Review for 2 nd Midterm

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Baldric Austin
5 years ago
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1 Review fo 2 nd Midtem

2 Midtem-2! Wednesday Octobe 29 at 6pm Section 1 N100 BCC (Business College) Section NR (Natual Resouces) Allowed one sheet of notes (both sides) and calculato Coves Chaptes and homewok sets #5-8 Send an to you pofesso if you have a class conflict and need a make-up exam Review in class on Tuesday, Octobe 28th

3 Cuent and Resistance! Cuent i! Cuent density dq dt i J da! If J is unifom and paallel to da i JA

4 Cuent and Resistance Ohm s law V ir Powe lost to heat enegy in a esisto P i 2 R P V 2 R P iv

5 Loop Rule E i ir 0 i E + R! Gaphical epesentation

6 Cicuits V V b a ir! Substituting fo i gives V b V a E R R +

7 Cicuits! Resistos in seies! Resistos have identical cuents, i! Sum of V s acoss esistos applied V E.! R eq is sum of all esistos n R R eq j j 1

8 Cicuits! Resistos in paallel! Resistos have identical V E! i 1 V/R 1 etc! R eq given by 1 R eq 1 R R R 3

9 Junction Rule! Abitaily label cuents, using diffeent subscipt fo each banch! Using consevation of chage at each junction i i in out! At point d! At point b i + i i i + i i 1 3 2! At point a! At point c i i 1 1 i i 2 2

10 Cicuits What is i 1? R 1 R 2 R 3 R 4 2 ohm E5 V

11 Cicuits What is i 2? Thee unknowns so we need thee equations E i R i R i R i R + i R i + i i i 2 i 1 R 3 ( R + R 3 2 )

12 Motion in a B Field! Foce on a chaged paticle due to a magnetic field is F B qv B! F B does not change the speed (magnitude of v ) o kinetic enegy of paticle! Chaged paticles moving with v to a B field move in a cicula path with adius, mv qb! Foce on a cuent caying wie due to a magnetic field is F B il B

13 Motion in a B Field Right-hand hand ule Fo positive chages - when the finges sweep v into B though the smalle angle φ the thumb will be pointing in the diection of F B! Fo negative chages F B points in opposite diection

14 Motion in a B Field! Cicula motion! Peiod (time fo one evolution) T mv qb 2π 2π m v qb! Fequency (the numbe of evolutions pe unit time) f 1 T! Angula fequency: ω 2π f

15 B Fields fom Cuents! Biot-Savat law i ds db 4 3 µ 0 π

16 B Fields fom Cuents! B field a distance R fom a long staight wie caying cuent i B µ 2 0 π i R! B field is tangent to magnetic field lines

17 B Fields fom Cuents! ight-hand hand ule! Point thumb in diection of cuent flow! Finges will cul in the diection of the magnetic field lines due to cuent

18 B Fields fom Cuents! B field at the cente of an ac is B µ 4 0 π i φ R! Expess φ in adians! Fo a complete loop (φ 2π) 2 ) then B is B µ 0 i 2R

19 B Fields fom Cuents! Foce on a wie caying cuent, i 1, due to B of anothe paallel wie with cuent i 2 F µ 0Li1i 2πd! Foce is attactive if cuent in both wies ae in the same diections! Foce is epulsive if cuent in both wies ae in the opposite diections 2

20 B Fields fom Cuents! Fo symmetic distibutions of chage use Ampee s law to calculate B field B d s µ 0 i enc! Integal aound closed loop called Ampeian loop

21 B Fields fom Cuents! Use the ight-hand hand ule to detemine the signs fo the cuents encicled by the Ampeian loop! Cul ight hand aound Ampeian loop with finges pointing in diection of integation! Cuent going though loop in the same diection as thumb is positive.! Cuent going in the opposite diection is negative.

22 B Fields fom Cuents! Fo ideal solenoid: B µ 0 in! n is # tuns/length! Fo tooid B µ 2 0 π in

23 Cuents fom B Fields! Magnetic flux Φ B B da! Faaday s law (N loops)! Lenz s law induced emf gives ise to a cuent whose B field opposes the change in flux that poduced it E N dφ dt B

24 Φ B B da Faaday s law BAcosθ We can change the magnetic flux though a loop (o coil) by: E N dφ dt B! Changing magnitude of B field within coil! Changing aea of coil, o potion of aea within B field! Changing angle between B field and aea of coil (e.g. otating coil) db E NAcosθ dt da E NBcosθ dt d(cosθ) E NBA dt

25 Geneatos! Geneato with N tuns of aea A and otating with constant angula velocity, ω! Magnetic flux is Φ B! Emf is BAcosωt E NBAω sinωt t

A moving charged particle creates a magnetic field vector at every point in space except at its position.

A moving charged particle creates a magnetic field vector at every point in space except at its position. 1 Pat 3: Magnetic Foce 3.1: Magnetic Foce & Field A. Chaged Paticles A moving chaged paticle ceates a magnetic field vecto at evey point in space ecept at its position. Symbol fo Magnetic Field mks units