You have a bar magnet anda circular conducting loop, and you wish to induce a current in the loop that changes direction regularly: clockwise, counterclockwise, clockwise, and so on. Explain how to do this while the loop remains at rest on a wooden table.

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canhaulatlt · Accepted Answer

The bar magnet generates a dipole-like magnetic field, with closed field lines that leave the north, circle around, and enter into the south.To induce a periodic current in the loop that is resting in the table, we can move the vertically oriented bar in a vertically periodic motion in the loop&#039;s symmetry axis.To understand this, let us look more carefully into the problem. Suppose we are approaching the bar, from above, with the north pole headed down. With the north approaching, the magnetic field lines in the position of the loop are crossing it downwards. And this field is increasing, since the bar magnet is approaching. Also, at every element of the loop, we visualize that the magnetic field vector can be decomposed into two components: one that points downwards and another that points radially away from the symmetry axis.Now, if we instea view the problem in t bar&#039;s reference frame, the loop is approaching the bar&#039;s north pole. In that case, any free positive charges q that are at any element of the approaching loop will feel a magnetic force given by   q      v    →    ×      B    →  .Thus, the field lines of the magnetic force field generated in the loop are circles with counterclockwise orientation when viewed from above the loop.Consequently, we clearly see that these magnetic force field lines seen by the bar magnet are actually electric force field lines when seen by the loop. As a result, the electric field lines are circles with counterclockwise orientation when viewed from above the loop. In both &quot;views, the effect is the induction of a counterclockwise current in the loop.When, on the other hand, the bar is moving away from the loop, the velocity vector changes its sign. Thus, the magnetic force field in the bar&#039;s reference frame or the electric force force field in the loop&#039;s reference frame also change signs. As a result, in both &quot;views&quot;, the effect is the induction of a clockwise current in the loop.

You have a bar magnet anda circular conducting loop, and you wish to induce a current in the loop that changes direction regularly: clockwise, counterclockwise, clockwise, and so on. Explain how to do this while the loop remains at rest on a wooden table.

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