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Intro to Electrostatics.notebook
1
December 22, 2011
Feb 94:04 PM
Everything is made of atoms!
...what's an atom?
• Comes from greek word, meaning unbreakable• Was thought to be the smallest unit of matter.• Now is seen as the smallest unit of an element.
BUT......
Apr 1810:55 AM
Subatomic Particles
• Names
• Location
• Charges
• Mass
• Size why is it difficult to get pictures?
or
http://learn.genetics.utah.edu/content/begin/cells/scale/
Apr 1811:25 AM
Name Location Charge Mass
Proton Nucleus Positive (+) 1 amu
Neutron Nucleus Neutral 1 amu
Electron Orbital Negative () Negligible
Subatomic Particles
1 amu = 1.6 x 1027 kg??
1 proton = 1836 electrons in terms of mass??
Intro to Electrostatics.notebook
2
December 22, 2011
Apr 198:56 PM
Atoms are neutral because they contain the same number of positive and negative charges. An atom that gains or loses electrons is called an ion, and is either positively (cation) or negatively (anion) charged.
Ions
May 37:50 PM
1. Matter is made of atoms
2. Atoms can gain and lose electrons. But NOT Protons.
3. Some atoms (and molecules) have a strongerhold on their electrons than others.
Some things we ought to know about matter
PROTONS CAN'T BE GAINED OR LOSTONLY ELECTRONS
May 38:06 PM
1. Matter is made of atoms (and molecules)
Intro to Electrostatics.notebook
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December 22, 2011
May 38:12 PM
2. Atoms (and molecules) can gain and lose electrons. But NOT Protons.
PROTONS STAY IN THE NUCLEUSALERT
May 38:12 PM
3. Some atoms (and molecules) have a strongerhold on their electrons than others.
VS
FIGHT!
Feb 118:13 AM
Intro to Electrostatics.notebook
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December 22, 2011
May 38:15 PM
Insulators and Conductors
• Insulators are materials whose atoms have tightly bound electrons. These electrons are not free to roam around and be shared by neighboring atoms.
Example: Nonmetal elements, glass, rubber, plastic, pure water
• Conductors are materials whose atoms have less tightly bound electrons. These electrons are able to be moved through and shared with neighboring atoms
Example: Metal elements, dirty water
May 37:58 PM
Electric charges can be either positive or negative.
Like (the same) charges repel and unlike (different) charges attract.
This is known as the Law of Electric Charges.
The movement of electrons generates charges
May 38:28 PM
Because the electric charge on an object will often remain for long periods of time, the electricity is called static electricity (stationary).
The science of studying static electricity is called electrostatics
Objects Stay Charged
Intro to Electrostatics.notebook
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December 22, 2011
May 37:52 PM
• If an object has no electric charge, it is said to be neutral.
• Two electrically uncharged objects will have no effect on each other.
What about an electrically charged object and a neutral object? Will anything happen?
May 37:57 PM
YES!
An electrically charged object exerts a force on a neutral object, even if they are not touching!
May 38:15 PM
To determine whether or not charge has been transferred, a device called an electroscope can be used.
This will respond to charged objects but not to uncharged objects.
The evidence!
Intro to Electrostatics.notebook
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December 22, 2011
May 38:33 PM
May 38:33 PM
May 38:33 PM
Intro to Electrostatics.notebook
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December 22, 2011
May 38:33 PM
May 38:34 PM
May 38:34 PM
Draw a series of diagrams to show what will happen with a positively charged rod.
Intro to Electrostatics.notebook
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December 22, 2011
May 47:55 PM
The Three Methods of Charging
• Friction
• Contact
• Induction
May 47:56 PM
Friction
When two substances are rubbed together:
• the substance with a weaker hold on its electrons will lose some of its electrons (will become +ve).• the substance with a stronger hold on its electrons will gain some electrons (become ve)
When charging by friction, both substances start off neutral. One becomes positive, and the other negative.
May 48:00 PM
+ ++ +
+
Friction
++ +++
Intro to Electrostatics.notebook
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December 22, 2011
May 48:02 PM
The Electrostatic Series
A list of common materials was made that puts items in order from weakest hold of electrons to strongest hold.
What would happen if you rubbed silk on brass?
May 48:10 PM
Contact
When a charged object comes in contact with a neutral object, electrons move from the object with more to the object with less.
This often creates a SPARK!
When charging by contact, both objects end up with the same charge
May 48:14 PM
Draw diagrams to show what happens when a positively charged rod makes contact with a neutral pithball.
Intro to Electrostatics.notebook
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December 22, 2011
May 48:16 PM
May 48:18 PM
Family Guy!!!
May 48:19 PM
Induction
If a negatively charged rod is brought near an neutral object, the electrons in the neutral object will be repelled.
the side of the neutral object near the negatively charged rod will become positively charged and will be attracted.
Intro to Electrostatics.notebook
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December 22, 2011
May 48:21 PM
Grounding
If the neutral pith ball is touched on its negative side using another neutral object or wire (called a ground), the electrons will move over to the new object, leaving the pith ball positively charged.
Notice that the negative rod never touched the pith ball!
We have given a pith ball a positive charge using a negatively charged rod.
May 48:23 PM
Draw a series of diagrams to show how to charge a pith ball negatively using a positively charged rod.
May 67:57 AM
• TVO Videos: Charging and Induction• Cut and Paste Assignment
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