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SMTE 3315 Texas A & M University Electromagnetism MCQs

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Full Question

Electrical Charge
Objects are typically neutral but can become charged ( or + )
To charge means to TRANSFER electrons
If giving away electrons à Positive Charge
If taking on new electrons à Negative Charge
Electronegativity is the ability to retain electrons
Differs from material to material
More electronegative = holds electrons tighter
Chart on page 100
Least to most electronegative
Exercise 1 on Page 100
Remember, the more electronegative something is, the
more it will try to hold on to its electrons.
Remember from chemistry that protons are + and
electrons are –
Like charges repel while opposites attract
Charge ctd.
Inner electrons are attracted to nucleus more strongly
Outer electrons are easier to lose
Static Electricity
When an object is charged and the charge remains
there, static electricity is generated
Static means not-moving
Prefers dry conditions
Examples of Static Electricity
Gasoline pump accidents
Activity 4.1 on Page 102-103
Do not rub balloons in the hair on your head
Instead use your arm
Electrical Polarization
Instead of trading electrons, the electrons are
Remember, opposites attract
The electrons in neutral objects repel the electrons of
the charged balloon which leaves protons on the side
facing the charged balloon
Polarization Explanation
What is happening here?
The balloons and cans are negative after rubbing on
your arm
Small neutral objects are NOT getting charged because
you are not touching them
Charging vs. Polarization
Static Charging
Due to transfer of
Gain extra electrons = Loss of electrons = +
Results in two charged
Due to rearrangement
of the charges
Polarized object is
Charged object attracts
small, neutral but
polarized things
Polarization Activity
Hold a charged balloon (or can) over small strips of
tissue or foil. Try and get these to move without
touching them.
Static Electricity and Polarization
Electromagnetism Unit, Day 1
1. Yaaay! We survived the Chemistry unit. As I expected, the exam averages went up
significantly. So good job. I’m so sorry for the complications with the course, those
within and without of my control. It looks like now we will not be able to meet to turn
in the last two projects, so I am trying to decide what is best: alternate activities, or
optional/modified projects. I will let you know ASAP. Anyway, on to
Electromagnetism! A lot of today will feel like a review since many of our friends from
Chemistry make an appearance. There are a few labs, and if you have supplies to do
them at home, please do. If not, that’s okay. I will link to a video that shows most of
what we would do in lab.
2. Review! Just like in chemistry, we are still going to assume that everything is neutral
unless we say otherwise. They can become negative, or positive. In chemistry we
talked about negative and positive IONS, meaning one ion gained electrons (negative)
and one ion lost electrons (positive). Think like table salt, which was NaCl, or sodium
and chlorine. The sodium gives and electron (now positive!) to chlorine (now
negative!). The difference now is that we are talking about whole materials or things,
not just an ion. But still, if they lose electrons, they become positive. If they gain
electrons, they become negative.
3. Electromagnetism is how hard something holds onto its electrons. The more
electronegative something is, the tighter it holds onto them. In chemistry we talked
about specific elements and their electronegativity (which we used to subtract and
find out if a compound was ionic or covalent) but now we are actually talking about
whole materials and substances. The bulleted list on page 100 lists different
materials. The materials at the top are the most positive, meaning they will surrender
their electrons easier. Towards the bottom of the list, they are more likely to steal
electrons. So the very top (most positive) we have hands, but it says “usually too
moist.” Static electricity HATES humidity and moisture. You probably notice the
sensation of getting shocked/zapped when you touch things more in “Winter”
because the humidity tends to be lower. It is also more likely to happen inside when
there is an AC or heater on since both of those reduce humidity. Back to this list, it
doesn’t matter how far apart things are in the list, but if any 2 things are rubbed
together, whichever one is lower on the list will steal electrons (become negative)
from the object that is higher on the list (and that becomes positive).
4. For these questions, you are going to look at the list on page 100, and compare which
object is lower and which is higher on the list. Whichever one is higher on the list will
be positive when they are rubbed together. For instance, if we rubbed Aluminum and
Wood together, since Aluminum is higher on the list, it will be positive and the Wood
will be negative. Let’s pick a random number, and say the Wood will take 3 electrons
away from the Aluminum. That means the Wood has a charge of -3 and the Aluminum
has a charge of +3. In both cases, the total difference between protons and electrons is
3 which means the difference is the same (hint hint, you will need this for question 3).
5. Review! Keep in mind, protons are still positive, and electrons are negative. Also
please remember from chemistry that like charges will repel (ex: negative and
negative) while opposite charges will attract (ex: positive and negative). Just now that
we are in this unit, we are talking about whole materials, rather than elements or
polyatomic ions.
6. Review! Remember from atoms bonding, that electrons gather in layers or shells. We
are never going to do electron configuration again (the 1s22s2… stuff), but it is still
important to remember that the electrons fill from the inside out, and things will
always lose the outer electrons before losing the inner ones.
7. Static is literally a non-moving charge, which means a charge builds up and just stays
there, lurking, and waiting, to be discharged (when something new touches it). I’m
sure everyone has at one point been shocked/zapped when they touched another
person, a doorknob, something else. That was likely because you built up a static
charge. This will usually happen because you are dragging your feet on carpet, which
steals electrons. When you touch the doorknob (or whatever) the charge you built up
goes to neutralize out, which is why you feel the shock, or if it’s dark enough, you
might even see a spark.
8. Your clothes are so staticky when they come out of the dryer because static charges
form when things rub together in dry environments, and in a dryer clothes are
literally being tossed around in a DRY environment. Lightning is also a really big
example of a static charge. The air masses move around and build up charges that
discharge, violently, as lightning. If you have seen the movie Zoolander, you
understand how tragic gasoline pump fires can be, but what people don’t realize is
that they actually happen. Statistically, they happen not just in humid conditions, but
they are also more likely to happen to younger drivers. Any guesses why? (I would be
awkwardly drinking water and waiting at this point…). It is because when younger
drivers get out of a car, they just get out, but when older drivers get out, they kind of
have to pull themselves out. Basically to prevent this from happening, you should get
out of your car once to pump gas, touch something metal first (the door, the hood,
whatever) to get rid of any static charge you built up, and then pump gas. The reason
the gas pump fire would happen would be because you dragged your feet/bum on the
floor/seat of the car and built up a charge. If the next thing you touch is the actual gas
pump and there is a spark, it could ignite the gas fumes. In terms of blankets, I stayed
at my cousin’s house in Austin once, and during the winter she had the windows open
and the humidity was nearly zero. The blanket she gave me was one of those super
soft floofy ones. And in the night when I would move around, I could hear and see
sparks coming off it because it was building up static charges.
9. If you have a rubber balloon laying around, you can go ahead and easily do this with
that, but if you do not have a balloon, you can also use an empty soda/beer can it just
needs a little bit more charging than the balloon. When you do things like this in your
hypothetical future classroom, do not let students use the hair on their heads in case
anyone has lice and they share a balloon. Instead, carpet, sweaters, arm/leg hair, or
pet hair would work too if you are lucky enough to end up with a classroom pet. If
you are unable to do this activity (or just want a clear example, watch this video

