Today we made our pennies into electromagnets! Not as cool as it sounds, I know, but still neat to see that any conductor may act like a magnet when a magnetic field nearby is moved or strengthened/weakened - relates to tonight's homework about the current in a generator when a magnet is not moving next to it.... this is zero; the magnet and coil of wire must move relative to one another for the coil to have induced electric current.
After the pennies were moved with moving magnets, we experimented with Iron (Fe) filings and magnets, watched some cool laserdisc videos, and made some cool DC motors with a magnet, a nail, a battery, and a piece of wire (show your family!) You can change the direction it moves in two ways.... ?
Wednesday, January 30, 2013
Tuesday, January 29, 2013
Class activities, HMWK for Thursday
Yesterday we worked with attraction and repulsion of magnets and finding magnetic and nonmagnetic materials (informally everyone did!), answered questions on homework that was handed back, worked with Earth's magnetic field, compasses, and balanced magnets, and had notes on magnetism.
Today we finished notes about electromagnetism (see previous posts for the link to all notes) and saw how compasses react to current-carrying wires. At the end of class students got a chance to interfere with moving electrons in a CRT monitor and make magnet-launchers with coils of current carrying wire.
Tomorrow we'll make motors (bring your magnets and a spare AAA, AA, C, or D cell battery), watch some laserdisc videos about magnetism and electromagnetism, and start exploring magnetic fields with iron filings.
Homework due Thursday: Read p. 438-444, p. 444#1-6
Start reviewing for electricity and magnetism exam, slated for next Wednesday. We will likely have a lab on Monday using electromagnets.
Today we finished notes about electromagnetism (see previous posts for the link to all notes) and saw how compasses react to current-carrying wires. At the end of class students got a chance to interfere with moving electrons in a CRT monitor and make magnet-launchers with coils of current carrying wire.
Tomorrow we'll make motors (bring your magnets and a spare AAA, AA, C, or D cell battery), watch some laserdisc videos about magnetism and electromagnetism, and start exploring magnetic fields with iron filings.
Homework due Thursday: Read p. 438-444, p. 444#1-6
Start reviewing for electricity and magnetism exam, slated for next Wednesday. We will likely have a lab on Monday using electromagnets.
Friday, January 25, 2013
HMWK for Tuesday
Today we went over a couple of answers on homework that was turned in today, finished a video about AC and DC, electric power generation and transmission (and the history of it) and started notes on Magnetism (see Thursday's post for a link to notes).
HMWK due Tuesday: Read p. 431-437; p. 437#1-5
Also make sure to bring $1 for some magnets on Monday. If you truly can't afford them please see me, otherwise I might have a couple of broken ones to loan to you.
If you already have magnets, remember to bring them all next week for use in class!!!!
HMWK due Tuesday: Read p. 431-437; p. 437#1-5
Also make sure to bring $1 for some magnets on Monday. If you truly can't afford them please see me, otherwise I might have a couple of broken ones to loan to you.
If you already have magnets, remember to bring them all next week for use in class!!!!
Thursday, January 24, 2013
Electric Current / Power Quiz, HMWK for Friday
Due Friday: read 424-430, p. 430#3-7
Today we had a quiz about electric current and power, went over answers to homework about electric power, and started a video about alternating and direct current.
Friday we will finish the video and go over answers on the homework (hopefully) and start notes on Magnetism!
Today we had a quiz about electric current and power, went over answers to homework about electric power, and started a video about alternating and direct current.
Friday we will finish the video and go over answers on the homework (hopefully) and start notes on Magnetism!
Wednesday, January 23, 2013
Tuesday, January 15, 2013
Circuits Notes, Ohm's Law Lab, Friday HMWK, magnets?
Circuits notes from today
Ohm's Law Lab handout from today
We also drew circuit diagrams and calculated total resistance and current for several different circuits, as well as saw light bulbs with different resistances (wattages) and what happens when they're connected in series with like and different bulbs.
The Ohm's Law lab will be due on Monday.
Tomorrow (Wed) I will teach classes more about using meters to measure voltage, current, and resistance, and we will start our lab (should finish on Thursday).
The first few minutes of Thursday, Mrs. Greene will review answers / solutions to the algebra review quiz and discuss expectations for Honors Chemistry. Bring questions and be ready to go fast!
Homework (due Friday): READ p. 407-413. P. 411#1-3, p. 412#1-2, and p. 413#1-8
We will have a quiz on topics of electricity - electrostatics and electric current - on Tuesday. We will also be starting studies in magnetism and electromagnetism next week. At some point I will be selling batteries (I buy them in bulk) if you would like to have some to experiment with and keep. They are 3 for $1, or 10 for $3 - I don't give out the school provided batteries to students anymore - due to theft and breakage, we have very few and I don't want to limit your studies because I'm trying to be over-vigilant about people stealing/breaking the school's property.
