*A current carrying wires feel a force in a magnetic field and that force causes a torque; that's how a motor works.
I built this contraption to allow the wire to spin freely on its own. Each part of the device serves an important purpose.
Battery - supplies voltage that supplies current
Magnet - supplies magnetic field that makes charges move
Paper clip - allows rotation of the wire while also conducting current.
Motor loop (wire) - spins as a result of the flowing current
*I scrapped the paper clip (at the point where the wire sits on the paper clip loop *at the same point on each side*) to allow the current to flow through the wire, because otherwise the coating on the wire would get in the way. If you don't scrap the wire in the same place and on the same side on each end of the wire, the wire won't make a complete circle when spinning.
The wire spins because of moving charges. The magnetic field is going up towards the wire, the current is flowing across the wire, and thus the force is going to the side of the wire. That felt force creates a torque, so the loop spins.
All moving charges feel a force in a magnetic field if they are moving perpendicular to the magnetic field.
*This is why the equator is generally shielded from cosmic rays entering, and the northern countries aren't.
This motor could be used as a cake mixer. You could attach whisks to the motor loop, and then when you turn on the current, the wires will spin thus creating a cake mixer with the whisks spinning.
A charge is an unbalanced number of protons and electrons. If there is more positively charged particles than negatively charged particles or more negatively charged particles than positively charged particles, then the charge is unbalanced; it is either more negatively or positively charged.
There are two types of charges: contact and friction.
Induction is a way to charge something without touching it.
Electricity is energy being carried by charges.
Why does your hair stand on end when you take a winter cap off?
The cap steals e- from your hair though friction, making your hair become (+) and the hat (-).
Like charged repel each other, so the hair strands repel each other and stick up.
Why do clothes stick together in the drier?
Positive and negative charges are present when there is friction. When there aren't drier sheets in the drier with the clothes, the clothes will stick to each other because they are transferring electrons to each other. BUT when there are drier sheets, the clothes don't stick to each other, because the drier sheets steal e- from the clothes, making the sheets (-) and the clothes (+). Then the clothes are all positively charged, and like charges repel each other so the clothes don't stick to each other.
How does lightning work?
Clouds rub up against each other and become (-) though friction. This induces a (+) charge on the ground structures. The opposite charges will creep towards each other through the air, and if the path is completed energy will rush from the ground to the sky, and release light, heat, and sound in the form of lightning and thunder.
How do lightning rods protect structures?
Lighting rods are pointy and charges like to build up on pointy things. If the lighting strikes the rod it will channel the lighting around the house and directly to the ground. Since the charges are on the rod, the lightning will be more likely to hit the rod than the house and the house will be safe.
Polarization
An object is polar if the charges are separated (as in the ceramic bowl and balloon problems below)
A conductor lets charges move through the object.
An insulator stops charges from moving.
Why does plastic wrap stick to ceramic bowls?
As the plastic wrap is unrolled, it becomes charged through friction. When it comes over the bowl, the (+) charges in the bowl go toward the (-) plastic wrap because opposite charges are attracted to each other. The (-) charges in the bowl are repelled by the plastic wrap because they're like charges, so they move away from the wrap.
Coulomb's Law says F = kq1q2/d^2
and since the opposite attractive forces are closer in distance, the force between them is stronger than the repulsive forces, and thus the wrap sticks to the bowl. The bowl becomes polarized.
Why does a balloon stick to the wall after bring rubbed on your hair?
The balloon is charged through friction and become (-) when rubbed on your hair. When the ballon is brought close to the wall, the (+) charges in the wall are attracted to the (-) charges in the ballon, and then (-) charges in the wall repel from the like charges in the balloon, so the wall becomes polarized.
Coulomb's Law says F = kq1q2/d^2
and since the opposite attractive forces are closer in distance, the force between them is stronger than the repulsive forces, and thus the balloon sticks to the wall. The wall becomes polarized.
Electric Fields
An electric field is the area around a charge that can influence another charge.
The arrows show which way a positive charge will be pulled. In this case, the charge is going away from the other charge because they are like charges.
The arrows show which way a positive charge will be pulled. In this case, the charge is going towards the other charge because they are opposite charges.
The closer the lines are together, the stronger the electric field. Because of Coulomb's Law...
F = kq1q2/d^2
d = F
D = f
How does electric shielding work?
If you are inside a metal container, the charges will distribute evenly around that container. No matter where you are inside of the container you will feel no force from the electric field, because even if you're closer to a couple of the charges you are still further away from enough of them that you will feel no net force, thus your charges, electrons, and protons will all stay where they need to be.