10. We are shifting gears now to talk about electrical polarization. This is something
different. In Polarization, we are starting with something that is neutral, and
something that is charged. For instance, the neutral thing could be tiny scraps of foil
or tissue, or a slow stream of water. The neutral object would be something like a
charged balloon or charged can (both would be charged by rubbing on your hair). As
the charged balloon would come near the neutral object, the electrons in the neutral
object would rearrange.
11. Remember that like charges repel and opposites attract. When the negatively charged
balloon (meaning it has extra electrons) comes towards out neutral objects, the
electrons in the neutral object panic in terror! They are scared of (and repel) the
electrons in the charged object. The way they do this is to hide! They will hide on the
side of the neutral object that is not facing the charged object. This means they have
rearranged themselves and while the neutral object still has equal numbers of
protons and electrons, the side facing the charged object has all the protons, so it is
still neutral, but because the electrons are hiding, the side with all the protons is
attracted to the charged object.
12. This is a review slide that compares the differences between Static Charging, and
13. This is just a way to see polarization in action. If you do not have the supplies to do
this at home, that is very okay. You can see the same thing in the YouTube video at
the end of this section. The second half where he is using the stream of water is the
same thing as the foil. The neutral water molecules rearrange with the kinda sorta
negative Oxygen side hiding from the negatively charged object, and hiding behind
the kinda sorta positive Hydrogen side. If you watch the video and do not do this lab
at home, he demonstrates both this, and the reverse using a positively charged object,
in which case the hydrogen side hides behind the oxygen side. YouTube video:

