Ch21_Magnetism

toc =CH21_Magnetism=

1.
OPTIONAL Gizmo: Magnetism. Go to the gizmo and click on "Lesson Materials", and either print or download the guidesheet needed to complete the Gizmo. Don't forget to do the 5 Online Assessment questions when you are done. (due 11/21)

2. Complete Ch 21 Guiding Questions [|NewVersion!], #1-14, on wiki. Use whatever sources you like, but make sure you credit them properly, __//on your individual wiki//__. (due 11/21)

> [] >  1. Describe magnetic poles and their characteristics.  2. Describe what is known about the Earth’s magnetic field.  3. What is a magnetic field?
 * NOTES FOR ALL GUIDING QUESTIONS COME FROM:**
 * **Class notes**
 * []
 * Magnetic poles are the two ends of a magnet that are oppositely charged. The magnetic force is directed from the 'North Pole' to the 'South Pole'.
 * The Earth's magnetic field is not actually at the top of Earth. This is because the Earth rotates along a slanted axis, with the North Pole at the top end of this axis and the South Pole at the bottom. It is also important to know, even though it's confusing, that the North Pole of Earth is magnetically the South Pole. Because of this the North end of the Compass Needle is attracted to the magnetically south Northern Pole.
 * a volume of space where there is a change in energy that affects outside charges within that space.

 4. Why does a compass point north?  5. How is the magnetic force on a charged particle measured? 6. What is the magnitude of net force on an electron moving in the magnetic field where //B// = 2 T, //v// = 4 x 104 m/s, and ø= 30o? 7. In the giant CERN particle accelerator in Switzerland, protons are accelerated to speeds of 2.0 x 108 m/s through a magnetic field of 3.5 T and then collided with a fixed target. What is the magnitude of the magnetic force experienced by the protons as they are accelerated around the giant ring? 8. How is the direction of magnetic force on a charged particle determined? 9. See animation and note your observations: HYPERLINK __ http://webphysics.ph.msstate.edu/javamirror/ipmj/java/partmagn/index.html __ 10. When a charge enters a magnetic field, what is the relative direction of the velocity and the magnetic force? 11. In what direction will a charge move when it enters a magnetic field? 12. How is the radius of this motion measured? 13. Go to HYPERLINK "http://physics.nad.ru/Physics/English/el.htm" **__ http://physics.nad.ru/Physics/English/el.htm __** (Look at the animation labeled “Motion of the charged particle in perpendicular magnetic and electrostatic fields.”) See animation and note your observations. 14. Go to **__ http://www.members.aol.com/judsonewagner/ __** (Click on __ charges within fields __ from E&M. Observe the right-hand animation.) See animation and note your observations.
 * A compass points North because the magnetic force on the planet causes the needle in the compass to be attracted towards the North, while the end of the needle that is not used is attracted to the South Pole.
 * Magnetic force on a charged particle is measured in Telsa's. It can be measured by many things, such as a balance if the magnetic force is directed upward or downward on the balance.
 * F B =q*v*B*sinø
 * F B =(1.6*10 -19 )*(4*10 4 )*(2)*sin(30º)
 * F B =6.4 * 10 -15 N
 * F B =q*v*B*sinø
 * F B =(1.6*10 -19 )*(2*10 8 )*(3.5)*sin(90)
 * F B =1.155 * 10 -10 N
 * The direction of a magnetic force can be found using the right hand rule, and knowledge of where the magnetic field and current are moving. Using your right hand, have your fingers face the direction of the magnetic field and your thumb in the direction of the current. The palm of your right hand is the direction of magnetic force.
 * [[image:Screen_shot_2011-12-06_at_8.29.13_PM.png]]When v=0 particle moves in a cycloid curve
 * [[image:Screen_shot_2011-12-06_at_8.30.15_PM.png width="206" height="101"]] As v gets larger, the particle moves in a trochoid spiral.
 * [[image:Screen_shot_2011-12-06_at_8.31.29_PM.png]]When there is no electric field the particle moves in a helix pattern.
 * The direction of the velocity will be in the same direction as when it entered the magnetic field, but it will be forced in the direction of the magnetic force, changing its trajectory to that direction as the charge moves.
 * When entering a magnetic field, a charge will move in the direction of the magnetic force.
 * Radius can be calculated using the equation B=(µ o *I)/(2π*r). In most cases, the radius is too small to measure with a meter stick or ruler.

