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