Amps, Volts, and Ohms!
Electricity Unit – Day 2
1. Today we are talking about moving electricity, rather than static and polarization
from last time.
2. Electrical current, or electricity, is when electrons get to travel through a path or
circuit freely. For this to happen, the circuit needs to be entirely connected, think, like
a circle or loop. If it is disconnected at any point, the electrons cannot flow and the
current will not go. Like when you unplug something from an outlet, or batteries are
not quite in the right place. Speaking of batteries, for our purposes, we will be sticking
to talking about batteries rather than wall electricity, for safety. I guess this matters
less since y’all aren’t in class to actually be doing the labs, but oh well. If you end up
teaching this, stick to batteries because it is safer (though not without risk entirely, as
we will discuss).
3. This and the next 2 slides deal with ways we can classify what is going on an an
electrical system or circuits. They will be on the test, as matching questions. So, first
up, we have VOLTS. This is the potential power a power source could provide. Since
we would be using batteries, A, AA, C, and D batteries provide around 1.5 volts. As
you might expect from the name, 9 volt batteries can supply up to 9 volts of power.
Again, we are going to focus on batteries, so in this case, the volts are the difference
between the positive and negative ends of a battery. So long as there is a difference,
when the batteries are in place, the electrons will be motivated to flow in the circuit
and power whatever you are trying to power (flashlight, remote control, whatever).
The electrons will ALWAYS flow from negative to positive in a battery circuit (hint
hint, might be helpful to know for the test). As the electrons flow, however, the
difference between positive and negative decreases, and once the difference (volts)
reaches 0, there is no longer anything to motivate the electrons to flow, and we would
say the battery is dead.
4. Next up we have AMPS. This is the amount of electricity/electrical current/electrons
that are actually flowing through a wire or circuit at any given moment. If you watch
any renovation shows, like on HGTV, you might remember seeing them use a magic
wand to touch wires. If it lights up and beeps, that means there is current (or amps)
flowing through the wire, and we can measure exactly how much is going through.
Not that you will need to measure it. You just need to know that amps tell us how
much electricity is actively moving through the wire.
5. Lastly we have OHMS, and this is the reason why volts and amps are not the same.
Ohms are the resistance. This can be added in so that not all the voltage of the power
source goes through at once, or it can be the actual thing we are powering. Our most
common thing we would use in the lab would be circuits designed to light a small
light bulb. In that case, the light bulb itself is a resistor, or something that slows down
the flow of electrons. Ohms would be the measure of how much it slows down the
6. In this circuit, which you would have been making in your lab today, (so I made it and
am including a real picture to go along with the diagram, the picture is at the end of
this document), we see the complete circuit. All wires need to be connected, with
metal touching metal. We see the battery on the left (9 volt), and when everything is
connected, the electrons flow from the negative terminal of the battery, through the
bottom wire, then pass through the light bulb (which is held in a bulb holder that just
makes connecting wires easier), then through the top wire, and they end up at the
positive end of the battery. When they are able to do this, the bulb will glow. If
something is not connected correctly, the bulb will not glow.
7. We talked about insulators and conductors already, but then it was in terms of
conducting heat. Now we are talking about electricity. If something allows electricity
to pass through it, it is a conductor. If something does not allow electricity to pass
through it, it is an insulator. One lab you would have been doing today would be
testing different materials to see if they are insulators or conductors. What you would
have seen is basically that metals are conductors, and everything else is an insulator.
8. This and the next slide are scenarios you might encounter on the exam (hint hint). In
this one, the current, or amps (that’s what is actually flowing through the circuit) will
increase if we have more volts (potential power) and less ohms (resistance). Think of
this like yourself. Let’s say you wake up from a great night sleep, with so much energy
and motivation to get stuff done (that’s your voltage, or potential). While you are
getting stuff done, nothing goes wrong or gets in your way (that would be ohms, or
resistance). If you have motivation, and nothing goes wrong, you can get so much
done and your productivity increases (amps, or current).
9. But what if, you barely get any sleep for whatever reason and you find yourself
immediately in a bad mood because you have a headache already, and find yourself
with basically no motivation (low volts). You are still trying to get stuff done, but
things keep going wrong and getting in your way. Like your bunny ate your laptop
charger, your printer is out of ink, your car is broken, etc. These would all be things
getting in your way and slowing your down (ohms, or resistance). If you are starting
with less potential (volts) and stuff goes wrong (ohms), you will end up with
decreased productivity (amps).
10. Please note: You WILL NOT have to use these formulas OR do calculations on the test.
On the test, you WILL end up with a question describing a scenario like this, or the
previous slide. It might be something like “in which circuit will you have more (or less
because I have multiple versions of the question) amps?” then I would have multiple
circuits, with possibly different batteries or resistors. And you would pick the correct
one. If I am asking for more amps, pick the higher voltage battery or the lower ohm
resistor. If I am asking for the lower amps, pick the smaller voltage battery or the
higher ohm resistor. These formulas are the mathematical explanation of what I just
explained. You do not have to use the formulas though.
11. This is the real world example I built based on the diagram on slide 6.
Electric Current

Formed when electrons have a path to flow and
are free to move continuously

Work that will be done by the battery when
moving a charge through a circuit
Force motivating electrons to flow
Electrical Potential (difference) between + and –
sides of power source
Units: Volts (V)

How much charge flows per second through a
wire’s cross section.
Electrical Current Flow
Units: Amps (A)

