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Chapter 30 Serway & Beichner. Force between two current carrying wires.

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Presentation on theme: "Chapter 30 Serway & Beichner. Force between two current carrying wires."— Presentation transcript:

1 Chapter 30 Serway & Beichner

2

3 Force between two current carrying wires

4 Electric current The Ampere The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 m apart in vacuum, would produce a force between them equal to 2 × Newton per meter of length.

5 Fig 30-8, p.932

6 Fig 30-9c, p.933

7 Fig 30-1, p.927

8 Fig 30-3, p.929 See Ex. 30.1

9 Fig 30-7, p.931 See Ex. z = 0z >> R

10 Ch. 3010

11 Fig 30-7b, p.931

12 Fig 30-17, p.938

13 Fig 30-12, p.935 for r > R for r < R Application of Ampère’s Law

14 Fig 30-13, p.936

15 Fig 30-19, p.939 Field inside Solenoid

16

17 start 9/13/04

18 Fig P30-20, p.940 Magnetic Flux  B =  BdA = BAcos 

19 Ampère’s Law One More Time Ampere’s law states that the line integral of B. ds around any closed loop equals  o I where I is the total steady current passing through any surface bounded by the closed loop.

20 Apply Ampere’s Law to red loop for a wire with a constant current I Now introduce a capacitor to interrupt the the circuit. What’s wrong? Use a power supply that will keep current constant as the cap is charged: +Q/-Q on left/right plate. Now Apply Ampere’s Law again.

21 Now introduce a capacitor to interrupt the the circuit. If our power supply is strong enough to keep I constant, the gray surface will give B = 0! What’s wrong? Assume that I is constant. Apply Ampère’s Law to either the, white or gray surfaces, both of which are bounded by the red loop. This leads to:

22 If the power supply can keep the current constant, the cap. will be charged: +Q/-Q on left/right plate. This establishes an E-field between the two plates.  E =  EdA = Q/  o Electric flux will change in time corresponding to an effective current called the Displacement Current

23 Consider to different surfaces

24 Fig 30-27, p.945 Orbital Motion of the Electron in an Atom

25 Fig 30-28, p.946 Magnetic Moments due to Spin of electron, neutron and proton

26 Table 30-1, p.946 ElectronProtonneutron Magnetic Moments  J/T

27 Polarization Generated Field points in the opposite direction

28

29 Table 30-2, p.948

30 Paramagnetism Generated field adds to applied field Atomic currents

31 Diamagnetism Generated field opposes applied field

32 Magnetic Domains

33 The Earth as a big magnet

34

35 l =0.4 m i = 10 A

36 Fig P30-6, p.957

37 Ch. 3037

38 Ch. 3038

39 Ch. 3039

40 Ch. 3040

41


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