Ten Favorite Things about Physics

One: Inertia

 My favorite concept is Inertia. Inertia is NewtonsTthird Law which states that any object, whether in motion or at rest, will continue doing what it is doing. I thought this was amazing because I thought everything just started at a rest state where there not going and that when we push something we apply energy to the object making it move. I thought that this energy would be used up (in the form of heat) and when it ran out of energy it would stop. But mass doesn't act like a car, instead it's outside forces that do the stopping and starting 

Two: Newton's Second Law of Motion. 

Newtons second Law explicitly states that an object's acceleration is directly proportional to the net force acting on it and indirectly proportional to the mass. I really like this mainly because it was one of the simplest and easiest examples to understand in physics. It makes sense that the more force you put on an object the more it will accelerate (or "decelerate" due to an opposite force). And it also makes sense that the more mass something has the harder it will be to push it. It's much easier to push a small child than a large man. 

Three: Newton's Their Law of Motion 

This concept blows my mind, but makes tons of sense at the same time. Newtons Third Law states that to every action there is an opposite and equal reaction. No wonder I don't just break through a chair when I sit on it, because it pushes back on me (I guess the creaking noise when a large person sits in a chair is the chair actually pushing back).It would also be nice to say that if I hit someone then that person hit me also and the ensuing fight is just as much his fault (though that wouldn't get passed the headmaster). I guess thats why I would have bloody knuckles after the fight, because my opponent was hitting me right back.

Four: Systems 

Another smaller concept that I really like is that a force acting inside of a system doesn't do anything to the system. Only an external force can cause something to move or slow down. A person can't stop him or herself from falling through the air without a parachute and we also need to push on the floor in order to move. 

Five: Tangential vs Rotational 

Tangential velocity is the linear velocity (how fast a spot on a wheel is moving at any point) and rotational velocity is how many rotations a circular object takes. I thought it was especially interesting that a point on the outer part a circle has to move faster (have a higher tangential velocity) In order to keep up with a point closer to the center of a circle. It's just strange thinking one part of an object is moving faster than the other. 

Five: Lever Arm

In a way I always knew, but never realized, that the longer something is the easier it will be to move something else with it. Working with my Dad on projects at home we would always use a longer wrench for more stubborn bolts but I never actually thought about why that made things easier. Because the work formula is W=F times Lever arm the longer lever arm you have the smaller the force if you want to do the same amount of work. "Physics makes good sense" (Paul G. Hewitt).

Six: Centrifugal Force. 

First centrifugal force isn't real, it is merely the name we give to the inertia of us wanting to stay going in one direction while a centripetal force pushes us closer to the center of a circle. I thought that was really cool because I have felt the force of a car pushing against me as I go around a turn. Now when I sit in a car I actually know why my body hits the car door.

Seven: Gravity 

At every moment we are being pulled down towards Earths core and if it wasn't for Newtons Third Law we'd all be screwed and fall straight towards the center of the Earth. This is do to the fact that  every single object (that has mass) attracts other objects. and so we are attracted toward the center of earth. So if a girl says she doesn't find me attractive, i'll know physics says otherwise. 

Eight: Satellite Motion

Thanks to a combination of gravity and inertia we have satellites. If an object is moving fast enough around earth than it will not fall towards earth because it's inertia will keep it going in a linear path, but if it is close enough than gravity will still have an effect causing that linear path to turn and curve around the earth. So in reality satellites (and astronauts) are all in free fall and inertia is the only thing keeping them safe.

Nine: Magnets 

Magnets are amazing. The thought that some invisible force can actually interact and pull or push a force. I thinks it's really cool how magnets repel each other. Because field lines move from north to south (outside the magnet) and south to north inside if you put a south to a south or a north to a north the field lines oppose each other and actually push each other away. But if a North and South are in close proximity their field lines are going in the same direction and so attract. 