How much resistance in the wire there is to the
passing current.
Resistance to the flow of electrical current.
Units: Ohms (Ω)
Simple Circuit Example
Insulator vs Conductor

Some materials transmit electricity better than
Materials that transmit electricity well are called
Materials that do not transmit electricity well are
called insulators.
Current increases with…

A larger Voltage
A smaller Resistance
Current decreases with…

A smaller Voltage
A greater Resistance
Ohm’s Law

The amount of electric current through a metal
conductor in a circuit is directly proportional to the
Sample Circuit
Electrical Current & Circuits
 A material that easily allows the flow of electrical
current to pass through it
Metals as Conductors
 ALL metals are good conductors (silver, gold,
aluminum, iron, steel, brass, bronze, mercury,
graphite, etc.)
 Metallic bonds have many free electrons so they can
move freely from atom to atom
Ionic Solutions as Conductors
 Positive and negative ions making up a solution can
produce current by flowing in opposite directions
Human Body as a Conductor
 The human body is primarily made up of solutions,
which makes it a good conductor

If you touch a charged object, some of the charge will be
transferred to you
 Material that does not allow electrical current to flow
through it easily.
 Examples: Wood, glass, porcelain, plastics, paper,
air, and pure water.
 If water is an insulator, why can’t we take baths with
toasters and hair dryers?
 We do not bathe in PURE water
 Even if we did, the salt from our bodies would turn

the water into a solution

(Think hypotonic!)
Recap from last time…
 Volts measure how much potential there is for
electrical current
 Amps measure how much electrical current is
actually flowing
 Ohms measure how much resistance there is to the
flow of electrical current
Simple Circuit with Switch
Series Circuit
 Bulbs follow each other along the same path.
 Bulbs are sharing the voltage of the battery.
Parallel Circuit
 Bulbs have independent paths to the battery
 Each bulb is independently connected to the battery
Which type of circuit…
 Do we find in our homes?
Which type of circuit…
 Do we find in strings of multi-colored lights?
A Few Words About Safety
 When working with electricity in the lab, safety
should be your number one priority.
 Use the lowest voltage power source possible.
1.5 V and 3 V batteries are relatively safe
 9 V batteries require more supervision
 Avoid electrical power from wall outlets, especially with students
 Standard wall voltage in North America is 120V.

