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Magnetism
Whenever electrical current flows, a measurable effect called
magnetism
is produced in
the vicinity of that current. For straight conductors, the magnetic field circles around the
current in a direction dictated by the
RightHand Rule
(
RHR
). There are many versions of
this rule, and the best one for this first
situation is to give the
thumbsup
sign
with the thumb extended in the
direction of the current. The fingers
then wrap in the direction that the
B
field
(magnetic field) lines encircle the
current. In fact, if you place a magnetic
compass near a wire, it will align with B.
The magnitude for such a current is given by
Ampère’s Law
, the magneticfield
equivalent of Gauss’s Law for electric fields. The equation is
B=
µ
₀
I
in
/
l
where
B
is the
magnetic field density measured in
teslas
(
T
),
µ
(“munought) is a constant called the
permeability of free space
(
4
π
×
10
⁻⁷
),
I
in
refers to the current within the
Amperian
surface
(which is just a circular loop this time), and
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This note was uploaded on 04/05/2012 for the course PHYS 131 taught by Professor Tibbets during the Spring '11 term at Cuyamaca College.
 Spring '11
 Tibbets
 Current, Magnetism

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