Before I started this class, I figured that my morning routine was simple. However, after nine months of physics, it is not as simple as I once thought. The static shock from my car in the winter was habitual, and the coffee cup falling off of it was old news. However, physics has changed my perspective on my morning. Let me set the scene...
One morning, I miraculously woke up early on my own and thought it would be fun to curl my hair. As I went to plug the iron into the outlet, I remembered that it was safe to stick something into one socket, but not both at the same time because that would complete a circuit and cause a charge. I carefully plugged the appliance in, and my hair looked great.
Next, I went to start the car, but since it had just snowed, it had trouble starting. Luckily I knew that since it was cold, the wires in the car were less likely to carry current, and this was why no energy was getting to the engine. I tried starting it a few more times before it turned on, and then I proceeded to turn on the heat full blast.
As I was driving through my neighborhood, I thought about how the wheels in my car propel me forward. The outer rims of tires are longer, but complete fewer revolutions. The inner part of the tire is shorter in length, and therefore must complete more revolutions to keep up with the outer part. The outer part has a higher rotational inertia because it is harder to rotate. Likewise, the inside part has a lower rotational inertia because it can make revolutions easier.
Having completed the motor lab, it was a realization to me that in a nutshell, my car operates on a magnet and a current carrying wire. Although it is a bit more complicated, I think that its wild that a motor consisting of two materials can create something as complex as a car.
Now driving down the hill to Starbucks, I see that the light at the bottom of the hill changes to red. I'd better slow down if I don't want to crash! I put my foot on the brakes and remember that the force of friction is equal to the net force of the car. If my car weighed 2000N, then the ground is pushing back on the car with 2000N of force in order to make it stop.
Once I safely get to Starbucks and order my coffee, I set it on top of the car while I put my bag in the back seat. I sit in the driver's seat ready to go when a stranger yells, "Hey you, your coffee's on the car! It will fly off when you start driving!" Jokes on them, because I know that according to Newton's First Law, objects in motion or at rest will stay as such unless acted on by an outside force. Because the cup is at rest on the top of my car, it will fall directly below where it was sitting if I moved quickly.
Now in the car with my coffee, I remember to put on my seatbelt! They are extremely important because as Newton's First Law states, all objects in motion or at rest will stay as such unless acted on by an outside force. If I was riding in a car and got in a crash, my body would continue to move forward because I am inside the car. Luckily, seat belts act as an outside force that stops me from going through the windshield.
As I merge onto I-240, I realize that there isn't another car on the road which means that I can safely drive on cruise control for a few minutes. Just like the coffee cup at rest is at equilibrium, so is my car when at cruise control. There is no net force acting on the car, and it can go at the same speed forever without stopping (if gas didn't exist).
Finally I arrive at school, but no matter which way you drive onto campus, there is a steep hill that you have to drive up. Going up a hill is work because there is a vertical distance and a force. You cannot directly increase or decrease work, but you can change the distance or force by using simple machines such as pulleys and ramps.
I pull up to the day hall and sip some coffee. I get out of the car, and when I go to close the door behind me, I remember what we learned about force and lever arms the day before. Force and Lever Arm are inversely proportional, so if I tried to close the door close to the hinge, it would be difficult because the force is strong and the lever arm is short. This is why it is much easier to close doors by the handle so that there is less force.
Who knew that all of these things and more would be present during one 30 minute journey to school! Physics is everywhere- you can run but you can't hide! Actually, running involves physics because of action-reaction pairs, but oh well.
Monday, May 18, 2015
Thursday, May 14, 2015
Wind Turbine Post
Background
The concept that this project revolved around was Electromagnetic Induction. In the context of a wind turbine, the magnets interact with the current carrying wire, and change the magnetic field. This induces a voltage and causes a current which results in a torque in the water bottles. Energy is conserved in the generator. All generators start with mechanical energy, but later produce electrical energy. (friction) (newtons laws)
Materials and Methods
Most of the materials we used can be found at CVS or a grocery store, and we only used two from our teacher. We bought a foam board, low grade washers, and a plastic water bottle that had no curves. We were provided with magnets, wire, electrical tape, and a hot glue gun.
(photos)
Results
The most difficult obstacle we faced was the coiling of wire. We had no problem making sure that they were all in the same direction, but we wound them too tight and had issues getting them off of the cardboard. We also learned that no amount of tape is too much. We secured everything with electrical tape so that it would not fall apart, it worked well. Don't focus on having a pretty wind turbine because ours was pretty special looking and it worked. I would advise future physicists to build the generator first and make sure that works. Then, add the framework because that does not matter as much. Make sure that you have all of your materials handy because while it may take a day or two to build one part, other parts may be built quickly. I would have done this because we were a little crunched for time, and were unable to progress quickly because we didn't have everything together from the beginning.
