Question

does lenz's law violate the principle of conversation of energy

Answer 1

Lenz's law upholds the general principle of the conservation of energy. If the current were induced in the opposite direction, its action would spontaneously draw the bar magnet into the coil in addition to the heating effect, which would violate conservation of energy.

Answer 2

No. Consider the example of dropping a magnet down a copper pipe. As the magnet falls, it gives up some of its kinetic energy to the pipe as the electric current flowing through the pipe. Meanwhile, its potential energy from gravity is being converted to kinetic energy as it falls. This means that overall, the process is:

Gravitational potential energy → kinetic falling energy → electric energy → thermal energy → electromagnetic energy (radiated heat).