equal and opposite to the applied voltage. Now how can current flow, if the applied EMF and the back EMF generated in the primary coil are equal? Also if we take an ideal Transformer, the resistance of the windings will be zero and if it is zero then the current in windings will become infinite which is something I am not able to grasp, please explain in detail. Thanks in advance.

  • $\begingroup$ Newton's 3rd law says that there is an equal reaction force to any force but that does not mean that a force cannot accelerate a body. $\endgroup$ – hyportnex Nov 9 '16 at 17:31

An ideal transformer, as the name implies, is not a real object. Thus, in an ideal transformer there are no windings, no core, nothing.

An ideal transformer is an element which is indirectly defined only through the constitutive equations

$$\begin{align}v_2 &= \frac{1}{n}v_1, \\ i_2 &= -ni_1, \end{align}$$

where the reference directions of voltages and currents are chosen according to the convention of multiport devices.

And because of this, the ideal transformer works also in DC!

That said, an ideal transformer can be seen as a limiting case of a pair of lossless coupled inductors with a coupling coefficient of 1 when the primary inductance goes to infinity. In this limit, the current in the primary winding tends to zero when the primary inductance tends to infinity, if the secondary winding is not loaded.

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