Ten: Energy Conservation 

Perhaps one of the simplest but still amazing concepts is that no matter what happens energy is always conserved, Energy in= Energy out. When using electronics or using your very own body you expend energy, but that energy doesn't just disappear it just takes on a different form. Ever touched a computer that's been on for a long time? Feels hot doesn't it, heat is just energy in it's simplest form (think of the sun). Other things such as the noise is also another form of energy. Energy in = energy out, it is always conserved. We can neither create nor destroy energy, just change it's form.

Wind Turbine Reflection

Making a Wind Turbine  

Section 1: Background 

The most basic concept about this lab will be taken from the from our studied of magnetism. We know that as a magnet passes through a coil of ferromagnetic material (like copper or silver) it produces a voltage. But the way voltage is induced is by a change in the magnetic field. The wind turbine provides this change.  

Section 2: Material and Method. 

To create this we needed some pipes in order to create a base. after that we tied some copper wire together in order to create the coils of wire. We used a hollow pipe at the top of the base in order to put a cylinder with batteries on it so that it could spin freely between the coils of wire. This cylinder is attached to the rotor of the turbine so that it spins. We placed four magnets north to south opposite each other so that they could create a changing magnetic filed as the turbine spins them. Inside the base we placed two wires down and had them exit through terminals so that we could complete the circuit for the current to flow.  

Below is a picture of a turbine like my teams.

 

Example of magnets and copper wire used.                                                                                                      

Section 3: Results and Discussion.  

The biggest factor to inducing voltage is making your propellors spin fast, the faster they spin the more change in magnetic field and so more voltage. In order to do this you need big (but lightweight) propellors that also have to be curved slightly so that the wind can push it sideways instead of back. If you use more than one magnet make sure they are far enough apart or else if they are strong enough they may break out of whatever you bound them with and attach together. Also make sure your magnet (or whatever their attached to) can fit into the coils of wire because if they can't, your screwed.

Below is a video our actual turbine working. You can stop it at 0:31.

Unit 7 Reflection

Unit 7 Reflection:  Magnetism

Magnets 

Moving charges produce a magnetic field. A domain is what we call a group of atoms whose electrons are all spinning in the same direction. When all of these domains are aligned is when an object becomes magnetized. Because all of these domains are now aligned they all point in the same direction. This is what creates the north and south poles. The charge always goes north then circles around the magnet into the south side and then up through the magnet to the north side again.  

In the picture above you can see what are called field lines. These are the magnetic charges that go throughout the magnet. As you can see when the north end meets a another north end they actually hit against each other and repel, the same goes for the south end. If you put a north and south pole next to each other the field lines go from the north side to the south side because their domains are facing in the same direction.

Horseshoe and refrigerator magnets are often called permanent magnets because of their lasting magnetic fields. However no magnet is truly a permanently magnetic, just as domains are aligned they can be unaligned. This can happen through a number of ways. Heat causes domains to be unaligned as well as simply hitting a magnet hard enough can jostle the domains. 

 Magnetizing a paperclip 

How can we magnetize a ferromagnetic material that is not magnetic, like a paper clip? First we need a magnet. A paperclips domains are all random, their all pointing in different directions and so cancel each other out. A magnet has a magnetic field because it's domains are aligned. When you bring the paperclip close the domains are attracted by the magnet and become aligned with the magnetic filed. The paperclip now has a north and south pole. The opposite pole of the paperclip is now attracted to the opposite pole of the magnet.

Earths Magnetic field 

Earth is a giant magnet. It has a north and south pole, but the geographic north pole is actually the magnetic south pole. This is why the north side on a magnet is attracted to the north pole. 

Cosmic Rays, Northern lights and Compasses. 

A charged particle moving through a magnetic field will only experience a force if it is moving perpendicular to the field. 

Cosmic Rays:  

 Every day the earth is being bombarded by particles (protons, electrons, photons) called cosmic rays. Due to earths magnetic field these particles are swept up, because they are moving perpendicularly with the field, which causes them to spiral towards the earths poles. 

Northern Lights: 

As the rays that travel along earths filed lines are brought to the poles they interact with the atmosphere creating auroras and other such things.  

