·10^{−3} Q = 4 = 4 · 10^{−3} d = 3 = 3 · 10^{−2}

·\frac{q·Q}{d^{2}} = 9· 10^{9}· \frac{12·10^{−3}·4·10^{−3}}{(3·10^{−2})^{2}}

= 4, 8 · 10^{8}

·10^{−3} d = 5 = 5 · 10^{−2} q =

Q

·10^{−3} = 9· 10^{9}· \frac{q·q}{(5·10^{−2})^{2}} ⇒

9· 10^{9}· q^{2} = 5· 10^{−3}· (5·

10^{−2})^{2} ⇒ q^{2} =

\frac{5·10^{−3}·(5·10^{−2})^{2}}{9·10^{9}} = 1, 38·

10^{−15} ⇒ q = 3, 73·

10^{−8} = 37, 3

∑ q = q+Q = 2·q = 74, 6

24/2 = 12 pommes

·10^{−6}etchaquelectronunecharge, ditelmentaire, de1, 6 · 10^{−19}.Ainsi, lenombred′lectronsvaut : n =

\frac{7·10^{−6}}{1,6·10^{−19}} =

4, 375 · 10^{13}electrons

Q_{noyau} =

6· e e q_{électron} = e ·10^{9}·

\frac{1,6·10^{−19}·6·1,6·10^{−19}}{(10^{−10})^{2}}

= 1, 38 · 10^{−7} = 138 e = k· \frac{q_{proton}·q_{électron}}{d^{2}} = 9· 10^{9}· \frac{(1,6·10^{−19})^{2}}{(10^{−10})^{2}}

= 2, 3 · 10^{−8} g =

G· \frac{m_{proton}·m_{électron}}{d^{2}} = 6, 67·

10^{−11}·

\frac{1,67·10^{−27}·9,1·10^{−31}}{(10^{−10})^{2}}

= 10^{−47}

r = \frac{2, 3 · 10^{−8}}{10^{−47}} = 2, 3·10^{39}

2, 3·

10^{39} P = m·g = (m_{e}+m_{e})·g = 2·m_{e}·g

F = k·\frac{e · e}{d^{2}} = 2·m_{e}·g ⇒

9·10^{9}·\frac{(1, 6 · 10^{−19})^{2}}{d^{2}} = 2·9, 1·10^{−31}·10 ⇒

d^{2} = 9·10^{9}·\frac{(1, 6 · 10^{−19})^{2}}{2 · 9, 1 · 10^{−31} · 10} = 12, 66 ⇒

d = 3, 56 q Q d

F = 400 mN = 400·10^{−3} = 9·10^{9}·\frac{q · Q}{d^{2}}

q Q

d d′ = d/9

F′ ·\frac{q·Q}{d^{′2}} = k· \frac{q·Q}{( \frac{d}{9} )^{2}} =

k· \frac{q·Q}{\frac{d2}{81}} = k· \frac{q·Q}{d^{2}}·

81 = 400·