Unit 7

In this Unit we discussed about

1. Magnetism
2. Motors
3. Electromagnetic induction
4. Generators
5. Transformers 

Each magnetized object or moving electrical charge will have a magnetic field, which is a region that the force of the magnet acts. This is created by moving charges in an object and the symbol for magnetic field is b. Each magnet have a magnetic North and South pole, the magnetic field goes out from the Magnetic north and comes in from the magnetic south. Same pole magnets repel and opposite attract, this is because the direction of both magnetic fields are moving opposite each other, therefore creating a ball like space between the magnet. An object can be magnetized by aligning it's domains, for example when a paper clip attracts to the magnet the domains in the paper clips  follow the magnetic field of the magnet making the domains of the paper clip similar to the magnet. The paper clip will them become magnetized and allowed to pick up other paper clips. 

Motors are devises which change electrical energy into Mechanical Energy. It depends on a current carrying wire and a magnet. in order to cause kinetic energy it has to feel a force which causes a torque, this force must be perpendicular to the magnetic field.

Electromagnetic Induction is a change in the magnetic field that induces a voltage which causes a current.
Faraday's law:#of loops in primary/voltage of primary= #of loops in secondary/voltage of secondary.

Generators are completely opposite from Motor, they convert mechanical energy into electrical Energy. They work by constantly changing the magnetic field of an object, as the magnetic is mechanically turned continuously in the loop of wire, it causes the wire to change it's magnetic field, which induced a voltage and causes current. An example of that would be a wind turbine, as wind turns the blade, the blade  turns some magnets around a loop of wire causing a change in b and inducing a voltage causing current.

Transformers are devises that either step up (increase) or step down (decrease) the voltage. U t is made of a primary and secondary coil, As current enters th eprimary coil it's b affect the secondary coils b allowing it to induce a voltage. So if there are more wires in the primary than secondary then it steps down the voltage, if there is more loops in the secondary than the primary it steps the voltage up, but both cases Power stays the same.

Unit 5

In Unit 5 we managed to cover these topics:

1. Work and Power
2. Work, Potential Energy and Kinetic Energy Relationship
3. Conservation of Energy
4. Machines

 

1.The equation for Work is "work = force*distance", work is measured in joules and can only be present if the force and distance are parallel, for example A person going up the stairs would have work because both the force and distance are upwards, but a person carrying a glass and moving forward, no force is acted on the glass as the force and distance are perpendicular. Example if you weigh 50 newton and run up a 10 meter high stairwell,  50*10 = 500J

 

Power is how fast work is done and is measured in Watts, the equation for power is "power = work/time". Example if you weigh 50 N and run up a 10 meter high stairwell in 5 seconds, 50*10 = 500, 500/5 =100 Watts.

 

2. Kinetic energy is the measurement of the energy carried by a moving object, it is like work also measured in Joules as the change in Kinetic Energy is equal to Work. The formula for Kinetic energy is KE = 1/2m(v^2). How does an airbag keep us safe ?

You always go from moving to not moving weather and airbag is present or not. this means Kenetic Energy will be the same in both. Airbags only increase the distance it takes which decreases the force making you suffer less injury but the work is still the same.

Potential Energy is the energy of a position (height). The equation for Potential Energy is PE = mgh which is mass*gravity*height. PE can be present while an object is at rest or moving. Potential energy can change into Kinetic energy when it goes from falling to hitting.

 

3. Energy Cannot be created nor destroyed they simply convert from one form to another, this is called conservation of energy. Example in Newton's cradle as one ball is lifted you just put some potential energy in it, when you release the ball and it hits the other balls the energy is converted from potential to kinetic energy, as the ball from the other side pops up it converts back again into potential energy and so on.

 

4. Machines use work to operate, the work in always equals the work out. A machine works by increasing the distance thus decreasing the force needed to move the operate the machine, but the work always stays the same. Example: Xavier lifts a 200N box up into a truck that is 1 meter high from the ground and uses 200 Joules of energy to do so. Gannon on the other hands is smart and uses a 3 meter long ramp to push his box up,  his work will also be 200Joules but because the distance is 3 then the force = 67 which is way easier than what Xavier did.

 

 

10 physics moments

Physics moments in Switzerland 

1. In the Summer we decided to go to the top of a mountain and jump of a cliff with a parachute, so we jumped on the car and started heading up the mountain. I told my brother to put on his seat belt so that he does not shoot out from the car if we had to press the break, he laughed and said "how will I shoot out, it doesn't make sense". I explained to him what Newton' first law was, "An object in motion or at rest, will stay in motion or at rest unless affected by an outside force", So if the car stops, your body will continue to move forward which is explained in Newton's first law and you will shoot out of the car. But if you are wearing a seat belt, it acts as the outside force and stops you from shooting out. 

