Ch 15 physics

• Electrons

  negatI’ve, charge = -1.6 x 10^-199; mass = 9.11 x 10 ^-31
• Proton

  Positive, 1.6 x 10^-19; mass 1.67 x 10^ -27
• Neuron

  Neutral, 0: mass 1.67 x 10^-27
• Coulomb,s Law


  It is directed along the line joining the two particles and inversely proportional to the square of the separation distance, r, between them

  – It is proportional to the product of the magnitudes of the charges, |q1|and |q2|on the two particles

  – It is attractive if the charges are of opposite signs and repulsive if the charges have the same signs
• Coulomb constant


  ke =8.99x10^9
• Electric Force


  F = ke |q1| |q2| / r^2
• Conversions

  Conversion chart

  
• Electric Field


  Exist in the region of space around a charged object; E = F/q, E= keQ/r^2: unit N/C
• Electric Dipole

  Two equal and opposite charges
• Electric Flux


  A measure of how much the electric field vectored penetrate through a given surface ;ΦE = E A cos θ unit: N m^2/C
• Gauss’ Law


  States that the electric flux through any closed surface is equal to the net charge Q inside the surface divided by εo. εo is the permittivity of free space and equals 8.85 x 10-12 C2/N.m2

  – The area in Φ is an imaginary surface ΦE = Q/ εo
• Calculation of the field outside the shell is identical to that of a point charge

  E = Q/ 4πr^2, E=keQ/r^2
• Total Charge


  Q=σA

  E = σ/ 2εo
• Total electric field between the plates 


  E = σ/εo