3. Notes on 21.1 – 21.4 and Practice Right-Hand Rule. In class 11/18

4. Complete Ch21 ConceptQ #2,3 and Problems #7,9,10 //in HW Journal//. (due 11/21)

5.
Do AP Problem #2. [|AP Problems #1-13]. In class 11/18

6. Quiz on Capacitance In Class 11/21.

7. Practice problems with magnetic force on moving charge. In Class 11/21. 8. Do AP Problem #6. [|AP Problems #1-13][| __(due 11/28)__]

9. Complete Prelab questions for Magnet Lab __//on your individual wiki//__. (due 11/22)

**Pre-Lab Magnet Lab**
1. The objective is stated in the title. What is your hypothesis? As the distance from the source increases, the magnetic field strength decreases in a cubic relationship.

2. What is the rationale for your hypothesis?

This is the equation for magnetic field strength. There is an inverse cubic relationship between B (magnetic field strength) and the distance from the source.

3. How do you think you might test this hypothesis? We will use a sensor and magnets to determine that magnetic force at varying distances measured by a meter stick. By using the same magnet for each test and the same sensor, only changing the distance at small intervals, we are able to calculate the magnetic force at each distance and graph it. In the graph we should see the inverse cubic relationship expected in the equation.

4. Read the entire procedure through. ok

5. Design data table(s) in order to record your observations and calculations.
 * Constant (2*u o *u/4π) || Distance (m) || Distance Cubed (m^3) || Experimental Magnetic Field Strength (T) || Theoretical Magnetic Field Strength (T) || Percent Error (%) ||

10.
Do LAB: Magnet ([|Labsheet]), with Lab Analysis and Group Report ( In class 11/22, due 11/23)

11. Complete Ch 21[|Guiding Questions],#15-22. Use whatever sources you like, but make sure you credit them properly __//on your individual wiki//__. (due 11/23)

15. What is the magnitude of magnetic force on a current-carrying wire? 16. What is the direction of magnetic force on a current-carrying wire? 17. A 0.90 m long straight wire on board the Voyager spacecraft carries a current of -.10 A perpendicular to Jupiter’s strong magnetic field of 5.0 x 10-4 T. What is the magnitude of the magnetic force experienced by the wire? 18. If a 4.0 m long cord caries a current of 6.0 A, how large a magnetic force is created on the cord by the earth’s magnetic field of 5.3 x 10-5 T when it is perpendicular to the field? When parallel? 19. Describe how and why a current-carrying coil turns in a magnetic field. 20. What is the principle behind the design of motors and generators? //21. What is required in order to produce all magnetic fields?// 22. What is the direction of the magnetic field around a long straight conductor?
 * The magnitude of magnetic force on a current-carrying wire can be found using the equation F=B*//I*//L*sinø. It is the amount of force exerted on the current-carrying wire by a magnetic field.
 * The direction of magnetic force is part of the second right hand rule. In the second right hand rule, our fingers represent the magnetic field direction and our thumb is the direction of current. We pretend our hand is grabbing around the outside of the wire with the thumb in the correct direction. In this case, magnetic force, the palm, is always facing in towards the center of the wire.
 * F B =B//*I//*L *sinø
 * F B =(5*10 -4 )//*//(-0.1)*(0.9) *sin(90)
 * F B =-4.5*10 -5 N
 * F B =B//*I//*L *sinø
 * F B =(5.3*10 -5 )//*//(6)*(4) *sin(90)
 * The coil has its own magnetic field that acts with the initial magnetic field, creating a net torque which causes the coil to spin or rotate.
 * A motor is a device that uses current to rotate a coil, turning electrical energy into mechanical energy.
 * A generator does the opposite, as a mechanical energy spins the coil, generating a magnetic field and creating electrical energy that can be used or stored.
 * In order to produce a magnetic field you need current running through the coil, and a moving charge.
 * The direction of the magnetic field will be in a direction that is 90º from the long straight conductor.

