l19 ch30 inductors - uml.edu
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Department of Physics and Applied PhysicsPHYS.1440 Lecture19 A.Danylov
Lecture 19
Chapter 30
Inductors
Physics II
Course website:http://faculty.uml.edu/Andriy_Danylov/Teaching/PhysicsII
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Department of Physics and Applied PhysicsPHYS.1440 Lecture19 A.Danylov
Today we are going to discuss:
Chapter 30:
Section 30.8
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Department of Physics and Applied PhysicsPHYS.1440 Lecture19 A.Danylov
InductorsInductors (solenoids) store potential energy in
a form of a magnetic field.
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Department of Physics and Applied PhysicsPHYS.1440 Lecture19 A.Danylov
Inductance (definition)Consider a solenoid of N turns with current I.
The total magnetic flux is I
Φ ~
The coefficient of proportionality is called inductance, L
The SI unit of inductance is the henry, defined as:1 henry = 1 H = 1 Wb/A = 1 T m2/A
The circuit symbol for an ideal inductor is .
The solenoid’s magnetic field passes through the coils, establishing a flux.
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Department of Physics and Applied PhysicsPHYS.1440 Lecture19 A.Danylov
Let’s find solenoid inductanceConsider a solenoid of N turns with current I.
Recall (Lecture 14)
Φ
You see, solenoid inductance depends only on its geometry
Φ Φ ∙ ∥
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Department of Physics and Applied PhysicsPHYS.1440 Lecture19 A.Danylov
Potential Difference across an Inductor
Φ
Δ
Potential difference across an inductor
Note The magnitude of I has no effect on ΔV, only the rate of change of I counts.
If current increases, 0 Δ 0
If current decreases, 0 Δ 0
If current is constant, I=const Δ 0
The induced V decreases if the current is increasing
_
The induced V increases if the current is decreasing+_
Δ
initial final
initial final
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Department of Physics and Applied PhysicsPHYS.1440 Lecture19 A.Danylov
=ΔV across a solenoid when the current increase
(increases)
Magnetic filed created by I
Induced Magnetic filed
I
is in the opposite direction to a direction of I
+ _
(Physics)
" “which can create this induced current
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A. Current I1
B. Current I2
C. They are changing at the same rate
D. Not enough information to tell
Which current is changing more rapidly?
ConcepTest Inductor
41
22
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Department of Physics and Applied PhysicsPHYS.1440 Lecture19 A.Danylov
Thank youSee you next time