Transcript Magnetism

Chapter 19
Magnetism
Honors Physics
Lecture Notes
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Thursday May 10th
Magnetism
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TODAY’S AGENDA
Thursday, May 10
 Magnetic Fields of Current Loops and Solenoids
UPCOMING…
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Fri:
Mon:
Tues:
Wed:
AWARDS DAY
Review
TEST 3
Lab due
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Magnetism
Sections
Magnetic Fields of Current Loops and Solenoids
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Motion of a Charged Particle in a Magnetic Field
If a charged particle is
moving perpendicular to a
uniform magnetic field, its
path will be a circle.
v
q
F
F  q vB
mv 2
qvB 
r
q rB  m v
B
Momentum
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Motion of a Charged Particle in a Magnetic Field
What is the velocity of a beam of electrons
that go undeflected when passing through
perpendicular electric and magnetic fields of
magnitude 8.8 x 103 V/m and 3.5 x 10-3 T,
respectively? What is the radius of the electron orbit if
the electric field is turned off?
me = 9.1 x 10-31kg
qe = 1.6 x 10-19C
v
undeflected means B and E are equal and opposite
F = Eq
F = qvB
mv2/r = qvB
Eq = qvB
r = mv/qB
E/B = v
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Magnetism
The diagram below shows an electron, e, located in a
magnetic field. There is no magnetic force on the
electron when it moves
(A) toward the right side of the screen
(B) toward the top of the screen
(C) into the screen
(D) out of the screen
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Magnetism
A vertical wire carries a current straight down. To
the east of this wire, the magnetic field points
(A) north.
(B) east.
(C) south.
(D) down.
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Magnetic Fields of Current Loops and Solenoids
The direction of the field is given by a right-hand rule.
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Magnetic Fields of Current Loops and Solenoids
A solenoid is a long coil of wire. If it is tightly wrapped, the
magnetic field in its interior is almost uniform:
I
I
N
B
L
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Magnetism
The diagram below shows an
electromagnet made from a nail, a
coil of insulated wire, and a battery.
The south pole of the electromagnet
is located closest to point
(A) A
(B) B
(C) C
(D) D
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