2. In the car, my smaller brother punched me in the arm and got hurt, he exclaimed: "how did I get hurt if I punched you", I replied by saying that "every action has an equal and opposite reaction" Which in Newton's 3rd law. So i continued when you punched me with a force, my arm gave that exact same force right back at your fist causing you to get hurt. 

3. a few minutes before our arrival my father saw a electrical wire leading to a huge box, he exclaimed "I wonder what these boxes are". I immediately responded that these where transformers, they step down the voltage in the power line. He asked how does it do that, I answered by saying that a transformer is made of a primary loop of wire carrying Alternate current which induces a voltage on the secondary loop of wire. I added by saying if you want to step down the voltage you have more loops of wire in your primary than in your secondary, and also when the voltage decreases the current increasing therefore keeping the power equal all the way through.

4. As we arrived at the peek of the mountain we found a group of people playing tug of war, I joined the losing team and told them don't use your arm to pull, but only to grab the rope and use your legs to push yourself backwards. A person answered by saying why. I replied by stating that when you pull with you arms, they just pull with the exact same force back at you, Newtons 3 law explains this "Every action has an equal and opposite reaction". But when you push forwards on the ground it responds with an equal and opposite reaction propelling you backwards. We tried it out and ended up winning the tug of war. 

5. We got suited up for the cliff jump and I was the first one to go, I jumped off the cliff and before reaching the terminal velocity I was forced to open the parachute as I was getting closer to the ground. I felt a thrust upwards as soon as I opened the parachute. I thought to myself this is because my f air increases dramatically due to the increase of my surface area, this caused my net force to be upwards as the f air was greater than the f weight, A few seconds later I stopped slowing down and realized that I was going at constant velocity, I knew that I reached my second terminal velocity as my f air is now equal to my f weight, so I am not accelerating upwards or in any direction anymore. 

6. After completing a fun day in the mountain, we decided to head back to the hotel, I entered my hotel room and suddenly all the electricity in the hotel was cut. I ran down to the lobby to ask what happened and they told me a fuse broke, 2 minutes later the electricity was back on, my brother asked how do they replace the wires that broke that fast. I replied by saying, none of the wires where affected due to the fuse, I added by saying the hotel is wired as a parallel circuit and not a series circuit so that each appliance can get the needed amount of current, not like the series circuit where all the appliances split the current available making them preform poorly. The fuse is placed at the beginning or end of the circuit, I expanded, as encase of too much current entering the wires the fuse would cut the hole circuit allowing no harm done to the wires, and the fuse has to be physically replaced. It is just made of a piece of wire that is more sensitive to current overload than the wires in the circuit.

7. In the Hotel, I decided to go to the shop downstairs and bought a swimming suit for my small brother. As I paid with my credit card asked, when your credit card is swiped, what is happening, how is the money taken? I answered him by saying that, first a card has a magnetic strip on it and the machine has loops of wire in it, so when the strip of magnet passes through the wire, the change in magnetic field of the wire induces a voltage in the wire which causes a current, as long as the magnetic field is constantly changing, the current then sends a signal to accept or decline the card.

8. My brother and I went back up to the room and I grabbed the phone charger and plugged it into the socket, he asked "Why does the phone charger have a small box?" I replied by stating that the box is a transformer. It is used to step up or step down the voltage needed for the device to work. I added by saying that a transformer has 2 separate coils of wire. AC is going through the primary wire, which causes a change in the magnetic field of the of the primary thus changing the secondary coil. This induces a Voltage into the secondary coil which causes a current, if the primary loops are more than the secondary then it is a step down, (voltage goes down), if the secondary is greater than the primary then it is a step up (voltage goes up).

9. My brother then plugged in his X-box which he had bought from America, and as soon as he turned it on the X-box made a huge bang sound and started smoking, my brother freaked out and asked me what happened. I started by saying that the current that comes out of the socket in Europe is greater than the current that comes out from America. Appliances in America are made to have a smaller resistance, due to the smaller current taken from the socket, So when you plug in an American appliance in Europe the small resistance receives a great current which causes the wires to burn and destroys the device.