New Electrical Circuits
Electromagnetism Unit—Day 3
1. There is a bit of a recap in the first part of this PowerPoint, then we will get to 3 new
circuits and I will include pictures of them how y’all would build them in lab.
2. Conductors of electricity are things that easily transmit electrical current (or
electricity, or electrons) to pass through it.
3. As we said last time, ALL metals make good conductors. You do not need to know the
second bullet point since we didn’t cover metallic bonds in the chemistry unit either. So
for this, all you need to know is that metals conduct electricity.
4. Ionic solutions are things where you have an ionic compound dissolved in something
else. These also act as conductors. These can be things like salt water, or pool water
(which has ionic compounds dissolved in it to disinfect the water). This is why you will
be asked to get out of pools, and should not be in the water at the beach when there is
lightning happening, because if the lightning strikes anywhere on the water, the water
would act as a conductor and you would essentially be struck by lightning.
5. Unfortunately for us, since we are mostly made up of ionic solutions, we are
conductors of electricity, which means that we can be electrocuted/struck by lightning.
6. Insulators are things that do not transmit electricity. Wood, glass/ceramics, plastic,
paper, air, and pure water are all insulators. If you were building your circuits, you
would see how air acts as an insulator, because if the wires are not actually touching
metal, the light bulb will not light up. There is a lab we won’t be doing, where you
tested salt water and sugar water to see if they were insulators or conductors. The salt
water (which is ionic) would be a conductor. The sugar water (not ionic), would act as
an insulator.
7. So wait a minute. At least one of you is probably wondering why there are warning
labels on blow dryers to not use them, and why do we see people getting electrocuted
and killed in movies because someone throws a toaster in the bath tub? If water is an
insulator, none of these things things should be able to electrocute you. What’s up with
8. You don’t need to know this for the exam, I just think it’s neat. But we do not bathe in
pure water. The water that comes out of the faucet is actually ionic because of the
disinfectants we use to keep it clean. Even if you decided to bathe in deionized water (it
would be expensive so, uhm, don’t), once you sit in the bathtub, salt from your body
goes “oh no! this pour water! It has no salt! Let me help” and starts putting salts into
the water for you, which means it will be ionic soon enough. You are safe using your
phone in a bath, and if it falls in, you will be more mad that your phone is wet than
anything. But DO NOT EVER use your phone while it is plugged into a wall outlet or
power bank while you are in the tub/pool/water. If it falls in, you could be
9. Last recap slide! Volts tell us how much potential power a power source could
theoretically supply in a perfect world. Amps tell is how much electricity is actually
flowing through a wire/circuit at any given moment. Ohms are the reason the two
other numbers might not be the same, since it is the resistance or what slows down or
stops the electrons.
10. New circuit #1! A circuit with an off/on switch! This one requires all the same tools as
the simple circuit from last time, but we add in an extra wire and a switch. In figure 1 at
the end, I show it both on and in figure 2, I will show it off so you can compare.
11. In a series circuit, you have multiple light bulbs that all share the same path to the
battery. This means they also share the same voltage from the battery. These bulbs will
not be as bright because they are sharing the battery. In a series circuit, if one light
bulb breaks, dies, or becomes disconnected, all of the light bulbs will go out because
that missing battery means the circuit or path around in a loop is no longer connected.
In figure 3 at the end, I will built this with 2 light bulbs, and in figure 4, I will show it
with one bulb disconnected so you see what happens to the other. Basically it is the
same as the switch one, but with an extra bulb holder/light bulb in place of the switch.
12. Last new circuit! In a parallel circuit, each of the bulbs will have its own, independent
connection to the power supply (battery, in our case). This means the bulbs should be
as bright as they were in the switch circuit. This also means that if one goes out, the
other bulbs will remain lit. If you are using a battery, the battery will die faster in this
case since both lights are using the total voltage. In figure 5 I will build it with 2 bulbs,
and in figure 6 you will see the same circuit with one bulb removed. Please note that
the other bulb stays lit.
13. Between series and parallel, which type of circuit do we find in our house? Parallel!
Luckily. Can you imagine if one light bulb went out, and as a result, every single light
bulb in the whole circuit went out? That would be terrible. As it is now, we can have
one light go out and wait months to replace it if we want. Please note, by this, I mean
individual lights, because (and don’t focus on this last bit for the exam) “circuit
breakers” which are found everywhere are different and actually break the house up
into chunks of series.
14. Also not for the test: If you’ve ever used these, you probably have noticed that when
one light goes out, the whole string becomes useless, which would make them series.
But as bulbs switch to LED lights, which use less power, we are able to build them in
only chunks of series. What this means is you will have, say, a string of 100 lights,
broken up into 10 groups. Each group will have 10 bulbs. These 10 bulbs will be in
series, but the whole chunk will be in parallel with the 9 other chunks. This means if
one bulb goes out, you will only lose that cluster of 10 bulbs instead of the whole string.
Yay, science!
15. Since we aren’t doing the lab, this is less important, but if you do this in your future
classroom, always use the lowest voltage power supply for what you are trying to do.
In our lab, the strongest voltage we would use is 9volt batteries. Please do not
experiment or play with wall electricity! The basic outlet in the US is 120 volts, which is
definitely enough to cause you damage at the very least.
Figure 1. Switch Circuit: ON (slide 10)
Figure 2: Switch Circuit: OFF (slide 10)
Figure 3: Series Circuit: 2 bulbs in place (slide 11)
Figure 4: Series Circuit: 1 bulb missing (slide 11)
Figure 5: Parallel Circuit: 2 bulbs in place (slide 12)
Figure 6: Parallel Circuit: 1 bulb missing (slide 12)

Force of attraction or repulsion based on
electron arrangement
Magnets always have two poles (ends)
 If a magnet is cut it will still have two poles
 Like magnetic poles repel
 Unlike magnetic poles attract

Other magnets
 Materials with

› iron,
› nickel, and/or
› cobalt

A magnetic field is the area in which
magnetic forces act
› Magnetic force will extend to this boundary

Earth has a magnetic field
› Extends almost 600,000 km above Earth
› Creates Aurora/Australis Borealis

Caused by fluids

Naturally occurring
› Lodestone

Permanent magnets
› Difficult to magnetize and take a long time
to lose magnetism

Temporary magnets
› Easy to magnetize and lose magnetism
when not in contact with a magnetic field

