The Formal Explanation (and hard way)!
The induced magnetic flux sets up by the induced
current which will be such that it always OPPOSES the
CHANGE of the external flux.!
Lenz’s Law!
You can use the right thumb rule to determine the
direction the current will do that.!
1.!
3.!
The Formal Explanation (and hard way)!
If there is an externally produced magnetic flux through
a coil (i.e., if there is a magnetic field produced by an
outside source that permeates the coil), and if that flux
CHANGES, then:!
The changing external magnetic flux will induce a
current in the coil;!
Example: Assume the
magnetic field diminishes.
In what direction will the
induced current in the
coil flow?!
The induced current will set up an induced magnetic
flux of its own through the coil;!
2.!
4.!
The Easy Way!
Example: Assume the
magnetic field diminishes.
In what direction will the
induced current in the
coil flow?!
1.) Identify the direction of the external magnetic field.!
2.) Identify whether the external magnetic flux is
increasing or decreasing.!
3a.) If the flux is increasing, the coil’s induced current will
set up a magnetic field through the coil that is OPPOSITE
the direction of the external B field.!
5.!
The Easy Way!
3b.) If the flux is decreasing, the coil’s induced current will
set up a magnetic field through the coil that is IN THE
SAME DIRECTION AS the direction of the external
magnetic field.!
4.) If you know the direction of the induced magnetic
field, you can use the right thumb rule to determine the
direction of the current required to produce that field.!
6.!
Following the steps: (1) The
direction of the external B-field is
into the page. (2) The magnetic
flux is decreasing. (3) With the
decreasing flux, the induced B-field
must by WITH the external B-field.
(4) Using the floppy-hand
technique, the current has to be
clockwise to effect that induced
magnetic field. !
7.!