10. dinner time was coming and we headed down to a restaurant, on the way we spotted a wind turbine and my brother asked how does it work, I replied by saying as the wind turns the turbine it causes magnets to rotate inside a loop of wire, which then changes the magnetic field of the wires thus inducing a voltage and causing current. This turns mechanical energy to electrical energy

Wind turbine

Section 1

Energy conservation: A wind turbine is a generator that turns mechanical energy into electrical energy by using the force of the wind, to generate the generator. The generator consists of loops of wire, magnets, blades to spin the magnet inside the loops of wire.

 

Electromagnetic induction: In a generator when magnets spin close to the loops of wire, the wire feels a change in the magnetic field which then induces a voltage which causes current to be flowing in the wire.

 

Newton's first law: "An object at rest will stay rest and an object in motion will stay in motion unless acted by an outside force" the blades started out stationary, so they remained that way, and the wind (outside force) blew it caused the turbine to start turning.

 

Newton's second law: "acceleration = force/mass" When my group where setting up the blades and testing on how powerful the fan was, we took the mass of our magnets into account. We wanted to make sure that we had a small mass for the magnets so that our acceleration can be greater, because we had no control in increasing the force, as the fan had an equal force for everyone.

 

Torque: As the wind blows on the blades, it causes a torque on the blade, which causes it to start spinning and therefore spinning the magnets as well and generating electricity.

 

Friction: This step is important to setting up a wind turbine as if you have a lot of friction, most of the energy you are capturing from the wind will not be exerted into spinning magnets, but it will be lost throw friction, therefore efficient and little friction is important

 

Section 2

 

To reproduce the design we used, all you need will be:

 

• 6 pieces of 10cm*8cm thin wood
• 2 rods, one metal one wooden, thin metal one
• gun glue
• 8 small lightweight magnets
• 2 plastic cups
• 3-5 meters of wire

Firs you construct a box from 4 of the wooden pieces and drill a hole in the middle of them and put in the wooden rod, then cut 2 one cm pieces out of the metal rod and sick them on complete opposite sides of the wooden rod, then connect 4 magnets on each side, zip tie the metal rods so that u secure them. Next rap the wire tightly on the outside of the box. Then cut the 2 cups in half and glue two on each side of the rod to pick up wind. Finally elevate the box so that the turbine can spin without the blades hitting the surface it's on. it should look like this :

 

 

 

 

Section 3

Megan and I managed to generate 0.012 amps and 0.012 volts, we managed to get a trickle from the light bulb, but we never got solid light as it take 0.3 volts to light the light bulb, so we where far from close, but we still managed to get the highest reading in our class.

Section 4

This project made me actually be able to say to people I created electricity before. It made me be able to create an efficient generator, which I thought would have been impossible for me to do just a few months ago. I noticed when modifying my turbine, that when I had few big magnets on the turbine, it induced less voltage but when I replaced them with more small magnets, it increased my voltage by nearly more than double. If I was to do this project again, I would also make sure that the wires are tide up tighter around my box so, that it does not get caught by the blades. Also I would make sure to drill my hole for the rod, precisely in the middle and not at a slanted angle.

Motor Blog

A motor is a object which consists of a current carrying wire and a magnet.

The Motor that I created in class consisted of four parts as you can see in the picture below. The first part was the battery itself which provided the current for the circuit, the second where paper clips which where attached to both end of the battery completing the circuit with the wire and where holding the wire up. The third part was the looped wire which caused the rotatio, and the fourth was the magnet that was placed directly under the wire which from it's magnetic field allowed the wire to spin as it had current running through it.

The motor is able to spin because when the magnet feels a current running through the wire, it causes a torque which makes the wire spin. A torque is present due to the charges being perpendicular to the magnetic field, because of the way the wire was scraped which is not on the flat side of the loop but the bent side.

My motor can be used for any object that requires rotation such as motors in wind mills or drills. The exact one cant work but more efficient and developed one might be more suitable. 

Unit 6 review

Charges and polarization

There are 2 different types of charges. there are protons and electrons.
Protons are positively charged and electrons are negatively charged
Like charges repel and opposite charges attract.

Direct contact: This is when objects touch each other and charges transfer throughout to even out. An example is when a person touches you and manages to shock you, that is the electrons transferring.

Friction: when an object rubs against another object it steels electrons from it making one object have more electrons and the other with more protons. When you are wearing a ski cap and take it off, the cap steels electrons from your hair making it stick out and attract to the cap.

Induction: This is where you are able to separate charges from a neutral object without touching it. When you bring a negatively charged metal near a neutral object, the electrons will try and get further from the metal bar, while the protons want to get closer, then if you link the neutral object to the ground, the electrons will escape leaving the object positively charged. the process of separating the positive charges from the negative in a neutral object is called polarization.