Compasses point to Magnetic North
everywhere in the world, but they are
not perfect.
› Do not like magnets
› Do not like large metal objects
Electromagnetism—Day 4
1. Magnets. I’m sad we can’t do this one in person, because I basically leave us a bunch of time
to just have fun, playing with magnets. Ah well.
2. So I’m pretty sure everyone knows what a magnet is, and everyone has at some point used
a magnet to stick something to likely a fridge. The thing with magnets though is that while
we all know what they are, most people don’t understand what makes them what they are.
In the most basic terms, magnets are things that attract and repel based on electron
3. Domains are parts of magnets, or clusters of atoms in a metal. If the domains are pointing
in random directions, the metal will not be magnetized. If the domains are oriented so they
are pointing in the same direction, the metal will be magnetized. The more domains are
pointing in the same direction, the stronger the magnet will be. Metals containing iron,
nickel, and/or cobalt can be magnetized.
4. Magnets have two sides: North and South. Do not call these positive and negative! On the
previous slide, when we look at the illustration of the magnetized material, the
arrows/domains are pointing towards the North pole of the magnet, and the other side is
the South pole of the magnet. If a magnet breaks in half, we end up with two completely
functional, just smaller magnets. Like magnetic poles will repel, meaning North and North
will push away from each other (if you have 2 magnets at home, try to get them to touch
each other). Opposite magnetic poles will attract, which is why magnets can stick to things.
5. So what is attracted to magnets? Basically the same things that can be turned into magnets
(any metal containing iron, nickel, or cobalt). Of course other magnets are attracted to
magnets, so long as the North and South poles are pointing towards each other, that is.
6. A magnetic field is just how far out the force of a magnet extends. The more powerful the
magnet, the further the field extends. If you have a magnet on your fridge at home, when
you go to stick it to the fridge, once you get close enough, you will feel that slight pull as it
sticks. Once you cross that and get close enough for it to stick, that’s in the magnetic field.
We can see a visual representation of how far the magnetic field extends by placing
magnets around iron filings.
7. Here you can see a magnet surrounded by iron filings. The iron filings will look organized
and structured as far out as the magnetic field extends.
8. More magnetic fields. This is the same tech that is used in Etch A Sketches. At some point,
you’ve maybe also played with iron filings and a magnet, and it is really fun and neat to see,
but in your hypothetical future classrooms, I would encourage you to be careful having
loose filings for students to play with. If someone sneezes, you could easily have students
ending up with iron filings in their eyes, which is, obviously not good. To get around this,
what I do is put the iron filings in a clear zip top bag. That doesn’t stop the magnetic field,
so you can still see the patterns, and then it’s also neat to see the bag stick to the magnets.
9. Depending on how young your students are, or if you need to adapt lessons for students
with special needs, another alternative is to have the magnet on the loose filings on a piece
of paper, then carefully move the magnet out of the way (which should leave most of the
filings still organized) and then put a piece of clear contact paper over them to hold them in
place forever. This way students could see the magnetic field safely, and also have an
activity where they match the magnet to the magnetic field, since there would be a gap
matching the size and shape of the magnet.
10. Lucky for us, the Earth acts as a magnet and has a magnetic field. This is lucky for us,
because the magnetic field is one thing that helps to protect us from radiation from the sun.
Our magnetic field is pretty big, and extends 600,000 km (or 372,822 miles) above the
surface of the Earth. Some other planets also have magnetic fields, just not all of them. Our
magnetic field is caused because of the molten (which means liquid) iron rock inside the
Earth. As this molten rock moves around through Convection Currents (remember those
from Chemistry? It’s okay if not. You don’t need to explain it here), the motion of the rock
generates our magnetic field. So even though our Moon is made of the same rocks as Earth,
it does not have a magnetic field because it is completely solid and has no liquid rock
moving around (hint hint, why the Moon doesn’t have a magnetic field would be helpful to
know for the test).
11. You do not need to know this for the test, but my favorite part about our magnetic field is
that it helps to produce Aurora Borealis (northern hemisphere) and Australis Borealis
(southern hemisphere). You might be more familiar with these by their not-technical
names: Northern Lights and Southern Lights. These happen when charged particles from
the sun hit molecules in our magnetic field. Then the molecules in the magnetic field get
excited and glow. The color of the glow is determined by what element it hits. Nitrogen will
glow pink and purple, while oxygen will glow green and red. To see these in person, your
best bet is to get as far north or south as you can. The closer you are to one of Earth’s poles,
the better your chances are. It also needs to be dark (so don’t go in summer when there’s
less daylight), clear weather, and the more active the sun is, the better your chances are to
see it.
12. You do not need to know these for the test, so you can skip this if you want. But there are
three types of magnets. Naturally occurring ones are literally things where you dig up a
rock and it is magnetic. Permanent magnets I think are tricky because of the name. When
