Question

Assertion : We use a thick wire in the secondary of a step down transformer to reduce the production heat.
Reason : When the plane of the armature is parallel to the line of force of magnetic field, the magnitude of induced e.m.f. is maximum.

• A. If both the assertion and reason are true and reason is a correct explanation of the assertion
• B. If both assertion and reason are true but assertion is not a correct explanation of the assertion
• C. If the assertion is true but the reason is false
• D. If both assertion and reason are false

Answer 1

Answer: (B)

A step-down transformer converts electrical energy from a high voltage to one at a low voltage. Accordingly the current in the secondary will be larger than that in the primary. In order to produce less heat in the secondary, we use a wire of lesser resistance i.e. thick wire. We also know that when the plane of the armature is parallel to the lines of force of magnetic field, the rate of change of magnetic flux linked with it is maximum. Therefore the e.m.f. induced in the armature in this orientation is maximum.