UCSB Science Line
Sponge Spicules Nerve Cells Galaxy Abalone Shell Nickel Succinate X-ray Lens Lupine
UCSB Science Line
How it Works
Ask a Question
Search Topics
Our Scientists
Science Links
Contact Information
I have a very simple question, why does an induced coil always produce AC current in a generator regardless of the orientation of the magnets? I always thought the change in the direction of current was caused by the shift in the magnetic field caused by the rotation of the magnets North and South poles, but that is not the case; my question is why does the current reverse when the field change?
Question Date: 2018-06-14
Answer 1:

In many cases (generators), AC current is produced by rotating magnets around a coil. As the poles of the magnets change, the direction of the magnetic field changes, and the direction of the current produced in the coil also changes. The direction of the current changes because the direction of the magnetic flux relative to the plane of the coils changes. In other words, there is a directionality to the orientation of the two poles of the magnet such that "north-to-south" does NOT equal "south-to-north".

The magnitude of the flux (how much magnetic field goes through a plan perpendicular to it) would be the same (for example, 2 teslas), but the direction is not the same. The concept is analogous to the positive and negative sides of a number line, and we call such quantities "vectors" - quantities that must be specified in terms of both magnitude AND direction. Because the direction of the magnetic field changes, the resulting direction of the current also changes. To make this a little clearer, it would not matter whether the north pole of the magnet starts on the left or right side of the coil of wires. The rotation of the magnet would still produce alternating currents.

For more information and some helpful graphics, you may want to visit this website: read here .

Answer 2:

It is because a static magnetic field generated by the inductor coil does not create a voltage in the target coil. By flipping the current in the inductor coil on and off, you create alternating voltages in the target coil by virtue of the magnetic field appearing and disappearing, i.e. current on, magnetic field on, creates voltage in direction of magnetic field; current off, magnetic field off, creates voltage opposite the direction of formerly existing magnetic field.

Click Here to return to the search form.

University of California, Santa Barbara Materials Research Laboratory National Science Foundation
This program is co-sponsored by the National Science Foundation and UCSB School-University Partnerships
Copyright © 2020 The Regents of the University of California,
All Rights Reserved.
UCSB Terms of Use