what are Induced Magnetic Dipole Moments?

what are Induced Magnetic Dipole Moments?


1 Answers

Sachin Tyagi
31 Points
15 years ago

In some materials in which the molecules do not have a permanent electric dipole moment, as we discussed in earlier. An applied electric field can induce a dipole moment by causing a separation of the positive and negative charges in the molecule. A similar effect occurs for magnetic fields, in materials that lack permanent magnetic dipole moments; an applied magnetic field can induce a dipole moment. 


Figure shows:- the double loop has no permanent magnetic dipole moment, but it acquires an induced dipole moment when the magnet approaches the loop.The loop is repelled by the force on the induced moment.

Figure shows how this might occur. Consider a double loop, consisting of two single loops carrying identical currents in opposite directions, in a nonuniform field that might be produced by a permanent magnet. The net magnetic moment of the double loop is zero, because the two single loops have magnetic moments of equal magnitudes but opposite directions. As the magnet is brought closer to the double loop, the flux through the loops increases, causing an induced current that, according to Lenz’s law, must be directed clockwise. This loops, gives a net current I - iind in the upper loop and i + iind in the lower loop. The result is a net induced magnetic moment directed downward. The N and S poles of the equivalent magnet are shown, from which it can be seen that the force on the double loop due to the magnet is repulsive (upward).

We see that (again talking the z axis as positive upward), µz <0 and dBzldz <0, so that Fz >0, corresponding to an upward force, in agreement with the previous conclusion.

In summary, in a nonuniform magnetic field, permanent dipoles are rotated into alignment with the field and attracted to the source of the field, but induced dipoles are repelled from the source of the field.

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