Static Electricity blog contains
What Is Static Electricity?
Where do charges come from?
Insulators and conductors
Static Discharge
Grounding
What Is Static Electricity?
A stationary electrical charge that is built up on the surface of a material
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.
Where do charges come from?
Matter is made up of atoms.
+ Proton (positive charge)
o neutron (neutral)
- electron (negative charge)
If electrons = protons substance became neutral
If electrons > protons substance became gaining electrons, negative charge
If electrons < protons substance became losing electrons, positive charge
Relative electro-negativity ranking for some common materials from electron donating materials (+, glass) to electron accepting materials (-, teflon)
Rubbing materials does NOT create electric charges. It just transfers electrons from one material to the other.
When a balloon rubs a piece of wool electrons are pulled from the wool to the balloon.
The balloon: – charged,
The wool: +charged
Insulators and conductors
Insulators: materials that do NOT allow electrons to flow through them easily.
Insulators can be easily charged by friction as the extra electrons gained CANNOT easily escape.
Conductors: materials that allow electrons to flow through them easily.
Conductors CANNOT be easily charged by friction as the extra electrons gained can easily escape.
Induction: The production of a charge in an uncharged body by bringing a charged object close to it
When negatively charged rod is put near a metal can...
electrons of the can are pushed away from the rod.
Top of the can: positive
Bottom of the can: negative
Attraction > repulsion
Attraction of uncharged objects
Similarly, when charged rod is close to paper scrap molecules of paper align.
Here attraction between the rod and + charge > repulsion between the rod and - charge.
Static Discharge
Human body can not feel less than 2,000 volts of static discharge
Static charge built up by scuffing shoes on a carpet can exceed 20,000 volts?
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.
Grounding
An object is grounded when it is connected to the earth through a connecting wire.
If a charged conductor is grounded, it will become neutral.