Coulomb's_Law

=Introduction= toc Coulomb's Law is the relationship among electrical forces, charges, and distance. It is like Newton's Law of Gravity.

=Important Information=

the SI unit of measure for electrical charge is a Coulomb (C). Charge of 1 Proton is +1.6x10^ -19. Charge of 1 Electron is -1.6x10^ -19.

F=Force K=electrical proportion constant= 9.0* 10^2 N*m^2/c^2 q=charge (c for coulomb) d=Distance (m)

REMEMBER! The charge(q) of a particle is NOT a vector quantity. Therefore, when described as positive or negative, that tells whether it is a proton or electron. DO NOT PUT NEGATIVES ON THE FORMULA!!!!

Understanding the Concept
The example picture above implies that exactly the same magnitude of force acts on q2.

However, they are different in two ways. First off, the force due to gravity is always //**__ attractive __**//. And second, the magnitudes of the two forces are vastly different. Consider the ratio of the electrical and gravitational forces acting on two particles. This ratio is a constant, independent of the relative positions of the particles Coulomb's law is a vector equation and includes that the force acts along the line joining the charges. Like charges repel and unlike charges attract. Coulomb's law describes a force of infinite range which obeys the inverse square law, and is of the same form as the gravity force.

//C// __ //oulomb's law has the same mathematical form as Newton's law of gravity//. __



The constant "k" appearing in Coulomb's Law is often called __**Coulomb's Constant.**__

When describing the electric forces in atoms and nuclei, it is often convenient to work with the product of Coulomb's constant and the square of the electron charge since that product appears in electric potential energy and electric force expressions.

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Example using GUESS Method
G: d= .030m qA= 6.0 c qB= 3.0 c

U: F= ?N

E: F=kqAqB/d^2

S: (9.0x10^9)(3.0c)(6.0)/ .030m^2

S: F= 1.8x10^14 N

Try it out!
Problem # 1: One charge of 2.0 C is 1.5m away from a –3.0 C charge. Determine the force they exert on each other.