If you are messing with your magnets in another class, they will be confiscated permanently by that other teacher. Don't make it a problem - please don't prevent me from teaching about magnetism in the future.
Ohm's Law Lab handout from today
We also drew circuit diagrams and calculated total resistance and current for several different circuits, as well as saw light bulbs with different resistances (wattages) and what happens when they're connected in series with like and different bulbs.
The Ohm's Law lab will be due on Monday.
Tomorrow (Wed) I will teach classes more about using meters to measure voltage, current, and resistance, and we will start our lab (should finish on Thursday).
The first few minutes of Thursday, Mrs. Greene will review answers / solutions to the algebra review quiz and discuss expectations for Honors Chemistry. Bring questions and be ready to go fast!
Homework (due Friday): READ p. 407-413. P. 411#1-3, p. 412#1-2, and p. 413#1-8
We will have a quiz on topics of electricity - electrostatics and electric current - on Tuesday. We will also be starting studies in magnetism and electromagnetism next week. At some point I will be selling batteries (I buy them in bulk) if you would like to have some to experiment with and keep. They are 3 for $1, or 10 for $3 - I don't give out the school provided batteries to students anymore - due to theft and breakage, we have very few and I don't want to limit your studies because I'm trying to be over-vigilant about people stealing/breaking the school's property.
If you are messing with your magnets in another class, they will be confiscated permanently by that other teacher. Don't make it a problem - please don't prevent me from teaching about magnetism in the future.
Monday, January 14, 2013
Simple Circuits, Wed Hmwk
Today classes got to experiment with some simple DC circuits and tiny incandescent Christmas light bulbs, after discussing how we pay for electricity (kilowatt - hours (kWh)) and finding out how to go from knowing an appliance's wattage to finding how much we pay at about 10 cents per kWh.
Some other announcements:
Mrs. Greene will visit Thursday to give out answers to algebra review quizzes (you and parents register for classes Thursday night (Connect?))
The bonus problem in the notes: what happens to an appliance's power when you double its voltage, as if you took a 120V appliance (U.S.A.) to another country outside North America?
Current within it doubles, and since current is then multiplied by double the voltage, the power of the device quadruples!!!
This is why electric lines transmitting huge amounts of electricity use higher voltage - resistance becomes insignificant as voltage is increased, because a huge amount of current is not needed to deliver lots of energy as long as that energy is at a high potential (voltage).
This is also why the rest of the world operates at a much more efficient 120V, and why we in the U.S.A. don't just use an even lower voltage (like 12V or less) to deliver energy to our homes. It would be safe for anyone to touch, but resistance would be a huge factor and make any significant transmission distance impossible.
Optional assignment that was assigned on Friday is due Jan 25th. See Friday's post.
HMWK for Tuesday: see Friday's post.
Some other announcements:
Mrs. Greene will visit Thursday to give out answers to algebra review quizzes (you and parents register for classes Thursday night (Connect?))
The bonus problem in the notes: what happens to an appliance's power when you double its voltage, as if you took a 120V appliance (U.S.A.) to another country outside North America?
Current within it doubles, and since current is then multiplied by double the voltage, the power of the device quadruples!!!
This is why electric lines transmitting huge amounts of electricity use higher voltage - resistance becomes insignificant as voltage is increased, because a huge amount of current is not needed to deliver lots of energy as long as that energy is at a high potential (voltage).
This is also why the rest of the world operates at a much more efficient 120V, and why we in the U.S.A. don't just use an even lower voltage (like 12V or less) to deliver energy to our homes. It would be safe for anyone to touch, but resistance would be a huge factor and make any significant transmission distance impossible.
Optional assignment that was assigned on Friday is due Jan 25th. See Friday's post.
HMWK for Tuesday: see Friday's post.
Friday, January 11, 2013
Tuesday hmwk, notes on Power, Optional Assignment
Notes from today on electric power
Homework due Tuesday: p. 884#138-140, 148 AND p. 420#1-4,13
Bring lab journals Tuesday and Wed!
First 2013 optional assignment:
Find (or calculate using the information you can find) values for the following categories of FIVE items in your home:
Item name Voltage Power Current Resistance Cost to run 1 month (assume $.09 /kWh)
(like TV) (usually 120v ex. 3 hours/day *30 days * wattage in kW
unless plugged into *9 cents per kWh
a transformer at the wall)
Due no later than Friday, Jan 25
Homework due Tuesday: p. 884#138-140, 148 AND p. 420#1-4,13
Bring lab journals Tuesday and Wed!