The concept that this project revolved around was Electromagnetic Induction. In the context of a wind turbine, the magnets interact with the current carrying wire, and change the magnetic field. This induces a voltage and causes a current which results in a torque in the water bottles. Energy is conserved in the generator. All generators start with mechanical energy, but later produce electrical energy. (friction) (newtons laws)
Materials and Methods
Most of the materials we used can be found at CVS or a grocery store, and we only used two from our teacher. We bought a foam board, low grade washers, and a plastic water bottle that had no curves. We were provided with magnets, wire, electrical tape, and a hot glue gun.
(photos)
Results
The most difficult obstacle we faced was the coiling of wire. We had no problem making sure that they were all in the same direction, but we wound them too tight and had issues getting them off of the cardboard. We also learned that no amount of tape is too much. We secured everything with electrical tape so that it would not fall apart, it worked well. Don't focus on having a pretty wind turbine because ours was pretty special looking and it worked. I would advise future physicists to build the generator first and make sure that works. Then, add the framework because that does not matter as much. Make sure that you have all of your materials handy because while it may take a day or two to build one part, other parts may be built quickly. I would have done this because we were a little crunched for time, and were unable to progress quickly because we didn't have everything together from the beginning.
Tuesday, May 12, 2015
Unit 7 Summary- Magnetism
One of the big ideas in Unit 7 was Electromagnetic Induction. We learned about commercial applications like how credit cards work, how traffic lights work, and what goes on in those pesky TSA check points. As an overall rule in this unit, we had to understand that a change in magnetic field induces voltage and causes a current. This was fairly easy to apply to traffic lights and credit cards, but more difficult to use it when understanding generators and transformers. A generator's goal is to generate current, but there are various components that must be present for it to work. Generators work opposite of motors. A magnet passes through a loop of wire, changing the magnetic field, inducing a voltage, and causing a current. It first uses mechanical energy to spin something over coils of wire, but then changes to electrical because of electromagnetic induction. Transformers are a simpler concept, but have a few qualities. There are step up and step down transformers which allow the right amount of voltage or current to pass through and get power to a destination safely. Important formulas to remember are P-primary= P-secondary, Iv=iV. Because of this, power is conserved. By using AC current in the primary, the magnetic field in the secondary changes. Also, #loops primary/v primary= #loops secondary/v secondary.
Our second big theme was Forces on Moving Charges. Regarding cosmic rays, we learned that charges have to be moving parallel to the magnetic field to feel no force when entering the earth's atmosphere. If they are moving perpendicular, then they will feel a force from the earth's magnetic field, and will be repelled back into space. While this also pertains to Magnetic Fields, knowing that charges always flow from magnetic south to north inside the field. The right hand rule came up during this theme, and it should be noted that I-index finger-current, M-middle finger-magnetic field, and F-thumb-force. When solving problems, using this right hand rule is important to determine where the missing value is pointing. In class, we assembled small motors consisting of a battery, a magnet, paper clips, rubber bands, and a coil of wire. This electrical energy turns into mechanical energy. The current carrying wire feels a force in a magnetic field and causes a torque which causes the motor to spin.
Lastly, we discussed magnetic fields which flow from magnetic south to magnetic north. The source of all magnetism is moving charges. There are spinning electrons that are clustered into domains. The electrons can be unaligned, where the electrons are pointing in all different directions or they can be aligned where they are pointing in the same direction. Back in Chemistry, we learned that opposites attract, and like charges repel. To go further, like charges repel because the direction of the field lines are opposite directions, and they push against each other. Likewise, opposite poles attract because the field lines are going in the same direction.
Our second big theme was Forces on Moving Charges. Regarding cosmic rays, we learned that charges have to be moving parallel to the magnetic field to feel no force when entering the earth's atmosphere. If they are moving perpendicular, then they will feel a force from the earth's magnetic field, and will be repelled back into space. While this also pertains to Magnetic Fields, knowing that charges always flow from magnetic south to north inside the field. The right hand rule came up during this theme, and it should be noted that I-index finger-current, M-middle finger-magnetic field, and F-thumb-force. When solving problems, using this right hand rule is important to determine where the missing value is pointing. In class, we assembled small motors consisting of a battery, a magnet, paper clips, rubber bands, and a coil of wire. This electrical energy turns into mechanical energy. The current carrying wire feels a force in a magnetic field and causes a torque which causes the motor to spin.
Lastly, we discussed magnetic fields which flow from magnetic south to magnetic north. The source of all magnetism is moving charges. There are spinning electrons that are clustered into domains. The electrons can be unaligned, where the electrons are pointing in all different directions or they can be aligned where they are pointing in the same direction. Back in Chemistry, we learned that opposites attract, and like charges repel. To go further, like charges repel because the direction of the field lines are opposite directions, and they push against each other. Likewise, opposite poles attract because the field lines are going in the same direction.
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