Explanation
Transformer work on ac only.
According to Lenz's law.
Effective length between A and B remains zero.
Circular loop behaves as a magnetic dipole whose one surface will be N-pole and another will be S-pole. Therefore magnetic lines a force emerges from N will meet at S. I Hence total magnetic flux through x – y plane is zero.
If the current increases with time in loop A, then magnetic flux in B will increase. According to Lenz’s law, loop – B is repelled by loop – A.
The mutual inductance between two coils depends on their degree of flux linkage, I. e., the fraction of flux linked with one coil which is also linked to the other coil. Here, the two coils in arrangement (a) are placed with their planes parallel. This will allow maximum flux linkage.
Both AD and BC arc straight conductors moving in a uniform magnetic field and e.m.f. will be induced in both. This will cause electric fields in both, but no net current flows in the circuit.
When key k is pressed, current through the electromagnet start increasing, 1. e., flux linked with ring increases which produces repulsion effect.
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