"How does my (charged) balloon stick to the wall?"
The negative charge on your balloon is making the wall's surface positively
charged, and then these unlike charges attract.
How did the wall become positively charged? The wall has atoms and all atoms
have negative charges (electrons) and positive charges (protons). The positive
protons are deep inside the atom in the nucleus; the negative electrons surround
this nucleus. When a negatively charged balloon comes up to the wall, the
negative electrons in the wall's surface atoms are repelled (like charges
repel). The electrons are pushed to a degree to the "back side" of the
atom. That will leave the "front side" (the surface of the wall) mainly
positively charge (due to the protons). Now the charges that are closest to each
other (wall's protons and balloon's
electrons) will attract each other. Walla - the balloon will now
"stick" to the wall.
"How does my (charged) balloon bend the water stream?"
Water molecules naturally have a
negative side (the oxygen) and a positive side (the hydrogens) This is because
of how the oxygen and hydrogens share electrons. Water molecules are called
"dipole molecules." The
negative charge on your balloon is attracting the molecule's positive side, and repelling
the water molecule's negative side. This causes the water molecule to turn about
so that its positive side (the hydrogens) faces the negative balloon. Now the
balloon will attract the stream of water.
This animation that illustrates this force: http://www.colorado.edu/physics/2000/applets/h2ob.html
(uses an electron and a water molecule)
"What is the tingling irritation that I feel when I touch my tongue
to the terminals of a 9V battery"?
You are feeling electric charge move across your tongue.
The terminals of the battery are the connections to the electrical potential
energy stored within the 9V battery. When you touch both terminals with
your wet tongue, you are providing a complete path for the charges to move
from one terminal to the other. Your wet tongue is a great conductor of
electricity. When you touch your tongue to both of these terminals, you
have set up a path for the electric charges to easily flow through.
"Does the wall switch give the light its electricity"?
No, the wall switch does not give the light its electricity, it only
controls the flow of electricity/ electric charge. This flow of electric
charge needs a continuous path/ circuit. When you turn the lights off,
the wall switch breaks this path (or "opens" the path). We say that the
switch is "open." When you turn the lights on, you are "closing" the path,
you are connecting the path for the charge to flow through. The switch
is "closed".
The source of the electricity (what provides the electrical energy) is
the electric power plant's generators. The power plant gives us electricity,
it provides the voltage needed to push the charge around the paths/ circuits.
This charge flows through the filament of the light bulb, the filament
uses this moving energy to produce light energy.
"Why do all the Christmas light go out when I remove one of the bulbs"?
The bulbs are essentially wired is series, remove one bulb from the
circuit (this will 'open' the circuit) and all the other bulbs go out. Why don't all the bulbs go out when that one
bulb burns out (i.e. its filament
breaks "open")? Within each bulb is a tiny parallel circuit. If the filament breaks, there is an alternate path for the current to flow
through.
"What is a short circuit?"
An electric circuit is a path where electron's can flow out from the
voltage source, all the way around through an electric appliance (or light?)
and back again. A short circuit occurs when the wires in the circuit totally
bypass the appliance. The electron's will then have a path that they can
flow through without going through the appliance. Not only will there be
no electron flow/ current flow to the appliance, there will also be no
resistance to the current that is flowing. The current flow will be very
great and the wires could melt down and a fire could start.
"How do magnets lift objects?"
A magnet can lift an object by making that object a magnet!
Magnets can only lift certain objects. (What kind of objects can be
lifted by a magnet?) These objects are made of the same kind of material
that magnets are made out of. Let's consider a paper clip. The paper clip
has within it regions that are magnetized. The paper clip as a whole is
not a magnet, because these small magnetized regions are not all lined
up together, with their north poles all pointing in one direction and their
south poles all pointing in the other. When a magnet comes near the paper
clip, the pole of the magnet closest to the paper clip will attract the
opposite pole of the magnetized regions within the paper clip. These regions
within the paper clip will line up together and the paper clip will become
a magnet temporarily. The two magnets (the permanent one and the
temporary paper clip one) will be attracted to each other and stick together
and you can then lift up the paper clip with the magnet.
A paper clip "sticks" to the north pole of my magnet. If I turn the
magnet around will the paper clip still be attracted to the magnet? Or
will the south pole of my magnet repel the paper clip?
(Teacher Note: It is best to just give the student a magnet and pile
of paper clips and let him/ her try it out!)
"How does this magnet pick up this long
chain of paper clips?”