First 2013 optional assignment:
Find (or calculate using the information you can find) values for the following categories of FIVE items in your home:
Item name Voltage Power Current Resistance Cost to run 1 month (assume $.09 /kWh)
(like TV) (usually 120v ex. 3 hours/day *30 days * wattage in kW
unless plugged into *9 cents per kWh
a transformer at the wall)
Due no later than Friday, Jan 25
Thursday, January 10, 2013
Quiz Friday, notes...
Notes for today:
https://docs.google.com/presentation/d/1YzgqYEDwx0p76yPAAChaJNJu8XDxx1y_HWJ1cX5AJvs/edit
Electrostatics Quiz Friday - here's a review.
https://docs.google.com/presentation/d/1YzgqYEDwx0p76yPAAChaJNJu8XDxx1y_HWJ1cX5AJvs/edit
Electrostatics Quiz Friday - here's a review.
Monday, January 7, 2013
1-7-13: Metals/Nonmetals, Gounding/Insulation, HMWK for Wed
HMWK for Wed: Read p .400-405, p. 405#1-7
Today we had a warm up: Your blanket takes some e- from you. You are now ____ and your blanket is now ___.
Notes: Metals vs Nonmetals and Grounding vs. Insulating:
Metals and Nonmetals vary mainly based on how they treat their electrons.
Metals have relatively few p+ in the nucleus, and can't hold e- very tightly/closely. This makes their e- free to come and go, and also makes metals relatively big atoms. The loose grip on e- makes metals good conductors.
Nonmetals have larger numbers of p+ in the nucleus and hold e- more tightly. This means smaller atoms and electrons that are not able to move very freely. This makes nonmetals generally good insulators.
Grounding is when an object is connected to the Earth by a conductor. The round plug in a 3-prong electrical outlet is the "ground" and is connected to a home's copper plumbing, and... the Earth. This grounding has multiple reasons; motorized electronics, if there is a short or a static electrical discharge, dissipate this electricity to the Earth and not a person. Second, a person touching a computer, etc. won't cause the internals to get damaged because they're sealed inside a grounded metal cage.
Insulating is kind of opposite from grounding... not exactly. Insulating is keeping an object from contact with other conductors (or the Earth). It's accomplished with nonmetals; plastics, rubber, AIR, etc. Insulators CAN allow e- to move, just not as easily as metals do. The more push the e- have (voltage), the more likely e- are to move. Your skin is a good enough insulator to hold a 1.5V battery in your hand, but it's not really safe to go grabbing 120V or 240V wires; they will conduct through you!
We will review insulation with the Van de Graff generator; 500kV will jump through your shoes and into the floor like they weren't there. :)
Other stuff from today: Ranking tasks WS relating electric force between particles with different charge and spacing (see me for a copy) and induced charges.
Video and demonstrations on the Wimshurst Electrostatic Generator.
Tomorrow (Tues) we will have an algebra quiz to help you decide whether to take Honors chemistry or regular Chemistry next year (signups are soon!) , we will have some brief notes regarding how charges behave on conductors, and demonstrations (some hands-on!) with the Van de Graff electrostatic generator.
Notes on charge distribution: Charge spreads over the surface of conductors; the electric field inside a conductor is zero. If you've ever tried to use a cell phone in an elevator or metal building (seckman HS), you have experienced this!
On the surface, charges repel each other and tend to spread out over the surface. For a spherical object, each charge pushes on the others with equal force and there is little net force on each charge (the larger the sphere, the closer this net force gets to zero)
With a pointed object, charges close to the point are repelled by others away from the point unevenly; they have nothing pushing them back, so they experience a net force pushing them off the object. For this reason, you are more likely to receive a shock when approaching a doorknob with your finger than a whole hand; charges accumulate and push toward the point.
This idea is manipulated with lightning rods; pointed rods that protect buildings from lightning. Charges accumulate on the points and make strikes less likely to hit other objects.... at the same time, charge "leaks off" the rods, making lightning less likely in the first place.
We experienced charging by induction and contact with the Van de Graff generator and got to play with rounded vs. pointed approaches for lightning rods a bit. Wednesday we'll have more; an insulated platform for those who don't want to feel any shock but would like to be charged!
Today we had a warm up: Your blanket takes some e- from you. You are now ____ and your blanket is now ___.
Notes: Metals vs Nonmetals and Grounding vs. Insulating:
Metals and Nonmetals vary mainly based on how they treat their electrons.
Metals have relatively few p+ in the nucleus, and can't hold e- very tightly/closely. This makes their e- free to come and go, and also makes metals relatively big atoms. The loose grip on e- makes metals good conductors.
Nonmetals have larger numbers of p+ in the nucleus and hold e- more tightly. This means smaller atoms and electrons that are not able to move very freely. This makes nonmetals generally good insulators.