Compasses: 

A compass is a tiny magnet allowed to swing around freely on a stick. Because of this it is affected by the earths magnetic field and when it is perpendicular to the field then it experiences a force that pushes it to be parallel with the filed lines and point north and south. 

 

Transformers

A transformer is a device that carries electric charges across empty space. They does by placing two coils of wire next to each other. By giving current (and an magnetic field) to one the other has a voltage induced to it. The coil that has a charge is called the primary, the coil that feels the voltage is called the secondary. It is important to note that voltage is only induce into the other coil only if the magnetic field is changing. This is why DC current will not work on a transformer, because it supplies a steady stream of current. Whereas AC switches back and forth constantly so the field is always changing. In a transformer the amount of coils (or turns) creates more voltage. If the primary has 10 turns and the secondary has 20, then the secondary would have twice as much voltage. This type of transformer is called a stepped up transformer. A transformer that has less secondary turns than the primary is called a stepped down transformer. This is how in a power line the voltage can be stepped up at the power plant and then sent long distances, then stepped down at a site closer to your house. This is similar to laptop chargers who use a step down charger in order to power your computer. Th
e wall socked may have 220 volts but the transformer in the charger pushes the voltage down to around 120 volts.

Equations 

Following these are the equations for the transformers: 

For voltage, turns and to show energy is conserved.

Primary Voltage/ No. of Primary Turns = Secondary Voltage/ No . of Secondary turns 

                                                                             or 

V(p)/Turns(p) = V(s)/ Turns  

Power is conserved equation 

PowerPrimary = PowerSecondary 

Voltage and current 

Primary Voltage X Primary Current = Secondary Voltage X Secondary Current or (VI=VI) 

Coils and Credit Cards 

We now know that when a magnet or a coil move near each other a voltage is induced. Some people found out that this could apply to how we spend money. A credit card has a strip of different magnetic charges along it (this forms the code). The credit card machine has a coil inside of it and as the magnetized strip of the card moves by it, voltage is induced which is then registered by the machine and interpreted as a code.

Motors and Generators 

Because It is much more practical to spin a coil inside a magnet, most people spin the coil to produce voltage. This arrangement of moving a coil in a stable magnetic field is called a generator. A motor is basically the exact opposite of a generator except instead of using mechanical energy to produce electrical energy, it uses electric energy to produce mechanical energy.

        A simple motor/ generator.

A simple generator/ motor.

Electric Currents and Magnetism 

As a wire carries a current, a magnetic field is produced. But if this wire moves through a magnetic field it feels a deflecting force and it will be pushed. If the wire's current changes directions than the force will also reverse. As we know the force is strongest when the current is perpendicular to the magnets. 

Heres the link to a video showing a simple motor: 

https://www.youtube.com/watch?v=O2oDaILnaoM 

How a Motor Works.

Motor Blog 

Parts: 

1. The Battery:  The Battery stores and provides the electric energy for the engine. 
2. Coil of Wire: The coil of wire is meant to carry the current through the motor 
3. Paperclip: Connects the battery to the wire and carries current. 
4. Magnet: THe magnet is responsible for pushing the coil of wire in circles so that it creates energy. 

The Armature 

The ends had to be scraped so that current could flow, but we scraped one fully and the other only partially. We did this so this because if there was a steady flow of current through the wire the coil would not turn all the way around but would turn backwards after one half turn.

Why the Motor turns  

First current flows from the battery up the paperclip into  the coil of wires, back down the other paperclip and back into the battery. The loop itself turned because the magnet field produced by the magnet applies a force up at the coil of wire. The loop had to be vertical so that it the force from the magnet could hit the coil vertically or else there would be no torque. This is do to the right hand rule, the electric current flowing throughout the coil give it a charge. The magnetic field, from the battery, is positioned perpendicularly from the coil and so the force from the magnetic field causes the coil to spin. 

Purpose:

The motor itself has no real practical purpose because its very fragile and doesn't produce a high amount of electricity. However it is a good example  of how a motor works. The only real application it has is to give students an example of electromagnetism. 

Link 

Heres a nice little video of my groups own motor.

