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Transformer

A group of st...

Question

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.
(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 used 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

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Solution

(i) A step down transformer is used to bring the high voltage down to low voltage of an a.c. current and it is based on the principle of mutual inductance .
(ii) A transformer cannot be used for a dc voltage , because if we use dc voltage it will not change the flux linked with secondary coil and voltage will not be induced in the secondary coil .
(iii) Value displayed by the students = (2200V) voltage across primary coil
Value displayed by the teacher = (220V) voltage across secondary coil .

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Q. A group of students while coming from 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.

Q. The teachers of Geeta's school took the students on a study trip to a power generating station, located nearly 200 km away from the city. The teacher explained that electrical energy is transmitted over such a long distance to their city, in the form of, alternating current (ac) raised to a high voltage. At the receiving end in the city, the voltage is reduced to operate the devices. As a result, the power loss is reduced. Geeta listened to the teacher and asked questions about how the ac is converted to a higher or lower voltage.
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Q. Ram is a student of class X in a village school. His uncle gifted him a bicycle with a dynamo fitted in it. He was very excited to get it. While cycling during night, he could light the bulb and see the objects on the road. He however, did not know how this device works. He asked this question to his teacher. The teacher considered it an opportunity to explain the working to the whole class. Answer the following questions :

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How do they keep high voltage and low current in step down transformers even though Voltage is directly proportional to Current?

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