Why are electronics placed in metal boxes?
Metal acts as an electric shield, so the electric field inside the metal zero (neutral), so the charges in the box won't be pushed/pulled by outside charges. The charges distribute evenly within the box as the are constantly moving. All the charges in the box will have equal and opposite forces in all directions. Because of the electric shielding, the sensitive electronic equipment inside of the metal that relies on the movement of charges, since it's running on electricity, is not going to feel a force inside that metal box. If the electronic equipment wasn't inside the metal box, it would feel a net force and then the device wouldn't work anymore, because it would be forced out of position and the charges wouldn't be where they needed to be.
Why can't your flash work continuously?
Capacitors are how flash works. Two oppositely charged plates that aren't connected continually add charges to each side and increase the electric field and energy between them. When the plates are connected briefly, the energy rushes from one plate to the next, and the energy is released as light thus the flash (cameras). It takes time to build up the charge on the plates and enough stored energy in the field, so flashes can't be used continuously.
Electric Potential
Electric potential energy is the energy the particle posses by virtue of its location. The stored energy in electric fields.
Electric potential is the electric potential energy per unit charge --> electric potential = PE/q
*measured in volts (V)
*electric potential does not equal electric potential energy
volt = joule/coulomb
Current is energy being carried by charges (energy flow)
*measured in amps (A)
*current = I
*more current = more/faster movement
Voltage is the difference in electric potential which causes current.
*Current and voltage are proportionate.
V increases = I increases
V decreases = I decreases
How to increase the resistance of an electric wire.
How to decrease the resistance of an electric wire.
According to Coulomb's Law, distance and force are inversely proportionate.
If the distance is doubled, the force is 1/4.
If the distance is halved, the force is 4x.
*Remember that we never manipulate the force, only the distance.
*If you double both charges in Coulomb's Law, the force will remain the same.
How can something have a higher voltage, but not be as dangerous as something with a lower voltage?
A high voltage, but a low energy.
--> safer
A low voltage, but high energy.
--> more dangerous
Circuits
Power = brightness measured in watts
P = IV
AC current = back and forth movement; electrons constantly dancing (plugs)
DC current = one direction moment (batteries)
Series Circuit
--> increase in resistance
--> decrease in current
*Will draw out less current than a parallel circuit would, because
Parallel Circuit
--> decrease in resistance
--> increase in current *Will draw out more current than a series circuit would, because
Why don't birds get harmed when they stand on a wire, but would get harmed if one ran into both power line wires with it's wings?
If a bird is sitting on a wire (just one) then there isn't a complete circuit. If the bird touches both wires with it's wings then there is a complete circuit. In a complete circuit, there is a difference in electric potential and that difference causes current to flow through the bird. If there isn't a complete circuit, there won't be a difference in electric potential, so the current won't flow through the bird and it will be safe.
Why does connecting a dead battery with jumper cables to a working battery with the car running make the battery work?
When the two batteries are connected, it creates a complete circuit so the energy can be transferred from the working battery to the dead battery. This will create a difference in electric potential and will cause current to flow (even though they always have the same amount of current) so the dead battery will then work.
Why are electric wires so thick?
Being thick is a way to decrease resistance. Since resistance and current are inversely proportionate due to I = V/R when resistance decreases, current increases. So if the wire is thick the resistance will decrease, increasing the current. If the device was a lightbulb, it would shine brighter because the current had increased.
Why is it dangerous to plug American appliances into European circuits?
American appliances are used to less voltage, and they also have a lower resistance which increases current. So when the American appliance is plugged into a European outlet, there is a higher voltage than the American is used to along with the high American current. Current is increased and high current plus high current is dangerous, because it could start a fire.
Why do lightbulbs typically burn out when they are immediately turned on, but not when they have been on for a while?
When the lightbulb is just turned on it's cold, and cold is a factor that decreases resistance. When resistance is decreased, current increases and a high current breaks the old filament in the lightbulb. When the lightbulb has been on for a while it is hot which increases the resistance and decreases the current, and a lower current won't break the filament like the higher current will.
How does a fuse/circuit breaker protect your house?
A fuse stops the current flow when it (the fuse) gets to be a certain degree of heat, when too much current is drawn from the wall. When the current gets too high, the fuse will burn breaking the fuse, cutting off current flow to all devices, so the wires don't cause a fire. A fuse is only added to parallel or parallel/series combined circuits, because they each branch of the circuit is individually power sourced (what your house has). Too much current = hot = possible fire = dangerous
