(i) The device that is used to bring high voltage down to low voltage of an A.C. current is a transformer. It works on the principle of mutual induction of two windings or circuits. When current in one circuit changes, e.m.f is induced in the neighboring circuit.
(ii) The transformer cannot convert D.C. voltages because it works on the principle of mutual induction. When the current linked with the primary coil changes the magnetic flux linked with the secondary coil also changes. This change in flux induces E.m.f in the secondary coil. If we apply a direct current to the primary coil the current will remain constant. Thus, there is no mutual induction and hence no e.m.f is induced.
(iii) The value of gaining knowledge and curiosity about learning new things is being displayed by the students. The value of providing good education and undertaking the doubts of students has been displayed by the teacher.
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