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.