Grounding is when an object is connected to the Earth by a conductor. The round plug in a 3-prong electrical outlet is the "ground" and is connected to a home's copper plumbing, and... the Earth. This grounding has multiple reasons; motorized electronics, if there is a short or a static electrical discharge, dissipate this electricity to the Earth and not a person. Second, a person touching a computer, etc. won't cause the internals to get damaged because they're sealed inside a grounded metal cage.
Insulating is kind of opposite from grounding... not exactly. Insulating is keeping an object from contact with other conductors (or the Earth). It's accomplished with nonmetals; plastics, rubber, AIR, etc. Insulators CAN allow e- to move, just not as easily as metals do. The more push the e- have (voltage), the more likely e- are to move. Your skin is a good enough insulator to hold a 1.5V battery in your hand, but it's not really safe to go grabbing 120V or 240V wires; they will conduct through you!
We will review insulation with the Van de Graff generator; 500kV will jump through your shoes and into the floor like they weren't there. :)
Other stuff from today: Ranking tasks WS relating electric force between particles with different charge and spacing (see me for a copy) and induced charges.
Video and demonstrations on the Wimshurst Electrostatic Generator.
Tomorrow (Tues) we will have an algebra quiz to help you decide whether to take Honors chemistry or regular Chemistry next year (signups are soon!) , we will have some brief notes regarding how charges behave on conductors, and demonstrations (some hands-on!) with the Van de Graff electrostatic generator.
Notes on charge distribution: Charge spreads over the surface of conductors; the electric field inside a conductor is zero. If you've ever tried to use a cell phone in an elevator or metal building (seckman HS), you have experienced this!
On the surface, charges repel each other and tend to spread out over the surface. For a spherical object, each charge pushes on the others with equal force and there is little net force on each charge (the larger the sphere, the closer this net force gets to zero)
With a pointed object, charges close to the point are repelled by others away from the point unevenly; they have nothing pushing them back, so they experience a net force pushing them off the object. For this reason, you are more likely to receive a shock when approaching a doorknob with your finger than a whole hand; charges accumulate and push toward the point.
This idea is manipulated with lightning rods; pointed rods that protect buildings from lightning. Charges accumulate on the points and make strikes less likely to hit other objects.... at the same time, charge "leaks off" the rods, making lightning less likely in the first place.
We experienced charging by induction and contact with the Van de Graff generator and got to play with rounded vs. pointed approaches for lightning rods a bit. Wednesday we'll have more; an insulated platform for those who don't want to feel any shock but would like to be charged!
Friday, January 4, 2013
1-4-13: Induction
Notes from today and yesterday combined here
Today we reviewed the phenomena we experienced yesterday; specifically being able to influence a neutral object by bringing a charged object near but not even touching it. The reason for this: Induction - when the charges within a conductor move around as a result of another electric field.
Induction is only responsible for attraction, not repulsion, between two objects. Therefore if you see two items attract, it could be due to opposite charges OR induction of one object.
On the other hand, if you see repulsion, then you are sure the charges are the same.
We bent streams of water today and induced charges on aluminum cans and pith balls again, and discussed/diagrammed what we think is going on in each situation in the notes.
Finally, class ended with some time to explore and a demonstration of the Wimshurst induction generator. More with this guy next week!
HMWK for monday: read 392-399; p. 399#1-7. #7 is review - you can do it using your 1st semester knowledge!!!!!
Today we reviewed the phenomena we experienced yesterday; specifically being able to influence a neutral object by bringing a charged object near but not even touching it. The reason for this: Induction - when the charges within a conductor move around as a result of another electric field.
Induction is only responsible for attraction, not repulsion, between two objects. Therefore if you see two items attract, it could be due to opposite charges OR induction of one object.
On the other hand, if you see repulsion, then you are sure the charges are the same.
We bent streams of water today and induced charges on aluminum cans and pith balls again, and discussed/diagrammed what we think is going on in each situation in the notes.
Finally, class ended with some time to explore and a demonstration of the Wimshurst induction generator. More with this guy next week!
HMWK for monday: read 392-399; p. 399#1-7. #7 is review - you can do it using your 1st semester knowledge!!!!!
Thursday, January 3, 2013
1-3-13: Electric Charge
Today in class we had notes/discussion on atomic basics (some review), charging, and conservation of electric charge.
Notes from today here
We also had an activity / demonstrations with electroscopes and charging rods and induction of styrofoam balls with metallic paint.
HMWK due Monday: Read p. 392-399, p. 399#1-7
Notes from today here
We also had an activity / demonstrations with electroscopes and charging rods and induction of styrofoam balls with metallic paint.
HMWK due Monday: Read p. 392-399, p. 399#1-7
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