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# Magnetism AP

Giancoli, Chapter 20: AP Physics Magnetism

Chap 20 Magnetism PPT Giancoli

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20.1: Magnets and Magnetic Fields

What is a magnet? What is a magnetic field? What is a magnetic field line?

20.2: Electric Currents Produce Magnetic Fields

Ørsted’s law {aka Oersted’s} is the law that a steady electric current creates a magnetic field around it.

This was discovered on April 21, 1820 by Danish physicist Hans Christian Ørsted (1777-1851) when he noticed that the needle of a compass, next to a current-carrying wire, turned so that the needle was perpendicular to the wire. Ørsted investigated and found the law which governs how strong the field was. This was the first connection found between electricity and magnetism. The next link found was Faraday’s law of induction. these two laws became part of the equations that govern electromagnetism, Maxwell’s equations. {adapted, Wikipedia}

20.3: Force on an Electric Current in a Magnetic Field; Definition of B

Giancoli Physics

20.4: Force on an Electric Charge Moving in a Magnetic Field

20.5: Magnetic Field Due to a Long Straight Wire

20.6: Force between Two Parallel Wires

20.7: Solenoids and Electromagnets

20.8: Ampère’s Law

20.9: Torque on a Current Loop; Magnetic Moment

20.10: Applications: Motors, Loudspeakers, Galvanometers

20.11: Mass Spectrometer

20.12: Ferromagnetism: Domains and Hysteresis

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Why do magnetic fields have the symbol B? The origin of B was James Clerk Maxwell himself.

See the article by Ralph Baierlein in the American Journal of Physics, v68, n8 (Aug 2000), p.691. In “A Treatise on Electricity and Magnetism“ Maxwell presents a list of the vector quantities he will be dealing with. He then labels them in alphabetical order.

• Electromagnetic momentum at a point: A (now called vector potential)
• Magnetic induction: B (usually called magnetic field)
• Total electric current: C
• Electric displacement: D
• Electromotive force: E
• Mechanical force: F
• Velocity at a point: G
• Magnetic force: H (usually called magnetic intensity)

The use of A, B, D, F, and H has lived on, but C and G have been abandoned.

E for EMF has been replaced by the Greek letter epsilon ɛ , or ℰ (script capital E, Unicode U+2130).

So the letter E is now ‘electric field.’

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