Moving Electrical Charge Magnetic Field Moving Electrical Charge The Hall Effect The net torque on the loop is not zero. Hall coefficient magnetic dipole moment

Chapter 33 The Magnetic Field of a Current

The Electric Field Due to a Charge

The Magnetic Field Due to a Motion Charge μ 0 is the permeability constant.

The Magnetic Field Due to a Motion Charge The Magnetic Field of a Current Biot-Savart law A straight wire segment

Two Parallel Current Superposition principle Vector sum

The force exerted by one wire on another The definition of the ampere d ibib iaia d ibib iaia Parallel currents attract, and antiparallel currents repel.

Example x P d y

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The Magnetic Field of a Current Biot-Savart law A circular current loop magnetic dipole moment

The Magnetic Field of a Solenoid

If L>>R, The field outside the ideal solenoid is zero. B=μ 0 ni.

The Magnetic Field of a Solenoid The field outside the ideal solenoid is zero. z B -L/2L/2

solenoid for magnetic field parallel-plate capable for electric field E B E=  .

The Electric Field Due to a Charge The Magnetic Field Due to a Moving Charge Gauss’ Law Ampere’s Law

A straight wire segment

Application of Ampere’s law Long, straight wire ( r<R )

A solenoid From loop2, hB 1 + (-h)B 2 =0 loop2 B1B1 B2B2 B 1 = B 2

A toroid Same as a solenoid

The field outside a solenoid

Exercises P , 13, 15 Problems P772 8, 9

A interesting question for interaction force between electric / magnetic field and moving or resting charged particle A charged particle at rest Electric field Moving charged particle Both electric and magnetic field Whether a charged particle moves or not depends on the chosen frame. Whether can we conclude that both electric and magnetic field Depend on the chosen frame? Einstein’s Postulates: The laws of physics are the same in all inertial reference frames. Are these two conclusions contradictory? Is it true?

In the frame K （ at rest ） In the frame K ’ （ with moving electrons ） － － － － － － ＋ ＋ ＋ ＋ ＋ ＋ Ｉ x y r － － － － － － ＋ ＋ ＋ ＋ ＋ ＋ Ｉ x’x’ y’y’ r In the frame K In the frame K ’ Both electric and magnetic force are zero. Magnetic force ： Electric force ： FmFm We have ： Therefore

Transformation equations of E and B: In different inertial reference frame, the results come from the electric or magnetic field is same.