Two identical conducting spheres, fixed in place, attract eachother with an elec

Question

Two identical conducting spheres, fixed in place, attract eachother with an electrostatic force of 0.138 N when theircenter-to-center separation is 72.3 cm. The spheres are thenconnected by a thin conducting wire. When the wire is removed, thespheres repel each other with an electrostatic force of 0.0524 N.Of the initial charges on the spheres, with a positive net charge,what was (a) the negative charge in coulombs onone of them and (b) the positive charge incoulombs on the other?

(a)

Number

Units

Explanation / Answer

Assume negative charge is -q, positive charge is Q F = 0.138 N, r = 0.723 cm. F = kqQ/r2 so qQ = Fr2/k = 8.015*10-12C2F ' = 0.0524 N, each charge becomes (Q - q)/2 F ' = k(Q - q)2/(4r2) so Q - q = 2r (F '/k) = 3.489*10-6 C (Q + q)2 = (Q - q)2 + 4qQ so Q + q = [(Q - q)2 + 4qQ] =6.651*10-6 C so Q = (6.651*10-6 C + 3.489*10-6 C)/2 =5.07*10-6 C q = 1.58*10-6 C answer: a) -1.58*10-6 C b) 5.07*10-6 C

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.