Static Electricity

Static By Aries Triwidajati S. SMP Negeri 2 Cileunyi

Key word Electrostatic

Neutral

Electrically charge

Comb

Rub Negative charge Positive charge Proton Electron

Hair Attract Repulse Balloon Neutron

Static Electric

Basic Competence Students are able to apply the

electricity concept to understand the symptoms of electrostatics.

Indicator Explaining that an object can gain

electric charge by being rubbed.

What Is Static Electricity? A stationary

electrical charge that is built up on the surface of a material

Matter is made up of atoms. –

+

Proton (positive charge)

+ + –

neutron (neutral) +

–

electron (negative charge)

–

atom

nucleus

If electrons = protons

neutral

If electrons > protons negative charge

gaining electrons,

If electrons < protons positive charge

losing electrons,

Two kinds of charges After being rubbed, a plastic ruler can attract paper scraps. Ruler carries electric charge. It exerts electric force on paper. This charging method is called charging by friction. The interaction between static electric charges is called electrostatics.

A pp ar atus a nd ma te rial s 1.

1 comb / ruler

2.

Tissue paper

Procedur 1. e Put pieces of

tissue paper on the table

2. Rub the comb against your hair, bring it close to the tissue paper. Write what can you see.

8. Let the tissue paper cling on the comb for a few seconds. Write what you can see after a few seconds

Hair and comb area neutral. An atom is neutral because the positive and negative are in balance. When you rub the comb against your hair, a number of atoms in your hair are disturbed so that a number of electrons will be released and moved toward your comb. As result, your comb gains more electrons and it is no longer neutral, but negatively charged. Your hair lost electron, So it is positively

This event is an example of gaining electrostatics by rubbing. Electrostatics are the accumulation of electric charges an object. Think about other examples of electrostatics.

Analysis; 1. What kind of charges do the comb and your hair have before being rubbed against each other. Before being rubbed the comb and the hair are neutral 3. What kind of charges do the comb and your hair have after being rubbed against each other. After being rubbed each other, the comb gains more electrons, so it is negatively charged. The hair lost electrons so it is positively charged. 6. When the comb is close to the tissue paper, why is it attracted into the comb? The tissue paper is attracted into the comb because the comb gains more electrons. It is negatively charged. 9. After some time, why does it fall again? Because the electron at the comb is transferred to the tissue and will neutral again.

Rubbing materials does NOT create electric charges. It just transfers electrons from one material to the other.

Where do charges come from?

When a balloon rubs a piece of wool...

electrons are pulled from + the wool to the balloon. – + – The balloon has more + – electrons than usual. – + – + The balloon : – charged wool + –

The wool

: + charged

Electric Charge The Transfer of Charge SILK

Glass Rod

Glass and silk are insulators: charges stuck on them stay

Electric Charge The Transfer of Charge

- -

+ + +

SILK

-

Glass Rod

In rubbing process, the negative charge will move from glass rod to silk.

Electric Charge The Transfer of Charge + + - + + +

SILK

Glass Rod

1. After rubbing process so, silk gains more electrons (negatively charged ) from glass rod. 2. The glass rod loses electrons (positively

Electric Charge

+

+

Two positively charged rods repulse each other.

Electro-negativity

Relative electro-negativity ranking for some common materials from electron donating materials (+, glass) to electron accepting materials (-, teflon)

+ + + + + + -

+++ +++ ++ +

-------

 Glass  Human Hair  Nylon  Silk  Fur  Aluminum  Paper  Cotton  Copper  Rubber  PVC  Teflon

SO, IF TWO ELECTRIC CHARGED OBJECTS CLOSER, THERE ARE TWO POSSIBILITY :

Test A balloon has a negative charge when rubbed by a woollen cloth. 1

If the balloon can attract some paper scraps, which of the following cannot be the charge of paper scraps? A

Neutral

C

Negative

B Positive

A balloon has a negative charge when rubbed by woollen cloth.

2

During rubbing, what have been transferred between the woollen cloth and the balloon? A

Electrons

C

Neutrons

B Protons

How does a positively charged rod attract a neutral object? When a + charged rod is put near neutral object, ______________ is induced on the side of the object near the rod and _____________ is induced on the side away from the rod. The rod can attract the netural object because _________ between rod and – induced charge > the ________ between rod and + induced charge.

Thanks

How does a positively charged rod attract a neutral object? When a + charged rod is put near neutral object, negative charge is induced on the side of the object ______________ near the rod and _____________ positive charge is induced on the side away from the rod. The rod can attract the netural object because _________ attraction between rod and – induced charge > the ________ repulsion between rod and + induced charge.