we think of the word permanent, we tend to think of forever. But permanent magnets are
metals that started out not magnetic, and then became magnetized. They are able to
maintain this magnetizing for a while, sometimes quite a lot, but it does fade and they will
eventually become demagnetized. Everyone seems to have that one family member with a
fridge covered in magnets, and you’ve probably seen what happens as some get older and
start to be more likely to fall off. Those are still permanent magnets because they are able
to maintain their magnetism, just not forever. You’ve also maybe at some point had a hotel
room key that stopped working. Those stripes on them are magnetic and these are also
permanent magnets, but just weak ones that are only designed to last a few days, and are
weak enough holding them next to your cell phone can undo it. Temporary magnets are
only magnetic when there is either another magnet touching them, or while there is
electrical current going through that generates the magnetic field. These can be turned on
and off. So if you’ve ever seen a magnet lift a car, that is a temporary magnet because you
need to be able to turn it off, or else the car would be stuck there forever.
13. Since the Earth has a magnetic field, we can use that to our advantage for navigation, by
using compasses. Important to note (hint hint): Compasses will point to the Earth’s
Magnetic North Pole from everywhere on Earth, yes, even in the Southern Hemisphere
(what you don’t need to know is that we just have to add a little weight to compasses to be
used in the south). Compasses are great, but they are not perfect. They do not function well
and get confused when they are around magnets, and large metal objects. If we were in lab,
we would be doing an activity where we had compasses and would basically use magnets
to confuse them and watch the needle spin and move.
Waves, Light, and Sound
Electromagnetism—Day 5
1. Unfortunately there are kind of a lot of smaller demos we will be skipping today, but no
huge labs at least, so yay.
2. Waves are traveling energy, and do not actually take any material with them, so the
material goes back to normal after the energy passes through.
3. You do not need to define them for the test. What you need to know is on the next slide so
let’s go there
4. You will need to identify the two types of waves in pictures for the exam. The best
examples of transverse waves would be ripples in water. Let’s say we throw a rock into
water, the ripples in the surface of the water go up and down as they spread out. The best
example of a longitudinal wave is traffic. This one deals with compression and expansion,
so imagine the compression as a red light, where all the cars stop and end up close
together. Think of expansion as how cars will tend to spread out in the road after not
having to stop for a while.
5. You will also need to identify the parts of a transverse wave for the test. Amplitude is the
height of the wave, so from the mid point to the top or bottom. Crests are the tops (like
the crest of a mountain). Troughs are the bottoms (like water troughs where you give
water to farm animals). Wavelength is the distance between two crests. Skip cycle.
6. Pretty sure you all know what sound is. But what you might not know is that it is a
longitudinal wave that comes from vibrations. You’ve maybe been to a loud concert where
you can actually feel the vibrations of the music. Sound has to travel through a material,
like air. So there is no sound in space, and if we were having class on the moon you would
not be able to hear me because there is no atmosphere to carry the vibrations.
7. You don’t need to know this for the test, and I am also pretty clear you know the
difference between high (opera singer) and low (bass) sounds, and definitely volume.
8. Sound travels at different speeds based on the state/density of the material it is traveling
through. The higher the density the faster the sound will travel. This means it travels
faster in liquids than in gas, and faster in solids than both. This is why if you are in a pool
and under the water, you can hear sounds, but they are moving so fast you can’t interpret
from which direction it’s coming from like you could in air. Sound is the fastest in solids,
which is why you see people spying by physically putting their ear on the door.
9. Light is a transverse wave which means it can travel through empty space, which is great
for us because light from the sun gets to Earth so we get to live, but personally it is great
for me because light from other planets, stars, galaxies, and nebulas, so reaches us, which
means I get to have a job teaching Astronomy labs.
10. Light/transverse waves have different wavelengths and frequencies, and as humans, we
only see a small subsection of this. Birds can see into the UV range, and snakes can sense
into the infrared section. (you don’t need to know the bird/snake thing)
11. Wavelength (size) and frequency (power) are inversely related, which means that if one
goes up, the other goes down. So if something has a large wavelength (meaning it’s big), it
will have a small frequency (low power). If something has a small wavelength, and a high
frequency, it is dangerous because smaller wavelengths can get inside us, and they have a
higher frequency which means they are able to do damage when they are there. We know
that UV is dangerous since it’s what comes from the sun and causes sunburns (and
eventually can contribute to skin cancer). We also understand that X-rays are dangerous
enough, since they limit how many you can get, and put those lead jackets on when you
get them done at the dentist. Gamma rays, or γ rays, or simply radiation, is the most
dangerous. The good thing is that we can use this as a cancer treatment, a less serious but
relevant example is that gamma radiation is what caused Brice Banner to turn into the
Incredible Hulk, but radiation is also what caused deaths, birth defects, and lasting genetic
