4/10/2014 Electrostatics with Examples

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Electrostatics with Examples

ELECTROSTATICS

Scientist found that if you rub an ebonite rod into silk you observe that rod pulls the paper pieces. Or in

winter when you put off your pullover, your hair will be charged and move. We first examine the structure

of atom to understand electricity better.

Experiments done show that there are three

types of particle in the atom. Two of them are

placed at the center (nucleus) of the atom

which we called proton (p) and neutron (n).

Proton has positive charges “+” and neutron

has no net charge. Third particle is called

electron (e) and they are placed at the orbits of

the atom. They are negatively charged “-”.

Electrons can move but proton and neutron of the atom are stationary.

We show charge with “q” or “Q” and smallest unit charge is 1.6021x10-19 Coulomb (C). One electron

and a proton have same amount of charge.

Positively Charged Particles

In this type of particles, numbers of positive ions are larger than the numbers of negative ions. In other

words numbers of protons are larger than the number of electrons.

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p+>e-

To neutralize positively charged particles, electrons from the surroundings come to this particle until the

number of protons and electrons become equal. Do not forget protons cannot move!

Negatively Charged Particles

In this type of particles, numbers of negative ions are larger than the numbers of positive ions. In other

words numbers of electrons are larger than the number of protons.

e+>p-

To neutralize negatively charged particles, since protons cannot move and cannot come to negatively

charged particles, electrons moves to the ground or any other particle around itself.

Neutral Particles

These types of particles include equal numbers of protons and electrons. Be careful, they have both

protons, neutrons and electrons however, numbers of “+” ions are equal to the numbers of “-” ions.

e+=p-

Conductors

Some of the matters have lots of free electrons to move. It is easy for electrons to flow from these

materials. Metals are good conductors. Gold, copper, human bodies, acid, base and salt solutions are

example of conductors.

Insulators

These types of materials do not let electrons flow. Bonds of the electrons in the insulators are tighter

than the conductors thus, they cannot move easily. Glass, ebonite, plastic, wood, air are some of the

examples of insulators.

Atoms having same charge repel each other and atoms having opposite charges attract each other.

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Example:

Charged

spheres

A, B and

C

behave

like this

under the effect of charged rod D and E. If C is positively charged, find the signs of the other spheres

and rods.

We learned that opposite charges attract each other and same charges repel each other. Using this

explanation we can say that, if the sign of the C is “+” than rod E must be “-” since it attracts C. B must

be “+” since E also attract B. Rod D repels the B so, we say that D must have same sign with B “+” ,

and finally D also repels A, thus A is also “+”.

A(+), D(+), B(+), E(-), C(+)

Electrostatics Exams and Solutions

Next >Types of Charging

Tags: calculations of electrostatics conductors electrostatics insulators negativelycharged particles neutral particles positively charged particles samples of electrostatics

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