A group of students while coming from the school noticed a box marked “Danger H.T. 2200 V” at a substation in the main street. They did not understand the utility of a such a high voltage, while they argued, the supply was only 220 V. They asked their teacher this question the next day. The teacher thought it to be an important question and therefore explained to the whole class.
Answer the following questions :
(i) What device is used to bring the high voltage down to low voltage of a.c. current and what is the
principle of its working?
(ii) Is it possible to use this device for bringing down the high dc voltage to the low voltage? Explain.
(iii) Write the values displayed by the students and the teacher.
Answers
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1) Transformers are devices used in
electrical circuits to change the voltage of electricity flowing in the circuit.
Transformers can be used either to
increase the voltage (called "stepping up") or decrease the voltage ("step down"). This happens to electricity during the journey from a power plant to your home.
2) When a d.c voltage source is applied
across the primary of the transformer,the current in the primary coil remains constant. Hence there is no change in the magnetic flux linked with the secondary. Therefore the voltage across the secondary coil is zero.Thus transformer can't step up dc voltage.
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