issues in people who were exposed to radioactive material and more specifically, atomic
12. This chart just shows the whole light spectrum. Notice that as frequency/energy
increases, wavelength decreases, and vice versa. The tiny little segment in the middle is
“Visible Light” or what humans see. Also yes, radio waves are actually a type of LIGHT
even though we generally associate them with sound.
13. Same thing as the previous slide but in reverse order, and with objects for scale. Keep in
mind that Gamma, X-Rays, and UV are the dangerous types of light, while Infrared,
microwaves, and radio are the safe ones.
14. So now let’s focus on just visible light, or what we see. The visible light spectrum has 7
main colors: Red, Orange, Yellow, Green, Blue, Indigo, Violet. You can remember these by
thinking of our good friend, Mr. ROY G BIV. Red is the closest to infrared, so it has large
wavelength and small frequency, while violet is closest to UltraViolet, which means it has
smaller wavelength, and larger frequency
15. The top picture shows a full rainbow, or the full spectrum of light we see. This is (not
coincidentally) the exact same amount of visible light the sun produces since we evolved
to see under the sun. The bottom one shows what a standard fluorescent lightbulb would
produce. As you can see, it does not make all the colors and there are many gaps. This is
why pictures you take inside don’t look the same as pictures taken in natural/sunlight. If
you are doing anything artistic that requires color blending/matching, natural light is
your best friend.
16. So back to our friend Roy G Biv, why do we see color? Let’s say I am wearing a red shirt.
We see my shirt as red because it reflects red and absorbs all the other colors of light. We
traditionally would wear lighter colors in summer because the closer something is to
white light, the more light it is reflecting. The less light something absorbs, the cooler it is,
meaning light colors help keep your temperature lower in the summer. We traditionally
would wear darker colors in the winter, because darker colors are absorbing more light
(which means absorbing more heat). If something is black, it is absorbing all the colors of
light and reflecting none. So if that’s why people don’t wear black in the summer (unless
you are a metal head/perma-goth like myself…)
17. If we look at light, it travels at one speed, no matter what it is traveling through. This is
300,000,000 m/s (or about 670,616,629 miles/hour), and that is SIGNIFICANTLY faster
than sound can possibly travel. This means that we see things before they hear them.
Lightning and thunder are the same thing, but the reason we see lightning then wait to
see how long it takes until we hear the thunder is because of the difference between the
speed of light (lightning) and the speed of sound (thunder).
18. The last thing of the unit! Yaay. These are two types of optics we see, but really will not be
able to effectively cover. So all I will ask of you on this is to identify examples. Refraction
uses lenses and the examples you might see of this would be microscopes, glasses, contact
lenses, rainbows (which is water in the atmosphere refracting sunlight to project the
spectrum), or if you’ve ever sat with your feet dangling into a pool, it looks like your legs
are bent oddly. Reflection is anything that, well, reflects. It uses things that are reflective,
like mirrors. Other examples of this would be the visibility of the moon (since it produces
no light of its own and only reflects sunlight), or reflections in water or mirrors.
Waves, Sound, and Light
 Travelling disturbance carrying energy from place to
 No transfer of mass or material.
 Medium goes back to normal after wave passes.
Types of Waves
 Disturbance is
 Disturbance is parallel
perpendicular to the
direction the wave
to the direction the
wave travels.
Transverse vs. Longitudinal Waves
Parts of a Transverse Wave
 Longitudinal wave generated by a vibration
 Requires material for transmission
 Will not travel through a vacuum
 Space?
Characteristics of sound
 Pitch-frequency of the sound (high or low)
 Thick vs thin string
 Tension on string
 Loudness-sound pressure or amplitude of the sound
 We will now test the difference between different
tuning forks in an out of water.
 Speed of sound
 In solid: 5,200 m/s
 In liquid: 1,400 m/s
 In gas: 340 m/s
 Changes based on temperature
 We will now test the speed of sound through different
densities of material.
 Transverse waves generated by the vibrations of an
electromagnetic field
 Does not require a material for transmission
 Can travel through a vacuum
Wavelengths in Light
 Electromagnetic waves are of many different
frequencies and corresponding wavelengths
 Only light waves in a small frequency range are visible
to the human eye
Wavelength, ctd.
 As the frequency increases, the wavelengths get
 Short wavelength lights (UV, x-rays, γ rays) are high
energy and therefore hazardous
Visible Light
 Color corresponds to the frequency of a light wave.
 Visible light spectrum includes: red, orange, yellow,
green, blue, indigo, and violet or Roy G Biv
 Red has the longest wavelength and shortest frequency
 Violet has the shortest wavelength and highest
 Does the sun emit all colors of the visible light
 We can check with spectroscopes!
Why do we see Color?
 Visible spectrum: ROYGBIV
 A shirt is red because it absorbs every color of light
but red.
 Why do we wear white in summer and black in winter?
 What if Sun’s light was purple?
Speed of Light
 Average speed of light is 300,000,000 m/s
 Remember that sounds ranged from 5,200-340 m/s
 Light is much faster!!!
 What does that mean for us?
Refraction vs. Reflection
 Uses Lenses
 Uses Mirrors
 Examples: Microscopes,
glasses, contacts,
 Examples: Visibility of
the moon, reflection in
water, reflection in

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