Coulomb’s Law

Bongjoo Chung

                                                                                                                   

                                                                                                                   

                                                                                                                   

The Basics of Electricity Most of an atom consists of empty

space. If a nucleus is as big as a grape seed,

electron radii is as wide as a football field.

Electromagnetic Force, one of the strongest forces in the world, holds components of an atom together.

The First Glimpse of Electricity

As reported by the Ancient Greek philosopher Thales of Miletus around 600 BC, charge (or electricity) could be accumulated by rubbing fur on various substances, such as amber.

ηλεκτρον (Elektron) means amber.

Electric Charges Protons and

electrons each have qualities called positive electric charge and negative electric charge.

Like charges repel each other, and different charges attract each other.

                  

 

Charges of Matters A matter is said to be charged when

there is an imbalance of protons and electrons.

The greater the accumulation of electrons is, the stronger the charge.

Charge is measured in coulombs (C). An electron is -1.6*10-19 C.

Charles Augustin de Coulomb

Born in 1736, died in 1806

Created a device that helped him develop his theories on charges and electric force and field.

Torsion Balance

Torsion Balance Invented by Coulomb

to measure very weak force

Contributed in the creation of Coulomb’s Law by measuring Coulomb’s Constant

Also used by Henry Cavendish to find the gravitational constant.

Coulomb’s sketch of his invention

How It Works When an unknown

force is applied to the metallic object or plates in the container, the object spins.

The greater the force is, the bigger the angle.

What is Coulomb’s Law The magnitudes of the electrostatic

force between two point electric charges are directly proportional to the product of the magnitudes of each charge and inversely proportional to the square of the distance between the charges.

The strongest formula in the universe

Electrostatic Approximation Coulomb's law is fully accurate

only when the objects are stationary, and remains approximately correct only for slow movement. These conditions are collectively known as the electrostatic approximation.

Similarity to Gravitational Force

Electric force and gravitational force both measure magnitudes of certain forces between two bodies.

Therefore, they are both directly proportional to the magnitudes of two bodies and inversely proportional to the squares of distances.

K, Coulomb’s Constant K = 9*10^9 N*m2/C2

Being one of the constants with biggest numbers, Coulomb’s Constant shows that electromagnetic force is one of the strongest forces in the universe.

Vector of Coulomb’s Law Electric force is a vector force. The first vector value is the sign of

force, since the force can be either negative or positive.

The second vector value is the angle and direction to which the force heads.

Linear Superposition F2 = F1->2 + F3->2

With direction and sign known, multiples of electric forces can be calculated into a net force.

Example The resulting

force is F on 2, since q2 is repelled away by q3 and attracted to q1, because of charge movements.

Electric Field

Every charge has an electric field associated with it.

Electric field of a charge is an area in which the charge has electric force.

Rules in Drawing Field Lines Electric field lines always go from

positive to negative. The stronger the electric field is,

the more the field lines. Dense field line web depicts strong

electric field. Field lines never cross each other. Field Lines

Coulomb’s Law - Field Based on his law, Coulomb was

able to derive another formula. Since this formula is for a single

point charge, only the magnitude of that charge is needed.

E = Kq/d^2

Electric Field of Higher Dimensions

Since e. field of a point charge(0th Dimension) is kq/r^2, those of line charge(2nd) and plane charge(3rd) will become kq/r and kq.

Work Cited Leduc, Steven. Cracking The AP Physics

EXAM.Princeton Review, 2005. Gewirtz, Herman, Barron’s SAT Physics.

Barron’s, 2007 Henderson, Tom. Electric Field Intensity.

Physics Course Class Room. 1996-2007. <http://www.glenbrook.k12.il.us/GBSSCI/PHYS/CLASS/estatics/u8l4b.html

Nave, Carl R. "Electric forces." Hyperphysics. Georgia State University. 30 May      2008 <http://hyperphysics.phy-astr.gsu.edu/hbase/hph.html>.