The transformer is an electrical device which is used to step-up or step-down the ac voltages from one level to another. Transformers play important role in our electrical power systems are divided into many types.
As we previously discussed transformers can step-up or step-down the ac voltages. On these basis we have two types. A step-up device converts lower level of voltages to higher level, whereas a step-down converts higher level of voltages to lower level.
A transformer is made of two parts, a central core, and two windings (the primary and secondary). The transformation of voltage depends on the ratio of turns between these windings. If primary turns are Np and secondary turns are Ns, the primary voltage Vp will be related to secondary voltage Vs by the equation:
Np/Ns = Vp/Vs
What is 12-0-12 CT
While purchasing an electrical transformer you might come across the transformer labeled as 12-0-12 CT. The term CT represents center tapped transformer and it has tappings which can be used to achieve two 12 V supplies or a single 24 V supply.
What is VA
A transformer usually mentions the rating in VA. The term VA is related to the power factor of equipment. For small level projects, you can connect a load of approximately 0.7 * VA wattage rating to that. (To understand this watch video).
How to use small transformer in your project
In this electrical engineering video, the practical method of using a transformer at your home is provided. This video first introduces you to the basic concepts of the transformer and its working. Later it explains how to wire it to your outlet (includes Europe and USA configuration).