Chapter 19
Magnetism
Honors Physics
Lecture Notes
Tuesday May 8th
Magnetism
2
TODAY’S AGENDA
Tuesday, May 8
 Magnetic Field of a Long Straight Wire
UPCOMING…
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Wed:
Thurs:
Fri:
Mon:
Tues:
Mechanical Universe: Magnetic Fields
Magnetic Fields of Current Loops and Solenoids
AWARDS DAY
Review
TEST 3
3
Magnetism
Sections
Magnetic Field of a Long Straight Wire
Magnetic Force Between Two Parallel Conductors
Magnetic Fields of Current Loops and Solenoids
The Right-Hand Rule
Chapter 19
Magnetic
Field of a CurrentCarrying Wire
Negative Current
Zero Current
Positive Current
Magnetic Force on a Current-Carrying Conductor
A magnet exerts a force on a current-carrying wire. The
direction of the force is given by a right-hand rule.
Magnetic Force on a Current-Carrying Conductor
FM
FM
Magnetic Force on a Current-Carrying Conductor
The force on the wire depends on the current, the length of
the wire, the magnetic field, and its orientation.
F  IL B sin θ
q
L
The force is directed
into the screen.
I
B
This equation defines the magnetic field B.
Unit of B: the tesla, T.
N
1T 1
A m
Magnetic Force on a Current-Carrying Conductor
The force on the wire depends on the current, the length of
the wire, the magnetic field, and its orientation.
F  IL B sin θ
F
When the current is
perpendicular to the
magnetic field.
F  IL B
B
I
L
Magnetic Force on a Current-Carrying Conductor
A 1.5-m length of wire carrying 4.5 A of current is oriented
horizontally. At that point on the Earth’s surface, the dip
angle of the Earth’s magnetic field makes an angle of 38° to
the wire. Estimate the magnitude of the magnetic force on
the wire due to the Earth’s magnetic field of at this point.
B = 5.5 x 10-4 T
F  IL B sin θ
Be
I
F = 2.28 x 10-3 N
q