Ch. 29 Magnetic Field :

1. Ch. 29 Magnetic Field : B § 29-1 Magnetic field q1 q2 E field charge charge continuous I1 (current) B field I2 상호작용 (B를 매개로) moving charge ex) I1 I2 § 29-2 The definition of B • Magnetic field line

2. § 29-3 Crossed Fields L + + + 2 v - 1 - - - E B E와 B가 적절히 걸리면 전자는 1 E만 걸려 있는 경우(B=0) 2 Thomson 1897 전자발견 1906 Nobel Prize Millican 1910 1923 Nobel Prize (measurement of q/m of electron)

3. § 29-4 Hall Effect 1. If  is the charge carrier, then  charge pile up at the right So point y is at a higher position than point x +e 2. If  is the charge carrier, then  charge piles up at the right So point y is at a lower position than point x -e 3. To calculate ncu (number density: number/unit volume)

4. § 29-5 A Circulating charge Fc 소 : Mirror B field 양쪽 끝부분의 Bfield가 세기 때문. 일부 charged particle의 반사가 양끝에 일어난다. Trapping (Van Allen radiation belt) 일부 charged particle은 통과해 나감. : Aurora 형성(극지방) 밀 밀 trapped charged particles in Van Allen belt (PLASMA) Solar wind

5. § 29-6 Cyclotron § 29-7 Magnetic force on a current-carrying wire

6. Fig 29-21 B: out of paper L/6 i L/3 L/3 L/3 F1 F3 F2 Note: 힘은 같은 길이의 straight line wire에 걸리는 힘과 같다. (F1=F2=F3) segment의 geometry에 무관(if wire is rigid)

7. B F F § 29-8 Torque on a current loop N S 4 1 3 2 Figure a) 위에서 본 경우 Figure b) B 방향으로 본 경우 그리고 힘의 공통작용선이 같은 선이므로 net torque도 0 Figure c) Side 2에서 본 경우 그러나 힘의 공통작용선이 다른 선상이므로 net torque가 발생 N번 감긴 loop 경우 A:area enclosed by coil

8. p p § 29-9 The magnetic dipole • magnetic dipole moment : • torque : electric dipole moment : torque : cf) • magnetic potential energy cf) electric dipole potential energy -q +q +q -q E Lowest Energy Highest Energy