A transformer is used to change the voltage level of an AC current. In this case, the transformer is converting 27 watts of incoming power to 20 volt-amperes (VA) of outgoing power.
A transformer works by using two coils of wire, known as the primary and secondary coils, wrapped around a magnetic core. When an alternating current is passed through the primary coil, it creates a changing magnetic field which induces a current in the secondary coil, resulting in a change in voltage.
The efficiency of a transformer is affected by factors such as the quality of the materials used in its construction, the design and size of the transformer, and the frequency of the AC current. Higher quality materials and a well-designed transformer will result in higher efficiency.
The input power of a transformer is the power that is supplied to the primary coil, while the output power is the power that is delivered from the secondary coil. In this case, the transformer is converting 27 watts of input power to 20 VA of output power.
AC/AC transformers are commonly used in electronic devices to convert the voltage of AC power to a lower or higher level, depending on the needs of the device. They are also used in power distribution systems to step up or step down the voltage for transmission over long distances.