12. Notes on 21.5 – 21.6 and complete Practice Problems: Kovalcin #121 #1, 2 a-c, 3, 4, 5, 6, 8. //In classwork notebook.// In class 11/23

13. Do AP Problem #10. [| __(due 11/28)__]

14. Complete Ch21 ConceptQ#10 & Problems #26,29,34 //in HW Journal//. __ [|(][|due 11/28)] __

15.
Notes on 21.7 – 21.8 with Practice Problems: Kovalcin #121 (2d, 3, 7) and #122 (8 – 13); #124 (6 – 8). In classwork notebook. In class 11/29

16. How does a motor work? In class 11/28

17. Complete Ch 21 Guiding Questions #22-33. Use whatever sources you like, but make sure you credit them properly //on your individual wiki//. (due 11/29) 22. What is the direction of the magnetic field around a long straight conductor?
 * The magnetic field goes around the conductor, and there is a second right hand rule to find out whether it is clockwise or counter clockwise.

23. How do you figure out the direction of this magnetic field?


 * The magnetic field around a long straight conductor is dependent on the direction of the flow of current. With your right thumb pointing in the direction of the flow of current, grab with your fingers around the conductor. The direction your fingers point are the direction of the magnetic field.

24. What happens if a long, straight conductor is wound into a long coil?


 * When a long, straight conductor is wound into a long coil of multiple loops, the strength of the magnetic force increases by the same multiple. The equation for magnetic strength is re-written as F=n*B*//I//*L*sinø, where n is the number of loops of the conductor.

25. What is Ampere’s Law? What does it mean? 26. What is the magnitude of the magnetic field of a long straight current-carrying wire? 27. If a single wire has a magnetic field around it, then what happens when there are two parallel wires close to each other? 28. Go to [] and click on induced B-fields in the E&M section. The right hand animation shows parallel wires, while the left shows a single wire.
 * Ampere's Law states that the magnetic field around a current is directly related to the electric current which acts as the source, just as the electric field is proportional to the charge which serves as its source. This means that the magnetic field strength is determined by the current of its source, and the electric field is determined by the current of its source. As the current gets stronger, the magnetic field strength or electric field created by it gets stronger.
 * The magnitude of the magnetic field of a long current carrying wire is small, and this is because the magnetic field is indirectly proportional to the length of the wire, as seen in the equation F=B*//I//*L*sinø, as the length gets longer, the magnetic field strength gets smaller if the magnetic force, angle, and current do not change.
 * Two parallel wires that are close to each other, with magnetic fields, will attract or repel based on the direction of the magnetic field for each wire. If the directions are the same, then the wires will attract to one another, but if they are in opposite directions they will repel from one another.

29. Describe whether two parallel wires will be attracted or repelled.

a) the currents flow in opposite directions.
 * They will repel because the resulting magnetic fields are going into one another, pushing them apart.

b) the currents flow in the same direction in both wires.

30. Describe the magnitude and direction of the magnetic field of at the center in a circular conducting loop. 31. What is a solenoid? How is it similar to the circular conducting loop? 32. Why does the solenoid have many important applications? 33. How is the magnitude and direction of the magnetic field of a solenoid determined?
 * They will attract to one another because the magnetic fields will go opposite one another, attracting them to one another.
 * The direction of the magnetic field in a loop can be found using the same second right hand rule, where the thumb points in the direction of current flow and the fingers are the direction of the magnetic field. The magnitude of the magnetic field can be calculated using the equation B=(µ o *//I//)/(2π*r). The magnetic field has a direct relationship with current and indirect relationship with the radius.
 * A solenoid is a series of circular conducting loops from one long conductor. It has the same method of finding the direction of the magnetic field as a circular loop, and it follows the same equation to find the magnitude of magnetic field. The only difference is that the magnitude of the strength of the magnetic field is multiplied by the number of loops, making it stronger. The resulting equation is B=n*(µ o *//I//)/(2π*r) where n = number of loops.
 * The solenoid makes it possible to increase the magnitude of the magnetic field on a long conductor. This can be used to increase the magnetic force exerted in that magnetic field, making it more efficient in tools such as a motor or conductor. This is because F B =q*v*B*sinø on a charge, so as the magnetic field strength increases, the magnetic force increases, producing more magnetic force on a charge.
 * The direction of the magnetic field of a solenoid is the same as with a circular conducting loop. The magnitude of the magnetic field, however, is greater than the magnetic field in a circular conducting loop because the magnetic field strength is multiplied by each number of loops in the conductor.

