CBSE-XI-Physics
39: Alternating Current
- #11A transformer is designed to convert an AC voltage of 220 V to an AC voltage of 12 V. If the input terminals are connected to a DC voltage of 220 V, the transformer usually burns. Explain.Ans : A transformer is ideally an inductive coil. For an inductor connected across a DC voltage,
`` V-L\frac{di}{dt}=0``
`` \Rightarrow V=L\frac{di}{dt}``
`` \Rightarrow \int di=\frac{V}{L}\int dt``
`` \Rightarrow i=\frac{Vt}{L}``
For a DC source, the current across the inductor will increase with time and can reach a very large value, which can burn the transformer.
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