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Презентация была опубликована год назад пользователемЭлла Скобельцына

1 0. Note to Lectures 8-9: CONDUCTORS OF 1 ST AND 2 ND TYPE Absolute temperature T Resistivity Superconductivity 0 Conductors of TYPE 1 (metals) Conductors of TYPE 2 (electrolytes, semi- conductors)

2 Note to Lectures 8-9: CONDUCTORS OF 2 ND TYPE Absolute temperature T Resistivity 0 Conductors of TYPE 2 (electrolytes: IONs!, semiconductors)

3 * Short Notes to the Lecture of April 19th Kirhhof Laws 1 & 2

4 Independent loops A loop that has a branch that does NOT belong to any other loop, is an INDEPENDENT CIRCUIT LOOP (contour). These three circuits are independent (any next circuit such as green shown on he next page will be dependent).

5 Dependent loops If all branches of a loop belong also to other loop(s), such circuit loop is a DEPENDENT CIRCUIT LOOP (thus 2 nd Kirhhoffs Law is not considered for such): Here, the circuit shown in green colour would be dependent once the black, red, and blue are considered independent.

6 Dependent loops The same is about 2 more dependent circuits you can guess on this scheme. In fact, ANY 3 of the 6 available here close loop circuits will be independent, but then the remaining 3 would be dependent ON THEM.

7 Linearly dependent equation(s) For dependent circuits there is no need to produce the 2 nd Kirhhoffs Law because it would be excessive / needless / superfluous / redundant.

8 As for the 1 st Kirhhoffs Law, it is necessary and sufficient to consider (N-1) nods: the Nth nod would be superfluous (excessive) to consider (gives linearly dependent – thus REDUNDANT equation).

9 MAGNETIC FIELDS PH121 (Lectures 10, 11)

10 PLAN 1.Lorentz Force. 2.Amperes MAGNETIC Force. 3.Magnetic Induction B (Tesla). Biot-Savart Law. 4.Magnetizing force H (A/m). 5.Amperes Law. 6.Magnetic Flux. 7.Magnetic Field of a Solenoid. Helmholtz coils. 8.FARADAYs LAW of INDUCTION. Lentzs Rule (Law). Motion EMF. 9.Self-induction (Inductance) L.

11 SERWAY, Chapter (pp. 894 – 1032). RECOMMENDED LITERATURE to the TOPIC Magnetic Field: HALLIDAY, RESNICK, WALKER Chapter (pp ).

12 1. LORENTZ FORCE

13 …where: B – magnetic induction (SI: Tesla), v – velocity (m/s), q – charge (Clmb) of a particle on which the force is exerted on behalf of electric field E and magnetic field B.

14 LORENTZ FORCE

15 LORENTZ FORCE (continued)

16 2. AMPERES MAGNETIC FORCE where I – current (Amp), B – magnetic induction (SI: Tesla), L – length of the conductor (m). vector (cross) product

17 Direction of Amperes Force

18 MAGNETIC FORCE (continued)

19 3. Magnetic induction Biot-Savart Law where magnetic constant (permeability of free space) 0 =4 10 – 7 Henry/m

20 4. Magnetizing Force H H = B / 0 where is magnetic permeablity for all media except ferromagnetics, =1); [H]=Amp/m

21 5. AMPERES LAW (Law of Total Current)

22 6. MAGNETIC FLUX

23 7. Magnetic Field of a Solenoid

24 HELMHOLTZ COILS

25 Here, the MAGNETIC FLUX will be changing when BCD moving:

26 Current Rating (PH121) PH121TUT's PAPER 1 PAPER 2 SUM DATES 24.мар05.апр12.апр19.апр Pts ABEL BONIVENTURE 1 1 BADOKUFA PROSPER H BAKARI BONIFACE J. 0 0 CHACHA MARWA 1 0 CHALLO BONIFACE S. 0 0

27 Current Rating (PH121) FELIX FESTUS GHATI CHARLES 10 1 HALFANI OMARI HINJU NATHANIEL A. 0 0 HOROMA FIDEL 11 2 IKELYA NYANDA 2 1 JAJI KIZITO 0 0

28 Current Rating (PH121) JUMA JUMA M. -0,5 LIWAHA ERNEST H. 0 0 MAFTAHA MGENI M MICHAEL THAMOS MTERA ELIREHEMIA Z. 0 0 MWENDI CARITAS D. 0 0 MWENYEMBEGU AGREY R.

29 Current Rating (PH121) NDEMU SELEMAN M. 0 0 RABACH DUMA R RAPHAEL PASCAL SAIDI JUMA 0 0 SALIM MWANAIDI 2 -0,5 1,5 SHIJA PAUL 2 -0,52 3,5 WYCLIFE OTENYO

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