Question

Two point charges of equal magnitude are 7.5cm apart. At the midpoint of the line connecting them, their combined electric field has a magnitude of 49N/CFind the magnitude of the charges (pC)

Answer 1

q 1 = q 2 = Q

E = k * Q / r²

The combined electric field:

E = 2 * k * Q / r²

k = 9 · 10^9 Nm²/C²

r = 0.075 : 2 = 0.0375 m

45 N/C = 2 · 9 · 10^9 · Q / 0.0375²

45 = 18 · 10 ^9 Q / 0.0014062

Q = 45 · 0.0014062 / 18 · 10^9

Q = 0.003515 · 10^(-9) C

Q = 3.5155 · 10 ^ (-12) C = 3.5155 pC