Electric Fields

An electric field is a region around a charge that can push or pull another charge, as the object gets further from the electric field the influence is weaker. The reason why electronics are safe in a metal box is because the metal box creates it's own electric field which will not allow any other fields or charges influence the electronic device.

Electric Potential:

Electric potential is different than electric potential energy. Electric potential is voltage. An equation for Electric Potential is v= pe/q. which is measured in volts.
Capacitors are found in the camera's flash section.
The reason why the flash cannot go on continuously is because the capacitor has 2 oppositely charges plates which are charged, and as enough difference in potential energy is built between the 2 plates, they come in contact for less than a second causing the flash, then it has to charge up again for a couple of seconds until it can repeat the process.

Ohm's Law and Current:

Current can only be present in a complete circuit where electric potential difference is present therefore voltage is present. The two types of current are:

• AC current, where current vibrates back and forth in its same position
• DC current, where current moves in one direction

Current is directly proportional to Voltage and inversely proportional to resistance according to Ohm's Law, therefore I = V/R

Different countries has different amount of volts coming out of its appliances, therefore the object in that country have the resistance set for the according voltage it is supplied with, to produce the wanted current. So if an object that was created in America is plugged into a European outlet, the object will get destroyed as the resistance is low and the voltage is high, causing the current to be too much.

Circuits 

There are two different types circuits, the first one is a series circuit where all the appliances are linked together in one lane, and the more appliances are added the greater the resistance which affects all of the current running through the appliances. A parallel circuit is a circuit where the appliances have different lanes of wire therefore the more lanes you open, each appliance's current does not change, and the overall resistance decreases allowing to provide the full amount of current needed for each appliance. 

Homes are equipped with parallel circuits.

A fuse is usually put at the start or the end of a parallel circuit, so that if too much current is going through, where the appliances might be in danger a wire in the fuse will melt causing the circuit to disconnect, not allowing any current to pass by.

Mousetrap Car

Mousetrap Car

For the past 2 weeks my partner Luck and I have been working continuously on our car trying to figure out what we can do to make it work and how we are going to manage our time finishing it. 

Time: 4.38 seconds
Place: 1st

Newtons laws lays a major role in the performance of the car. 

• In Newton's First law he states, "An object at rest or in motion will stay at rest or in motion unless affected by an outside force". When the string was set up and launched, our car would  continue to move even after the rotation of the axis was over, this related to Newton's 1st law. 
• In Newton's Second law is ( a = F/m), so acceleration is proportionate to the force and inversely proportionate to the mass. In the mousetrap car how heavy the car was played a major role as if it was heavier the acceleration would decrease as it is inversely proportional. 
• Newton's Third law states that "Every action has an equal and opposite reaction" Relating this to the car, the when the wheels are pushing on the ground the ground pushes back making the car launch forward. 

The wheels of the car relied on friction so that all the rotation would be applied to the ground rather than the car turning in place because of the lack of friction on the wheels, Luck and I started with wooden wheels which had little friction, so the car started to skid on the ground and never caught friction on the ground. We replaced the wooden wheels with a discs that had rubber on the edges so that it increases the friction.

We started with small wheels which rotated extremely fast as it had a low rotational inertia, when we changed to big wheels, the car moved slower because it had a greater rotational inertia, but managed to cover the same amount of distance than the small wheels. As we increased the size of the back wheels, the discs had greater rotational inertia as it had a greater circumference, but also increased the rotational velocity as one rotation in this bigger wheel covered more distance than the smaller wooden wheel. So the bigger wheels finally made my car cover more distance and reach the finish line, and with our efficient structure we managed to get the fastest time.

When the trap in the car is pulled back potential energy is stored and as soon as the trap is set the potential energy in converted into Kinetic Energy making the car move forward. We cannot calculate the potential energy of the spring as the car looses lots of its potential energy to friction from the wheels and the axis or the friction from the ground, we also do not have the proper equipment to measure them. There is also no work done as the direction in which the spring is releasing is not parallel with the direction the car is moving.

Reflection:

The final design of our car changed dramatically from the original design, we planned on having the same size wooden wheels, but due to the car having no grip on the ground and just skidding while staying stationary, we decided to get bigger back wheels and have more grip on them, so that is why we switched the wooden wheels with discs that had rubber on its outside for grip. In the future I would be more careful in building my body and axis so they are not bent to one side, as our car was moving not in a straight line but at a curved direction which was frustrating, so if we had our car built so that it would not curve, we would have had a greater velocity.