CHAPTER 1

PHYSICS FOR JUNIOR HIGH SCHOOL IX

STATIONARY ELECTRIC

PHYSICS FOR JUNIOR HIGH SCHOOL IX

STATIONARY ELECTRIC

Stationary electric is an electric that is motionless for a while in one object.

The first to do this research about stationary electric is Thales of Miletus. He rubbed a stone to wool, and he kept the stone close to chicken feather. Surprisingly, the feather sticked on the stone, and then fall down after minutes.

PHYSICS FOR JUNIOR HIGH SCHOOL IX

STATIONARY ELECTRIC

MAKING AN ELECTRICAL CHARGE OBJECT Neutral object can be turned to be an

electrical charge object by rubbing. Both electrical charge and negative charge

object can pull the neutral object. The separation of electrical charge in neutral

object caused by bringing an elctrical charge object nearer called electric induction.

A plastic ruler that is rubbed to wool can pull the small pieces of paper. The pieces can be pulled by ruler because it has been a negative electrical charge object.

The ruler is held by hand

Neutral glass Positive charge

glass

Neutral silk

Negative charge silk

PHYSICS FOR JUNIOR HIGH SCHOOL IX

STATIONARY ELECTRIC

ELECTRICAL CHARGE OBJECTAtom considered as a negative charge if containing more elctron, while atom considered as a positive charge one if lack of electron. When it is considered as a neutral one if the total electron and proton is equal.

Electrical charge can not be observed by naked eye, but its effect and phenomenon can be felt. The total charge of proron and electron are equal, but the kinds are differnt. Positive charge (proton) simbolized by “ + “, while negative charge (electron) simbolized by “ – “.

PHYSICS FOR JUNIOR HIGH SCHOOL IX

STATIONARY ELECTRIC

BALLOON AND WOOLIf we rub balloon to wool, the electron will move from wool to balloon.So that ballon becomes a nefative electrical charge and the wool is a positive electrical charge.

PHYSICS FOR JUNIOR HIGH SCHOOL IX

STATIONARY ELECTRIC

GLASS AND SILKIf we rub a glass to silk, electron will move from glass to silk. So, the glass turned to be a positive electrical charge and the silk is a negative electrical one.

PROPERTY OF ELECTRICAL CHARGE

STATIONARY ELECTRIC

PHYSICS FOR JUNIOR HIGH SCHOOL IX

PHYSICS FOR JUNIOR HIGH SCHOOL IX

STATIONARY ELECTRICPROPERTY OF ELECTRICAL

CHARGE 2 electrical charge objects has properties as

follows:- if the charge contained is equal, it will

push one to other- if the charge contined is different, it will

pull one to other. - Neutral objects is always pulled by electrical charge object.

INDUCTION BY ELECTRICAL CHARGE OBJECT

Without rubbing, we can also give electrical charge to an object by inducing to another electrical charge object.

STATIONARY ELECTRIC

PHYSICS FOR JUNIOR HIGH SCHOOL IX

PHYSICS FOR JUNIOR HIGH SCHOOL IX

STATIONARY ELECTRIC

Refulsive power or tractive power between two elecrical charge objects called Coulomb Force, it is as an admiration for Augustin de Coulomb, a physicist form France who is the first to observe electrical force and formulated it mathematically.

Coulomb Laws

PHYSICS FOR JUNIOR HIGH SCHOOL IX

SATIONARY ELECTRIC

Coulomb Laws : “ The magnitude of repulsive and tractive power between two electrical charge objects is directly proportional to the quantity of each electrical object and inversely proportional to space-square between the two charged-objects. Mathematically, Coulomb Laws can be stated as follows :

Coulomb Laws

PHYSICS FOR JUNIOR HIGH SCHOOL IX

STATIONARY ELECTRIC

DETERMINING ELECTRICAL CHARGE OBJECT

To know whether an object is an electrical object or not, we can bring it nearer to the neutral electroscope.

PHYSICS FOR JUNIOR HIGH SCHOOL IX

STATIONARY ELECTRIC

VAN DE GRAAFF GENERATOR

Van de Graaff is a generator that produces a great stationary electric.

Metal cylinder

Politen Cylinder

Elastic Belt

PHYSICS FOR JUNIOR HIGH SCHOOL IX

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