Is a Choke a Transformer?

A "choke" is the common name given to an inductor that is used as a power supply filter element. They are typically gapped iron core units, similar in appearance to a small transformer, but with only two leads exiting the housing.

Is choke the same as transformer?

The difference is basically in usage. A choke uses the inductance as a primary characteristic to affect a signal. In a transformer the inductance is secondary and is just to establish the magnetizing current with the transformer's primary purpose being to transform one signal level (or impedance) to another.

Can a transformer be used as a choke?

Yes. A transformer is made of (at least) two windings that are coupled together through a ferromagnetic core (iron plates). A choke/inductor uses exactly the same principle, but only has (usually) one winding. Both transformers and inductors need not to have a core - may be simply a set of wire loops (aircore).