A magnet can lift a paper clip by making that paper clip into a
(temporary) magnet! And in turn, that newly created “paper clip magnet” can
lift up another paper clip! Magnets attract materials that are ferromagnetic
(for example, iron). Let's consider a paper clip. The paper clip has within it
tiny microscopic areas that are already magnetized. These areas are like tiny
magnets (called magnetic domains) each with their own north and south poles. The
paper clip as a whole is not a magnet, because these tiny south-north pole areas
are all jumbled up. When the south pole of the magnet comes near the paper clip,
it will attract all of the north poles of the small magnetic domains within the
paper clip (and vice versa). These domains within the paper clip will now be
lined up together and the paper clip will become a magnet (but only
temporarily). The two magnets (the permanent one and the temporary paper clip
magnet) will be attracted to each other and “stick” together and you can
then lift up the paper clip with the magnet. The magnetism of the paper clip in
turn aligns the magnetic areas within the next paper clip, attracting opposite
poles one to another. The two “stick” to one another, and paper clip by
paper clip, this process causes a chain of paper clips to hang down from the
original magnet.
"When I break this magnet in half, will
its magnetism be gone?”
When I break this magnet, will its magnetism be gone?
No! The magnet is magnetized throughout its whole body. Break the magnet in half
and you will have two smaller magnets. If you were able to look deep within the
magnet, all the way down to the microscopic atomic level, you would find groups
of atoms that are magnetized. These groups (called magnetic domains) are like
tiny magnets each with their own north pole and south pole. In a material that
can be magnetized, ex: paper clip the magnetic domains are all jumbled up. But
the domains within a magnet are lined up together, with all the north poles in
one direction (attracted to the south poles) and the south poles in the other
direction (attracted to the north poles). These domains start at one end and go
all the way through the magnet to the other end. [Picture/ diagram?] You can
break the magnet in half and each half will still have its tiny magnetic
domains, all lined up and pointing in the same direction. You will now have two
magnets.
[Teacher Note: In the process of breaking the magnet, the domains directly by
the broken edges can be distorted a bit due to the stress while breaking the
magnet.]
"How does water power turn
into electricity?" (or "What is hydroelectric power?")
[First qualify with child as to what water power is.]
An electric power plant uses water power to generate
electricity. These power plants use the moving energy of steam (from boiling
water) or the moving energy of falling water (from dams or waterfalls).
The moving water pushes against the blades of an electric generator's turbines.
The turbines turn the wires within the generator electromagnet. Because of the
relative motion of the wires and the electromagnet, the electromagnet exerts a
force on the electrons in the wires. This force makes the electrons move through
the wire. Now you have electricity flowing.
[There are different ways to get the water boiling. One
method is to burn coal or oil, another is to use the energy of a nuclear
reaction to heat and boil the water.]
"What is an electromagnet?"
An electromagnet is a device that "makes" magnetism from
electricity flowing through a wire. To make an simple electromagnet strong
enough to pick up heavy (magnetic) materials, you need to design the electromagnet
in the following manner. Wrap an insulated wire many
times around an iron core (for example: a large nail or a screwdriver). Attach
the ends of the wire to a battery. The greater the voltage source, the greater
the current. The thicker the wire, the greater the current. The greater the
number of coils, the greater the magnetic field. Watch out though: if the
current is too great, the electromagnet can get very hot!
"Why does the sun
shine in the daytime and the moon at night?"
Daytime is the time when it is light/ bright outside,
and the sun has to be in the sky in order for there to be a lot of light
about. Our part of the Earth is facing the sun, when we have daytime. the
other part of the Earth is facing away from the sun, they can not see the
sun, and they have nighttime. They are actually in the shadow of the Earth!
As the earth turns about, we move into the shadow of the Earth and the
sun looks like it is setting. It is now nighttime for us. Nighttime is
dark, because there is no sun in our part of the sky.
When we see the moon shining, it is not making its own
light like the sun does, but it is reflecting sunlight to the Earth. It
is easy to see the moon "shining" at night, because the sky is so dark,
which makes the moon appear to be very bright. The moon can also be seen
during the daytime, but you have to look carefully over the sky to find
it. Because the sky is so bright with sunlight, it is harder to find the
moon during the daytime than it is during the nighttime.
[Teacher Note: the subject of the phases of the Moon
could easily come up at this point!]
"What makes a shadow get
longer or shorter?"
You have probably noticed your shadow shrink and grow
when you pass by a tall lamp post at night. Depending on where you are
and where the light source is, your shadow changes size as you move about.
