Questions:
 A charge Q1 = 810–6 C at M (2,5,8) and a charge of Q2 = –510–6
  C at N (6,15,8) are located in a vacuum. Determine the force
  exerted on Q2 by Q1.
 A cuboidal box penetrates a huge plane sheet of charge with
  uniform surface charge density 2.5 ×1 0−2such that its smallest
  surfaces are parallel to the sheet of charge. If the dimensions of
  the box are 10 cm × 5 cm × 3 cm, then find the charge enclosed by
  the box.
 Find the total charge inside the volume indicated by ρ v = 4xyz2, 0 ≤
  ρ ≤ 2, 0 ≤ Φ ≤ π/2, 0 ≤ z ≤ 3. All values are in SI units.
 A long thin rod of length 50 cm has a total charge of mC uniformly
  disturbed over it. Find the linear charge density.
 He’s a French army Engineer who performed an elaborate series
  of experiments using devices. He is the one who invented the
  Coulomb’s law.
Answers:
  1. R= r2-r1
            = (6ax, 15ay, 8az) – (2ax, 5ay, 8az)
            = (4ax + 10ay)
             R
     a=   ¿ R∨¿ ¿
            = √ ¿ ¿ = 10.77
                ( 4 a x + 10 a y )
            =        10.77
            1 Q1 Q2
     F=   4 π ε0 ¿ ¿
                                                   −6        −6
                       1         (8 ×1 0 )(−5 ×1 0 )
            ¿                −12
              4 π (8.854 ×1 0 )           ¿¿
                                     ( 4 a x +10 a y )
            = (−3.1 ×1 0−3 )(            10.77
                                                         )
            = (−1.15 a x −2.88 a y ) mN
 2.
      = 5 cm × 3 cm        = 15 cm2
                       = 15 × 10–4 m2
Charge density;
               σ= 2.5 ×10–2 Cm–2
Charge enclosed;
               q=σA
                   = (2.5×10−2) (15×10−4)
                                  = 37.5×10−6C
                                  = 37.5µC
 3.
                                                          2
                           ρ v =4 ⋅ ρsin φ⋅ ρ cos φ ⋅ z
                              π
                       3      2   2
      Q=∫ ρv dv
         vol
                      ¿∫     ∫ ∫ (4 ⋅ ρ sin φ ⋅ ρ cos φ ⋅ z 2 )(dρ ⋅ ρdφ⋅ dz)
4.
       q=5
       mC = 5 × 10–3 C
       l= 50 cm = 0.5 m.
       λ =?
   q
λ= l
                 −3
           (5 ×1 0 )
       =       0.5        = 10−2 Cm−1
  5.
               Charles – Augustin de Coulomb