18. Complete Ch21 ConceptQ#11 & Problems #36,37,43 //in HW Journal//. (due 11/30)

19. Make a motor... In class 11/29 and post the video and discussion questions on your individual wiki. due 11/30 **__Its at the bottom__**

20.
Complete Ch21 Problems #65,67,82 //in HW Journal//. __ [|(][|due 11/30)] __ 21. Complete Ch21 Problems #46,47,53,72 in HW Journal. (due 12/1)

22. Do AP Problem #9. [| (due 12/2)]

23. Complete Prelab questions for Magnetic Force Lab on your individual wiki .(due 12/1) **__Its at the bottom__**

24. Do LAB: Magnetic Force ([|LabSheet]), with Lab Analysis and Group Report. ( In class 12/1, due 12/2)

25.
Complete Ch21 Concept Questions #15,16 & Problems #48,60,84 //in HW Journal//. // In class 12/1 // 26. Ch21 Problem #76, Concepts/Calc #80, //in HW Journal//. (due 12/5) 27. Do AP Practice Problems #7,11,&13. (due 12/5)

Activity: Making A Model Motor
__Objective:__ Using only the materials necessary, create a functioning motor that works using magnetic force.

__Hypothesis:__ By placing a magnet on top of a D-cell battery and creating a circuit where a magnetic coil is hanging above the magnet, the coil will use the current to create magnetic force, making the coil spin in mechanical force.

__Materials:__
 * 1 D-cell battery
 * 2 paper clips
 * 1 metal coil surrounded by plastic
 * 1 magnet
 * sand paper
 * tape

__Procedure:__ Begin by taking about a meter of the metal coil and wrapping it many times around the battery, until there is only a small amount of coil left. Remove the circle of coil from the battery, keeping it in its circular shape. Take the two ends of the coil and wrap them around the circle of coil, forcing it to keep its shape. Have the two ends of coil sticking out from the circle, with about 7 cm of coil on each side sticking out on opposite ends of the circle. Then place the battery on the desk (preferably in a battery pack) and place the magnet on top of the battery so that it is balanced on top. Then take the two paper clips and unwind them into one long strand of metal. Use tape to attach the paper clips to each end of the battery, letting the extra sticking out over the top of the battery. Bend the paper clips to form two 'hooks' that the coil can hang on. Before putting the coil on the paper clip hooks, use sand paper to expose the metal on the 7 cm of coil sticking out on each side of the circle. NOTE: YOU MUST SAND ONE END ON ALL SIDES, BUT ONLY ONE SIDE OF THE OTHER END. OTHERWISE, THIS WILL NOT WORK! Sand the coil so that the coil is exposed, then carefully place the coil in the metal hooks so that the circle hangs over the magnet. It may require a gentle push, but the coil will start spinning!

__Data:__ media type="file" key="Movie on 2011-11-29 at 15.15.mov" width="300" height="300"

__Discussion Questions:__ 1. How does a galvanometer work?
 * A galvanometer is an ammeter that uses current and magnetic force to get its readings. When a current is passed through a coil in a magnetic field, the coil experiences a torque force that is proportional to the current. In a galvanometer, the metal coil around the needle experiences this force, and it moves based on the magnetic force pushing it, which lets us determine the current going through it. The resistance that causes the needle to be at 0 when there is no current is created by a spring, creating some resistance for the movement of the needle.

2. Define motor and generator.
 * A motor is any device that takes electric force and manipulates it into mechanical energy. This can be done in many ways using magnetic force. A metal coil is placed next to a magnet and when current runs through the coil it creates a magnetic force, causing the coil to move or spin.
 * A generator is the opposite of a motor. It takes magnetic energy and converts it into electric energy in a process opposite to a motor. In many cases, a motor can be used as a generator if mechanical energy forces it to move the coil.

3. A motor is a device which converts electrical energy into mechanical energy (motion). Explain how your motor does so.
 * A metal coil is placed next to a magnet and when current runs through the coil it creates a magnetic force, causing the coil to move or spin. The movement of the coil is the mechanical energy and can be used in many different ways.

