m2 - E & M - Basic Physical Concepts Electric force and...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: E & M - Basic Physical Concepts Electric force and electric field Electric force between 2 point charges: | F | = k | q 1 || q 2 | r 2 k = 8 . 987551787 10 9 N m 2 /C 2 = 1 4 k = 8 . 854187817 10- 12 C 2 /N m 2 q p =- q e = 1 . 60217733 (49) 10- 19 C m p = 1 . 672623 (10) 10- 27 kg m e = 9 . 1093897 (54) 10- 31 kg Electric field: ~ E = ~ F q Point charge: | E | = k | Q | r 2 , ~ E = ~ E 1 + ~ E 2 + Field patterns: point charge, dipole, k plates, rod, spheres, cylinders, ... Charge distributions: Linear charge density: = Q x Area charge density: A = Q A Surface charge density: surf = Q surf A Volume charge density: = Q V Electric flux and Gauss law Flux: = E A = ~ E n A Gauss law: Outgoing Flux from S, S = Q enclosed Steps: to obtain electric field Inspect ~ E pattern and construct S Find s = H surface ~ E d ~ A = Q encl , solve for ~ E Spherical: s = 4 r 2 E Cylindrical: s = 2 r E Pill box: s = E A , 1 side; = 2 E A , 2 sides Conductor: ~ E in = 0, E k surf = 0, E surf = surf Potential Potential energy: U = q V 1 eV 1 . 6 10- 19 J Positive charge moves from high V to low V Point charge: V = k Q r V = V 1 + V 2 = ... Energy of a charge-pair: U = k q 1 q 2 r 12 Potential difference: | V | = | E s k | , V =- ~ E ~s , V B- V A =- R B A ~ E d~s E =- d V dr , E x =- V x fl fl fl fix y,z =- V x , etc. Capacitances Q = C V Series: V = Q C eq = Q C 1 + Q C 2 + Q C 3 + , Q = Q i Parallel: Q = C eq V = C 1 V + C 2 V + , V = V i Parallel plate-capacitor: C = Q V = Q E d = A d Energy: U = R Q V dq = 1 2 Q 2 C , u = 1 2 E 2 Dielectrics: C = C , U = 1 2 Q 2 C , u = 1 2 E 2 Spherical capacitor: V = Q 4 r 1- Q 4 r 2 Potential energy: U =- ~ p ~ E Current and resistance Current: I = d Q dt = nq v d A Ohms law: V = I R , E = J E = V , J = I A , R = A Power: P = I V = V 2 R = I 2 R Thermal coefficient of : = T Motion of free electrons in an ideal conductor: a = v d q E m = J n q = m n q 2 Direct current circuits V = I R Series: V = I R eq = I R 1 + I R 2 + I R 3 + , I = I i Parallel: I = V R eq = V R 1 + V R 2 + V R 3 + , V = V i Steps: in application of Kirchhoffs Rules Label currents: i 1 ,i 2 ,i 3 ,... Node equations: i in = i out Loop equations: ( E ) + ( iR )=0 Natural: + for loop-arrow entering- terminal - for loop-arrow-parallel to current flow RC circuit: if d y dt + 1 R C y = 0, y = y exp(- t R C ) Charging: E- V c- Ri = 0, 1 c d q dt + R d i dt = i c + R d i dt = 0 Discharge: 0 = V c- Ri = q c + R d q dt , i c + R d i dt = 0 Magnetic field and magnetic force = 4 10- 7 T m / A Wire: B = i 2 r Axis of loop: B = a 2 i 2 ( a 2 + x 2 ) 3 / 2 Magnetic force: ~ F M = i ~ ~ B q~v...
View Full Document

This note was uploaded on 01/20/2010 for the course PHY 1 taught by Professor Erskine during the Spring '10 term at University of Texas at Austin.

Page1 / 13

m2 - E & M - Basic Physical Concepts Electric force and...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online