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FORCE BETWEEN CHARGES. CHARLES COULOMB (1738-1806). 1780’s: Invented the torsion balance to investigate the relationship between charge, force, and distance. He established the fundamental law of electrostatic force. Coulomb’s Law.
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CHARLES COULOMB (1738-1806) • 1780’s: Invented the torsion balance to investigate the relationship between charge, force, and distance. He established the fundamental law of electrostatic force.
Coulomb’s Law • For charged objects that are small compared to the distance between them, the force between the objects varies directly as the product of their charges and inversely as the square of the distance between them.
Coulomb’s Law • F 1/ r2 • F q1 q2 (product of the charges) F = k q1q2/ r2 • F = electrostatic force • q1 and q2 = charges • r = distance between charges • k = Coulomb constant = 8.99 x 10 9 N*m2 / C2
Coulomb’s Law • If q1 and q2 are opposite sign, then F is attractive(F < 0) • If q1 and q2 are same sign, then F is repulsive(F > 0) • Coulomb’s law applies only to point charges (particles) or spherical charge distributions. For spherical charge distributions, r is the center-to-center distance.