Your shadow is big when your body blocks a large amount of the light. And
your shadow will be small when your body blocks only a small amount of
the light. For a light high above you, the closer you are to the light,
the smaller your shadow will be, because your body is not blocking
much of the light. For a lamp on the table, the closer you are to the light,
the more of the light will be blocked by your body and the larger your
shadow will be.
"To see my feet in the mirror,
do I need a larger mirror, or can I just step back from my mirror?"
If you can not see your feet in the mirror when you are
close up to the mirror, you will not be able to see them when you step
away from the mirror. A larger mirror will not help you! If you can see
your feet when you step away from the mirror, try stepping forward a bit
and with each step, look carefully into the mirror, as far down as you
can and you will be able to still see your feet. In order to see you full
image, you need a mirror about half of your height.
[Note: I am assuming a vertical mirror and a flat horizontal floor.
Also, if there is a cabinet or dresser in front of the mirror,
this might block your view of your feet. It will be in your "line-of-sight",
so to speak.]
"Is fluorescent light better
than regular light?"
Fluorescent light uses less electricity than regular,
incandescent light bulbs. Therefore it is cheaper. However, fluorescent
light does not produce all possible light waves that make up white light.
It looks like white light, but not all of the colors that make up white
light (visible light) are in it. As a result, some shades of red, or green, or blue, etc.,
will look different under fluorescent light than under an incandescent
light.
"Why is the sky blue?"
The sun produces white light, which is actually a combination
of all of the colors. It is the blue and violet wavelengths of sunlight that
are scattered the most by the molecules in our atmosphere. Thus when we look up
in any direction in a clear sky, we see light coming to us from the molecules scattering about
this blue light.
What happens to the rest of the sunlight? It passes straight on through the
atmosphere, though some of it may be scattered out by dust or other larger
molecules. Water droplets in clouds scatter about all of the different colors/
wavelengths, thus clouds tend to look white.
What does the moon's sky look like? On the moon there is no atmosphere, therefore no air
molecules at all to scatter light about. No light is coming from the different
parts of the "sky", except for the part of the sky with the Sun and the distant
stars. As a result, the astronauts standing on the moon saw a black sky
surrounding the sun and stars.
"What is a rainbow made
of?"
A rainbow is made from sunlight passing in and back out
of water droplets in the sky. These water droplets act like tiny little
round prisms, separating the white sunlight into all of its colors. The
sunlight is bent/ refracted as it enters into the water droplet, bounces/
reflects of the back of the water droplet and passes back out of the front
of the droplet. Each color from each droplet will now has its own path.
We see red light coming from the droplets at the top of the rainbow and
violet light coming from the droplets at the bottom of the rainbow. And
in between those droplets, all of the other colors are also being separated
out (from the white light) by other droplets.
Have you ever heard of a moonbow? That's a rainbow made from moonlight - The best time to see one is when the moon is full, don't forget to "turn your back to the moon"! http://wug.physics.uiuc.edu/courses/phys150/spring02/slides/chap23/sld009.htm (In this image the sky looks blue and the grass green, like they do during the daytime. It may be hard to believe that this picture was taken at night. The photographer had to expose the film for a "long" period of time (30 sec.) in order to "catch enough" the moonbow light. At the same time he or she caught a lot of scattered moon light from the sky and grass, etc.
Is radiation bad for you?
It depends on the kind and the amount of radiation that your
body is exposed to.
Radiation is made up of electromagnetic waves. There are lots of different
kinds of radiation: visible light, ultraviolet light, heat radiation/ infrared
light, microwaves, radio waves, X-rays, gamma rays. (Each of these electromagnetic
waves have different frequencies.)
Visible light is great to see things by, but too much light
can hurt our eyes. (Never look directly at the Sun!)
Heat radiation (IR - infrared radiation) from a bonfire feels great on a cold day,
but too much can burn your skin.
Ultraviolet (UV) light helps our bodies' cells form Vitamin
D, but too much will burn/ tan our skin and cause premature aging of our
skin and for some people skin cancer. (UV photon frequencies can trigger
chemical reactions.) We can enjoy and our bodies can tolerate visible light
from the sun all day long, but not the ultraviolet light from the sun.
X-rays help a doctor find a broken bone or a tooth cavity
- but too much can damage cells in our body. Dentists do not like
to take more than two annual X-rays of your teeth (and each time
they do, they stand behind a heavy wall to protect themselves from those
X-rays).
