Hukum Ampere.

Presentasi berjudul: "Hukum Ampere."— Transcript presentasi:

1 Hukum Ampere

2 Ampere’s Law

3 Medan magnetik dari kawat lurus panjang
gunakan Hk Biot-Savart I B Ambil vektor pendek , ds ds Perkalian skalar antara B & vektor pendek ds adalah:

4 Jumlah B.ds di sekitar lintasan lingkaran
Jumlahkan ini untuk seluruh cincin ds Keliling lingkaran

5 Jumlah B.ds di sekitar lintasan lingkaran
N.B. this does not depend on r In fact it does not depend on path Ampere’s Law: on any closed loop where I is the current flowing through the loop

6 Hukum Ampere Sign comes from direction of loop, current & right hand rule B I I B I I

7 Sign comes from direction of loop, current & right hand rule
Hukum Ampere B I B I I B I I

8 Hukum Ampere No Different Physics from Biot-Savart Law
Useful in cases where there is a high degree of symmetry C.f. Coulomb’s Law and Gauss’s Law in electrostatics

9 Quiz c Currents of 1A, 5A, 2A, flowing in 3 wires as shown a b 1A
What is B.ds through loops a, b, c, d? 5A 2A B.ds -1m0 +3m0 +4m0 +6m0 a b c d

10 Examples of using Ampere’s Law

11 Examples Long-straight wire Insider a long straight wire Toroidal coil
Solenoid

12 Long Wire

13 Magnetic Field from a long wire
By symmetry r I Ampere’s Law on Loop 2 B||(r1) Loop1 Br2 Br1 B||(r1)

14 Magnetic Field from a long wire
For any closed Ampere Loop the radial components will always cancel out By symmetry Br3 Br4 Loop 2 Br1 Br2 Loop 3 Br1 Thus there is no way to balance a current by a radial component or produce a radial component from a current Br2

15 Magnetic Field from a long wire
Tangential component Take a circle of radius r as the Ampere Loop r I Tangential component By symmetry at constant r L.H.S. or L.H.S. = R.H.S Q.E.D.

16 Di dalam suatu kawat

17 Di dalam suatu kawat berarus I0
Kita pilih loop Ampere berupa lingkaran dengan jari-jari r Asumsikan rapat arus adalah homogen sehingga arus yang mengalir dalam loop adalah Sama seperti sebelumnnya r A

18 Medan B dari suatu kawat panjang

19 Toroidal Coil

20 Toroidal Coil I0 r Toroid has N loops of wire, carrying a current I0
Ampere Loop, circle radius r No current flowing through loop thus B = 0 inside the Toroid

21 Toroidal Coil Ampere Loop, circle radius r I0 r
For each wire going in there is another wire comeing out Thus no nett current flowing through loop thus B = 0 outside the Toroid

22 Toroidal Coil I0 r Zoom Toroid has N loops of wire
For each loop of the coil an extra I0 of current passes through the Ampere Loop Ampere Loop, circle radius r

23 Medan B di dalam Toroida
Toroid berbentuk donut dengan dililiti koil. Maka, ds r

24 Solenoid

25 Infinitely Long Solenoid
Wire carrying a current of I0 wrapped around with n coils per unit length Zoom looks very similar to the toroid with a very large radius

26 Infinitely Long Solenoid
Wire carrying a current of I0 wrapped around with n coils per unit length Field at centre is same as torus of infinite radius

27 Medan magnet di dalam Solenoida
Jika solenoida terdiri dari jumlah lilitan N dan panjang adalah l, maka: l ds

28 Resume Hukum Ampere Contoh
Lebih mudah dipakai dibandingkan Hukum Biot-Savart dalam banyak kasus Contoh Kawat panjang Dalam kawat Toroida Solenoida