Question

While coming from school, few students noticed a box at roadside marked "Danger H.T 200 V " which is located inside a substation on the main street. These students did not understand the utility of such high voltage box inside a substation as they know that the supply they used to receive were only 220 V, so they all happen to argued with each other. Next morning in the school, these students asked about it from. their teacher. The teacher visualized that it is an important question and hence everybody in the class should this. 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 d.c. voltage to the low voltage ? Explain. 

(iii) Write the values displayed by the students and the teacher.

Answer 1

Transformer :

Working principle : Mutual induction

Whenever an alternative voltage is applied in the primary windings, an emf is induced in the secondary windings.

(ii) No, there is no induced emf for a dc voltage in the primary.

(iii) Inquisitive nature / Scientific temperament .

Concern for student / helpfulness / professional honesty.