A transformer changes voltage, for more efficient transfer over long distances, or for less voltage from mains supply into a 130v Laptop or equivalent.
Variable transformer may also refer as auto transformer. We can vary the output voltage of the transformer. But in the ordinary transformers output voltage is already designed.
An audio frequency transformer is a transformer designed to operate in the range of frequencies audible to the average human. This range is generally accepted to be from 20 Hz to 20,000 Hz. The usual purpose of an audio transformer is to match impedances between circuit sections. For example: between a microphone and the input of an amplifier, (input transformer), or between the output of an amplifier and the loud speaker. (output transformer).
There need not be any relationship.
A transformer is connected to the output of inverter in order to step up the AC voltage output.
An ordinary transformer has two input/output terminals but a center tapped transformer has 2 input and 3 output terminals. One is taken from the center for a ground connection. This causes it to get 50% of the actual value. And ordinary transformer contains 2 windings. An autotransformer has one.
Your question is incomplete -- what about the transformer?
A variable transformer is capable of changing its output voltage from 0 to maximum output or over a specific range. It is also named an adjustable transformer.
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What is the relation ship between total fixed cost and output?
A function.
A: Transformer by itself goes not alter the phases the output can be in phase or out of phase depending how you look at it.
The coupling between windings will be nearly zero, resulting in nearly zero output. In short, your transformer's not going to work.