chapter 32 notes i
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Chapter 32 Notes I. Electrical Charge- Electrostatics. What does it mean if something has a charge?. Charges are physical properties of matter. What is a static charge?. charges at rest. - PowerPoint PPT PresentationTRANSCRIPT
Chapter 32 Notes I
Electrical Charge- Electrostatics
What does it mean if something has a charge?
Charges are physical properties of matter
What is a static charge?
charges at rest. Electrical forces are much stronger than gravity
but the repel each other, however they are still acting on you at all times.
Can be positive and negative. Mythbusters vandegraff
Like charges repel and unlike charges attract. Neutrals are attracted to all charged objects. Charges exert a force through a distance. The two charges are considered to be opposite,
because an object with equal amounts of positive and negative charge has no net charge.
Electrical Forces are much stronger than gravity…
Why don’t we notice them?
The attractive and repulsive forces between the charges in Earth and the charges in your body balance out!!!!
Charge and the Atom
What 3 subatomic particles are the atom made of?
What is the charge of each?
Electromagnetic force is significant at atomic level. Things you know:Atom has positively charged nucleus
surrounded by negatively charged electrons
All electrons are identical (same mass; same quantity of negative charge)
All protons are identical (same mass; same quantity of positive charge)
Nucleus composed of protons and neutrons. Neutrons are neutral
Neutral atoms have equal protons and electrons so zero net charge
Reviewing what you already know…
Do metals tend to gain or lose electrons? Lose Do atoms lose or gain protons? no What is an atom called that does not have
equal numbers of protons and electrons? ion If electrons are in excess the net charge is? Negative If protons are in excess the net charge is? positive
Conservation of Charge The total amount of charge in the universe is
constant Charges cannot be created or destroyed – only
transferred. Electrons cannot be created or destroyed – only
transferred.
Conductors Materials through which electric charge
can flow Outer electrons are loose METALS, water, human body, salts Head rush Human conductors
INSULATORS Electrons are tightly bound and
remain with particular atoms. – not free to wander
Poor conductors of electricity RUBBER, GLASS, styrofoam, paper
Random question… Does lightening ever strike the same
place twice?
SemiconductorsA third class of materials that
have electrical properties in between insulators and conductors.
Germanium and siliconSometimes act as insulators and
sometimes as conductors
Transferring Charges Electric charges can be transferred by
1. Friction2. Contact3. Induction
Charge by Friction Transfer of electrons between two
objects that are touching. Electrons will travel to the object that
has the higher electron affinity (love for electrons)
Charge by Contact Both insulators and conductors can be
charged by contact. Contact occurs between charged object
and neutral object. These two objects will then have the same charge.
Involves transfer of electrons
Charge by Induction If a charged object is brought near a
conducting surface, even WITHOUT physical contact, electrons will move to the conducting surface.
Involves rearrangement of electrons
Charging by induction occurs during thunderstorms. The negatively charged bottoms of clouds induce a positive charge on the surface of Earth below. Most lightning is an electrical discharge between oppositely charged parts of clouds. The kind of lightning we are most familiar with is the electrical discharge between clouds and oppositely charged ground below.
Grounding When we allow charges to move off (or
onto) a conductor by touching it, it is common to say it is grounded.
Charge by Induction If this source is connected to the earth
by conducting wire or pipe (grounded), the electrons will move into or out of the substance.
1. If a neutral atom has 22 protons in its nucleus, the number of surrounding electrons is
a. less than 22.b. 22.c. more than 22.d. unknown.
Assessment Questions
1. If a neutral atom has 22 protons in its nucleus, the number of surrounding electrons is
a. less than 22.b. 22.c. more than 22.d. unknown.
Answer: B
Assessment Questions
2. When we say charge is conserved, we mean that charge can a. be saved, like money in a bank.b. only be transferred from one place to another.c. take equivalent forms.d. be created or destroyed, as in nuclear reactions.
Assessment Questions
2. When we say charge is conserved, we mean that charge can a. be saved, like money in a bank.b. only be transferred from one place to another.c. take equivalent forms.d. be created or destroyed, as in nuclear reactions.
Answer: B
Assessment Questions
4. Which is the predominant carrier of charge in copper wire? a. protonsb. electronsc. ionsd. neutrons
Assessment Questions
4. Which is the predominant carrier of charge in copper wire? a. protonsb. electronsc. ionsd. neutrons
Answer: B
Assessment Questions
5. When you scuff electrons off a rug with your shoes, your shoes are then a. negatively charged.b. positively charged.c. ionic.d. electrically neutral.
Assessment Questions
5. When you scuff electrons off a rug with your shoes, your shoes are then a. negatively charged.b. positively charged.c. ionic.d. electrically neutral.
Answer: A
Assessment Questions
6. When a cloud that is negatively charged on its bottom and positively charged on its top moves over the ground below, the ground acquires a. a negative charge.b. a positive charge.c. no charge since the cloud is electrically neutral.d. an electrically grounded state.
Assessment Questions
6. When a cloud that is negatively charged on its bottom and positively charged on its top moves over the ground below, the ground acquires a. a negative charge.b. a positive charge.c. no charge since the cloud is electrically neutral.d. an electrically grounded state.
Answer: B
Assessment Questions
7. When a negatively charged balloon is placed against a non-conducting wall, positive charges in the wall area. attracted to the balloon.b. repelled from the balloon.c. too bound to negative charges in the wall to have any effect.d. neutralized.
Assessment Questions
7. When a negatively charged balloon is placed against a non-conducting wall, positive charges in the wall area. attracted to the balloon.b. repelled from the balloon.c. too bound to negative charges in the wall to have any effect.d. neutralized.
Answer: A
Assessment Questions