Unit 6 Charges and Electricity

Unit 6 Reflection Charges and Electricity 

Equations you should know 

Coulomb's Law 

F=K*q1q2/d^2 

Ohm's law 

V=IR or I =V/R 

Power 

Power = current*voltage 

Voltage = change in PE / q 

Electric field = E = F/q 

UNITS 

F=Force 

V=Voltage 

A=Current 

I=resistance  

q=charge

Charge 

The central theme of this unit is something called charge, which is the imbalance of electrons and protons. Electrons and protons are both charged particles, electrons are negatively charged and protons are positively charged. How an object is charged is when it has two much or to little of either of these particles. An object is neutral when it has an equal amount of electrons and protons. 

Electrons are a little special in this relationship because they are much much smaller than protons. Because their so small (and their on the outside of the atoms nucleus). It is much easier for them to move from one electron to another.  

There are three ways that something can be charged: Contact, Friction and Induction. 

 Contact: When two objects touch and  transfer electrons from one to the other. 

Friction: When two objects rub together and one takes electrons form the other. Visualize taking off a beanie . Do the hairs on your head stand up, If they do than they are being repulsed because they are now positive. The beanie  had stolen some electrons form the hair making both charged. 

 Induction: The process by which an object becomes charged, first by being polarized form a charged object (that is by not touching it) and then touching the object with a a different neutral object allowing the flow of the opposite charges (those not being attracted by the charged object not touching). Now the   original object is no longer neutral and has a charge.

Voltage

One the first things that we learned in this unit was potential difference or voltage. Voltage is the difference between two points of electrically charged areas.  Think of a water pipe, one end has a bunch of water in it the other end has no water, naturally the water will flow from the filed end over to the empty end. This is an excellent example of how Voltage works. The most important thing to know is that Voltage is measued across two points, from the point it flow form to the point it's going to to. We can also say that it is the energy given to each Coulomb of charge. 

The equation of Voltage is change in potential energy over charge. (Potential Energy is the amount of energy a charge could have, it's measured in one point compared to voltages two) 

THe written equation is below: 

V = Change in PE / q 

or 

Volts (V) = Joules/ Coulombs 

Current 

Current is the charge that flows through the circuit from point a to point b. It's what Voltage pushes along. 

Current is measured in Amps. 

It's equation is Amps (A) = Coulombs/second 

or 

A = q/seconds  

current flows through the electrons in a circuit form one place to another. So if voltage is turned off  there is no current flowing.

AC/DC 

There are two different types of current. AC (Alternating Current) and DC( Direct Current). As the names imply AC is current that alternates meaning that it switches directions. flowing on way along the wire and then the opposite way a moment later. DC current is (as it's name implies) direct meaning that it doesn't change direction and keep going the same way. 

Resistance

This is what resist the flow of charge. Certain properties of a circuit will effect how easily a charge moves through it. The wider the wire the less resistance because the the electrons that flow though the wire constantly bump along the sides. The wider the side the farther they will go in without hitting a wall. Heat is another factor, the more heat you have the faster the electrons move. If you tried going through a room that had a bunch of people moving very quickly it would be pretty hard to get to the other side. So the higher the heat the higher the resistance. Also the longer the wire the more resistance the electrons will encounter because they will have a much longer way to go. 

The units for resistance are Ohm's 

Ohm's Law 

Ohm's law states that current that passes through a conductor is directly proportional to the potential energy.  

I =V/R 

or 

V= IR 

V = Voltage 

I = Current 

R = Resistance 

The Speed of Light 

Do electrons really move the speed of light? No. Electrons move excruciatingly slow, instead it is the Energy/electric field that moves so quickly. Energy merely passes through the electrons ( and nudges them a little bit) so that it can get form point A to point B. 

 The electric company pumps something into your house to make your appliances run. What is pumped into you house? Electricity! But what about the electrons, there already in the wires, there in the stoves, lightbulbs, toasters, dishwasher, act. THey are always there in fact they help make up those things. Their all cluster around other clusters of Protons in a huge atom sea. Even if you touch a power line the electrons don;t move very much (only a little bit) but it's the energy that hurts you and that passes through you. 

