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Lecture 23—Faraday’s Law
Electromagnetic Induction AND Review of Right Hand Rules
Monday, March 30
Electric Currents Also Create Magnetic Fields
A long, straight wire
A current loop A solenoid
Slide 24-15
The Magnetic Field of a Straight Current-Carrying Wire
Slide 24-16
Drawing Field Vectors and Field Lines of a Current-Carrying Wire
Slide 24-21
The Magnetic Field of a Solenoid
A short solenoid A long solenoid
Slide 24-24
Example
What is the direction and magnitude of the magnetic field at point P, at the center of the loop?
Slide 24-30
The Force on a Charged Particle Moving in a Magnetic Field
Slide 24-32
sinF qvB
Magnetic Fields Exert Forces on Currents
Fwire ILBMagnitude of the force on a current segment of length L perpendicular to a magnetic field
Slide 24-37
The Torque on a Dipole in a Magnetic Field
IA B sin
Slide 24-43
• Electromagnetic induction
• Lenz’s law
• Faraday’s law
• The nature of electromagnetic waves
• The spectrum of electromagnetic waves
Electromagnetic Induction and Electromagnetic Waves
Topics:
Sample question:The ultraviolet view of the flowers on the right shows markings that cannot be seen in the visible region of the spectrum. Whose eyes are these markings intended for?
Slide 25-1
Electromagnetic Induction
Slide 25-8
Change magnetic field through coil, change the area of the coil, or change the angle coil makes with respect to the magnetic field.
Motional emf
vlB
Slide 25-9
Magnetic Flux
Slide 25-10
Lenz’s Law
Slide 25-13
Lenz’s law There is an induced current in a closed, conducting loop if and only if the magnetic flux through the loop is changing. The direction of the induced current is such that the induced magnetic field opposes the change in the flux.
Homework due Wednesday
• Read: 23: 1-3 Faraday’s Law and electromagnetic induction
• Problems: 25: 1, 2, 4• 38: torque on current loop• 39: ditto• WB 24: 23-30 forces on straight wires and torques on
loops
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