Physics 112 Formulae

Fundamental Constantsρair (density of air) = 1.2 kg/m3 (20oC, 1 atm); speed of sound in air = 344 m/s (20oC, 1 atm) e = 1.602176487 X 10-19 C k = 1/4πεo = 8.987551787 X 109 N m2/C2

me = 9.109382 X 10-31 kg εo = 8.854187817 X 10-12 C2/Nm2

mp = 1.672621 X 10-27 kg μo = 4π X 10-7 T m/A (exact)

mn = 1.674927 X 10-27 kg c= 1√ε o μo

=299,792,458 m /s (exact)

UNIT 1: Charges, Coulomb’s Law, Gauss’s Law

Coulomb’s Law: |F⃗12|=k q1 q2

r122 = 1

4 π ε o

q1 q2

r122 ; F⃗=q E⃗

Point: |E⃗|= kqr2 = 1

4 π εo

qr2

Line: |E⃗|=2kλr

= 12π ε o

λr

Plane: |E⃗|=2πkσ= σ2 εo

∨ σεo

if conducting plane

ΦE=∫ E⃗ ∙d A⃗=∫E⏊ dA=∫E cos φ dA; Gauss’s Law: ∮ E⃗ ∙ d A⃗=qins

εo=4 πk qins