Gamma radiation can be used to kill cancer cells, but they
can also kill healthy cells.
"What is the difference
between 'good' ozone (which protects the Earth from UV radiation) and 'bad'
ozone (in smog)?"
'Good' ozone and 'bad' ozone are chemically the same thing (both
are the same molecule, O3, made up of 3 oxygen atoms). Ozone
is highly (chemically) reactive and what makes one 'good' and the other
'bad' is their location.
We live (and breath!) in the bottommost part of our atmosphere (the troposphere).
Ozone in this part of the atmosphere (due to pollution) could chemically
react with our respiratory/ lung cells, causing respiratory problems.
Above the troposphere is the stratosphere, within which there is the "Ozone
layer" (~20 kilometers above our heads). This layer of our atmosphere blocks
ultraviolet (UV) light. The chemical reaction cycle O3 (ozone)
<=> O2 (oxygen) absorbs some of the sun's UV radiation (and emits IR
radiation).
"What makes this "glow-in-the-dark"
lizard/ frog glow after I turn out the lights?"
When then light was on, the atoms and or molecules within
the frog were "storing up" the light energy. These are special atoms/ molecules
that have the ability to absorb light energy, and release this energy later
(in the form of light). It doesn't release the light all at once, but bit
by bit, until all of the "stored energy" is gone. This process is called
phosphorescence.
"What makes neon colors
so bright?"
These neon or fluorescent colors look bright because
they are absorbing high energy packets of light (ultraviolet light) and
releasing that light in the form lower energy packets (visible light).
The ultraviolet light is not visible to our eyes, but this "newly produced"
light is. So it looks like that bright green sign is producing its own
light. Instead, it is the fluorescent atoms in the sign that are changing
invisible light into visible light.
"Does 'Nuke it in the microwave'
mean that there is a nuclear reaction going on in the microwave?"
No, there is no nuclear reaction taking place inside
of your microwave! Microwave ovens produce microwave radiation. This electromagnetic
radiation is absorbed by molecules of water (& fat!). When these molecules
absorb this energy, they start to move more. They have more heat energy.
This absorption process changed the electromagnetic energy into heat energy.
These changes took place between atoms and molecules. No change occurs
in the nucleus. No nuclear reactions will take place!
"What makes seasons and
why do we have four of them?"
When our part of the Earth is directly facing the Sun
for most of the day, we have summer. You probably have noted how the Sun
is up high in the sky on summer days. In the winter time, the Sun is low
in the sky. Our part of the Earth, during wintertime, is not facing the
Sun directly, and less of the Sun's energy is able to reach us. Thus in
the winter it is colder. What is happening in order for this change to
take place? The Earth moves/ revolves around the Sun. The Earth's axis
is not straight up and down with respect to how it moves around the Sun.
Our part of the Earth is titled back, away from the Sun in the wintertime.
By the time the Earth has revolved half-way around the Sun, our part of
the Earth will be tilted toward the Sun and it will be summertime. In between
winter and summer, our part of the Earth will be warming up as the Sun's
ray are more and more directly shining on us (springtime). In the fall,
as the Earth continues on its journey around the Sun, the Sun's rays will
be gradually shining less and less directly on us, our part of the Earth
will be cooling off more and more.
"What makes the moon change
shape?"
The moon is not really changing its shape. It is just
changing the amount sunlight that it is reflecting on to us.
One side of the moon is always facing the Sun. (Just
like on Earth, there is always daytime somewhere. Except for, of course,
during an eclipse!) If the part of the moon that has full sunlight is also
completely facing us, then we will see a full moon. If that part of the
moon is not facing us at all, then we will not have any sunlight reflected
to us from the moon. The moon will appear "black". We call that a new moon,
even though we see nothing at all!
How much of the sun lit part of the moon is facing us
depends on where the moon is in its orbit about us. If the moon is between
the Sun and the Earth (but not directly, or else there would be a solar
eclipse!), then we would have a new moon. During approximately a half month's
time, the moon will revolve halfway around the Earth, and the sunlit portion
of the moon will "grow" more and more. This is referred to as the "waxing"
of the moon. When the moon is on the back side of the Earth (but not directly,
or else we would see a lunar eclipse!), we would see the full sunlit side
of the moon, a full moon. As the Moon continues on its revolution about
the Earth, it slowly, but surely, turns its dark side to us. Exposing less
and less of its sunlit side. We call this the "waning of the moon."