PHY 03 Lesson 1.1: Electrostatics (Electric Charge)

ELECTRICITY

CAME FROM THE GREEK WORD "ELEKTRON" which means "amber".

ELEKTRON

GREEK WORD which means "amber".

Amber

is a yellow or reddish-brown stone used in jewelry.

When ____________ was rubbed, it developed an electrical charge that allowed light objects like straw and feathers to be lifted.

Electric charge

can be defined as a fundamental property of subatomic particles that gives rise to the phenomenon of experiencing force in the presence of electric and magnetic fields.

Positive charges

Negative charges

Two main types of electrical charges

Electrons

are the negatively charged particles of atom.

- Orbit an atomic nucleus at a relatively great distance.

- Located outside the atomic nucleus.

- Electrons are much smaller than protons or neutrons.

- Negatively charge ( - )

- Mass: 9.109 x 10-28 grams

- Charge: 1.602 x 10-19Coulombs

Protons

are the positively charged particles of atom.

-The most basic unit of an atom is the proton

- Located inside the atom's nucleus

- Positively charge ( + )

- Mass: 1.673 x 10-24grams

- Identity of an element

- Charge: 1.602 x 10-19Coulombs

Neutrons

are a type of subatomic particle with no charge (they are neutral).

• Electric charges is a physical quantity

can be quantified by measurement

• Electric charges is quantized.

This means that the charge values are discrete. (0, -1, +1; q = 1.602 × 10^-19 C )

• Symbol of electric charge is "q" or "Q"

• Unit of electric charge is the coulomb (C)

1 coulomb= 6.242x10^18 e

Characteristics of ELECTRIC CHARGES

6.242x10^18 e

coulomb (C)

Like charges repel each other

Opposite charges attract each other

LAW OF CHARGES

IONS

• An ion is an atom or group of atoms that has an electric charge.

• An atom that has an imbalance in the number of protons and electrons.

• Ions with a positive charge are called cations.

• Ions with a negative charge are called anions

cations

positively charged ions

anions

negatively charged ions

electrons

are the essence of electricity

go from your hair to the balloon are easily transferrable

Static electricity

is the result of an imbalance between negative and positive charges in an object.

❑Conductors

❑Insulators

❑Semiconductors

❑Superconductors

Materials can be classified according to how they allow the transfer/flow of electrons.

conductor

substance that can easily transfer electric charge

insulator

substance that does not transfer electric charge

Semiconductors

are materials which have a conductivity between conductors (generally metals) and nonconductors or insulators (such as most ceramics).

superconductor

is defined as a substance that offers no resistance to the electric current when it becomes colder than a critical temperature.

Some of the popular ___________ of superconductors are aluminum, magnesium diboride, niobium, copper oxide, yttrium barium, Vanadium-gallium, and iron pnictides.

❑ Charging by friction/rubbing

❑ Charging by conduction/contact

❑ Charging by induction

METHODS OF CHARGING

CHARGING BY FRICTION

•Electrically neutral body can gain a charge by rubbing or friction.

•It is because of the difference in their material compositions and attraction for the electrons.

Electrons moves from your hair to the balloon because atoms in the rubber have a greater attraction for the electrons.

CHARGING BY CONDUCTION

Refers to the technique of charging an uncharged material by bringing it near or touch with some other charged material

CHARGING BY INDUCTION

Induction charging is a charging method that charges an object without touching the object to any other charged object.

Electric polarization

refers to the separation of center of positive charge and the center of negative charge in a material.

ELECTRIC DIPOLES

is defined as a couple of opposite charges "q" and " -q" separated by a distance "d".