Coulomb's Law 

How do changes in distance affect force? 

Coulomb's Law or the inverse square law tells us that the closer the charge the stronger the force.  

The mathematical formula of this is written below. 

F = K*q1q2/d^2  

An excellent example this is the ballon problem described above (in friction). You you rubbed the hair with the ballon and it stole some electrons the ballon then became negatively charged. If you were to put that negatively charged ballon next to a wall it would do something called polarization where the negative charge of the balloon pushes the negative charges of the wall away but pulls the positive charges closer. The wall's net charge is still zero the charges are simply seperated. Now the negative charges are much closer to the positive charges and so have a stronger attracting force than the farther away and repulsive negative forces.

 

Coulomb's law is also called the inverse square law because distance and force are inversely proportional to each other. 

2d=1/4F 

1/2d=4F

Electric Shielding 

If you have say an Xbox and you want to keep it running well, then you will want to keep that metal box around it, because it serves a special purpose other than to just look good. THere is this thing that is called an electric field, everything from cars to VCR's have an electric shield. THis thing is a conductor that stops charges from entering a certain area and damaging the delicate things inside (I.e. humans, circuitry). It does this by distributing the charge equally over the conductor. If a charge is the same (positive on positive, negative on negative) then they would naturally repulse each other. So the positive or negative charge will push themselves away from each other and around the conductor. Now the charges are pulling on every single part of the inside of the conductor, which means that even if the inside is oppositely charged than the outside. The inside is still neutral. Even if you have a negative charge closer to one wall then the other. Due to Coulomb's law the outside charges closer to that inside charge pull harder than the charges on the opposite side. But there are more charges pulling the negative on the opposite side, so neutrality is conserved. 

The equation for electrical shielding difference is E=F/q

Power 

Power is the rate by which something does work. 

It's formula is Power = VI 

The units of Power are joules per second or the watt

Parallel and Series 

There are two types of circuits along current can flow, Parallel and series circuits. 

Series is the more simpler of the two. It's just a simple circuit with one or two light bulbs attached in side by side. Because of this current has only one pathway that it can pass through. The resistance of these bulbs is the sum of each individual bulb.Voltage is also evenly distributed amongst the bulbs so that if you add them up they would equal the voltage of the source. 

Each bulb                        Total 

V=12v                            V=IR

                                          =3(2)

                                          = 6v 

                                        

R= 2 +2                          R=2 ohm's 

  =4 

I = V/R                            I=I

  = 12/4                             =6v

  =3A  

Parallel circuits are when you take two or more bulbs and attach them so that each bulb has it's own pathway to the battery. This makes it so that if one bulb blows the other can still run because it will have it's own own full circuit to the battery. The total resistance in a parallel circuit is half the resistance of one of the bulbs. Voltage remains the same always (this is why it glows brighter than series). And the current of a bulb adds up to the total. 

the following is true about parallel circuits

Each bulb                          Total

R= 2ohm's                         R= 1/2 (2) =1 ohm.                                             

I = V/R                              I = V/R 

 = 12/2                                 = 12/1

  = 6A                                  = 12A

 

V= 12v                               V=12v

Fuse 

A fuse is a small device that is inserted on a circuit so that it can stop the flow of current if it gets to high. When the fuse gets to hot it will melt and stop the flow of current.

What I liked 

I really liked this unit because it was interesting to find out how electricity actually powers the things that we own. Like other physics units it's really applicable to everyday life and it's interesting to think about. 

What I would do better next time. 

I'm goeing to try and pay attention a lot more during labs, I often feel like I don't get very much done or I just don't know whats going on and so i'm left feeling confused.  

 

Ohm's Law resource

Here's a great resource for Ohm's law.I think it really helped me understand how voltage relates to Ohms law and also gives some good examples to make things clearer.

I thought this was great introduction video into voltage. It focuses a lot more on current than I feel we do, but it also gave some great analogies by using lakes and rivers that would be great for any beginner physicist.