Not moving or stationary Static Electricity These notes will be on Mr. L s website for your studying enjoyment!!! Lyzinski Physics
Some very simple rules There are only two types of charge: POSITIVE AND NEGATIVE (electrons have negative charges and protons have positive charges). Objects that have the same amount of and charge are called NEUTRAL. Like charges repel. Opposite charges attract. Neutrally charged Positively charged Negatively charged
The atom Nucleus (protons, neutrons) Electrons Orbit in clouds Occupy levels Protons do NOT get transferred from atom to atom!!! Gain energy and jump up, lose energy and jump down. Held in orbit by the proton attraction (in other words, electric attraction between & supplies F C ) Some atoms hold their electrons better than others. Electrons held weakly can become lost (freeelectrons) or get stolen by another atom.
So, what happens when two atoms come into contact with each other??? (A little comic will help us understand this )
Act 1: Two neutral atoms meet I like my electrons, but not too much! The only thing in the world I care about is electrons. I ll even steal to get more. e p e p e p Neutral p Atom #1 e e p p e p e e p p Neutral Atom #2 p e e e p Holds onto its electrons with a weak force Holds onto its electrons with a strong force
Act 2: The atoms touch Oh.Pardon me. Outta my way. freak!!! e p e p e p Neutral Atom #1 p e e p e p e p e p p Neutral Atom #2 p e e e p
Act 3: The atoms go their separate ways He seemed like such a nice guy Sucker!!!!! Ha Ha Ha!!!! p p NOW a p p positive atom e Loses electrons, thus becoming more positive p p e e e p p e e e e e NOW a negative p p atom p e e Gained electrons, thus becoming even more negative (scary thought)
Lose Electrons When objects rub together, one object might acquire electrons and some might lose them. Objects that lose their atoms exert weaker forces of attraction on their electrons than the other objects do. These other objects, with the stronger forces of attraction, steal the electrons away. So. how do we know which gets more electrons??? We look at the electrostatic series table. The material closer to the top loses electrons. Gain Electrons Air Human Hands, Skin Rabbit Fur Glass Human Hair Nylon Wool Silk Aluminum Paper Cotton Wood Lucite Rubber Balloon Hard Rubber Copper Polyester Polystyrene Acrylic Polyurethane Silicon
The further apart two materials are on the electrostatic series chart, the more electrons get transferred. Example: Rub wool against wood.. and wood gains electrons ( a few) an becomes negatively charged. Example: Rub wool against polyurethane. and wool loses electrons (a lot) and becomes positively charged. Air Human Hands, Skin Rabbit Fur Glass Human Hair Nylon Wool Silk Aluminum Paper Cotton Wood Lucite Rubber Balloon Hard Rubber Copper Polyester Polystyrene Acrylic Polyurethane Silicon
So how do you charge an object By FRICTION (rubbing two materials together) By CONTACT By INDUCTION By POLARIZATION
#1 Charging by Friction Rub two objects together. One will lose electrons (becoming positive) and one will gain electrons (becoming negative).
#2 Charging by Contact Touch an a charged object to another object. Then other object will receive the same charge as the charged fail. Positively Charged Neutrally Charged Positively Charged
Before learning about the 3 rd Charging Method, we need to learn about two types of materials. Conductors vs. Insulators
Allow charge to move freely Conductors vs. Insulators Do NOT allow charge to move freely Charged object, being brought close Metal Rod Electrons are free to move from one end to the other Light, conducting sphere beaker Glass Rod Electrons can t move freely. They remain at the touched end
One more thing before learning about the 3 rd Charging Method. We need to learn about.charge Separation When a charged object is brought near (but not touching) a neutral conductor, the charged object causes the charge on the conductor to separate. No touchy!!! Charges are equally spread out. Charges have been separated.
#3 Charging by Induction Step 1 Bring a charged object close to (BUT NOT TOUCHING) a neutral conductor. Step 2 The electrons will move (causing a charge separation). Step 3 Make the separation permanent (while keeping the charged object close, but not touching). Step 4 Remove the charged object, leaving a newly charged object with THE OPPOSITE CHARGE.
An Example of Charging by Induction Initially uncharged object Insulated STEP #1 stand STEP #2 Close. but not quite touching No touchy!!! STEP #3 Grounding (or allowing electrons to jump onto the human body, which is normally neutral) Move it away (after removing hand first) STEP #4 End result..charged object
Another Example of Charging by Induction 2 neutral bars touching Bring a charged object close charges separate Move the blocks apart (with an insulator) Result: two oppositely charged bars
A strange phenomena: A neutral object being attracting to a charged object!!! Negatively charged object and neutral object Bring objects close (not touching) and charges separate The neutral ball (still neutral, just separated) attracts to the negative one!!!!!!
#4 Charging by Polarization Positively charged object Plastic comb Can you induce charge on an insulator??? After being charged, the comb can induce a charge on little paper strips and attract them. Electrons are not free to move in the insulator. However, the positive and negative charges do become POLARIZED, aligning themselves to the charged object. A force of attraction is induced, but it is WEAK!
In conclusion: There are 4 ways to charge objects (friction, contact, induction, polarization). Only electrons move and can be transferred (protons and neutrons are never transferred). Electrons can only move in conductors. Charging by contact results in two SIMILARLY charged objects. Charging by induction results in two OPPOSITELY charged objects (and requires a conductor). Charging by polarization requires an insulator.