4. Why does the one rotor support have only ½ of its insulation sanded off?
 * It is important that when the coil is spinning, it is only receiving magnetic force in one direction. Because of this, it is important that the current in the coil only flows in one direction. As a result, the current can only be connected when the coil is facing one direction, and not the other way. By only sanding only 1/2 of one end of the coil, we only allow the circuit to be completed when the half that was sanded touches the metal. The circuit is only connected 1/2 the time as a result, but the current also only flows in one direction, causing magnetic force to only be in one direction.

5. How could the motor you built in be converted to a generator? Describe carefully what would have to be changed and what the result would be.
 * In order to convert our motor into a generator we would have to reverse the process, meaning the coil would have to be spun by mechanical force, creating an electric circuit and a magnetic force in the magnet and generating electrical energy that can flow in the circuit. As a result, we must remove the charged battery from our motor and replace it with something that can store charge, or even a rechargeable, charge less battery.

__Conclusion:__ Through this experiment we gained an improved understanding of motors, generators, electric energy, and magnetic force by creating our own motor. In creating the motor, we proved that the circuit in this hypothesis is fully functional, as the coil was spun by the magnetic force generated by the current. We have a better understanding of how magnetic force impacts an object, and finally an example of magnetic force that we can see! All of our other examples were theoretical and were not visible, but by seeing first hand how magnetic force converts electrical current into mechanical energy we are finally able to see the magnetic force, as well as how motors work. This lab could have been simpler if there were more proper supplies available. It was extremely frustrating trying to keep the paper clips attached to the ends of the battery, and the tape would not hold. If there was a clip designed to connect paper clips (or any metal rod) to the end of the battery, this process would have been much simpler. With the paper clips falling over I had trouble keeping the coil over the magnet, and it would not spin. Other than that the lab was a success and very informative way to learn about magnetic force.

=Lab: Magnetic Force on a Wire=

__Pre-lab Questions:__

1. The objective is stated as a question. What is your hypothesis? (Attempt to answer the question, to the best of your knowledge.)
 * Based on what we know about Magnetic force, I believe that magnetic force has a direct relationship with the magnetic field strength, current, wire length, and the angle the field and the current. There is also an indirect relationship between the Magnetic field strength, current, length, and angle; as one of these values decreases, the others increase(when possible).


 * Include the rationale for your hypothesis (Provide detailed reasoning here. This may take the form of a list of what you already know about the topics, with a summary at the end.)
 * My hypothesis is based on the equation F B =B*i*l*sin theta.(i=current; a capital i looks like a lowercase L) As any of these values, magnetic field strength, current, wire length, and angle, increases, the strength of the magnetic force increases and vice versa. You can also see an indirect relationship between the Magnetic field strength, current, length, and angle; as one of these values decreases, the others increase(when possible).


 * How do you think you might test this hypothesis? (What might you measure and how?)
 * By changing one controlled variable and keeping the others the same, I can measure how a change in each controlled variable, current, length, and angle, affect the other values from the equation above. By doing this with each controlled variable we can measure and graph the relationships between the values involved. We can vary the length of the wire and measure changes in the other variables (angle, current, and magnetic force) which can be measured. Magnetic force can be measured by placing the circuit and magnets on a balanced while disconnected, and measuring the difference in force on the balance once the circuit is connected due to the magnetic force(make sure the magnetic force is going up or down first in order to get a measurement from the balance).

2. Read the entire procedure through. ok

3. Design __data table(s)__ in order to record your observations __and__ calculations. Do this in Excel (preferable), and post a copy on your wiki.
 * Magnetic Force || Current || Length || Number of Magnets || Sin theta ||

4. Answer the following questions:
 * How is the direction of the magnetic force oriented with respect to the directions of magnetic field and current which produced it?
 * How do changes in the angle between the current and the magnetic field affect the force acting between them?
 * Changes in the angle between the current and the magnetic field will directly affect the magnetic force acting between them. As seen in the equation F B =B*i*l*sin theta the sine of the angle has a direct relationship to the magnetic force, and as the angle increases towards 90 degrees, the magnetic force increases.
 * Changes in the angle between the current and the magnetic field will directly affect the magnetic force acting between them. As seen in the equation F B =B*i*l*sin theta the sine of the angle has a direct relationship to the magnetic force, and as the angle increases towards 90 degrees, the magnetic force increases.


 * What angle between the current and the magnetic field produces the greatest force?
 * 90 degrees


 * What angle between the current and the magnetic field produces the least force?
 * 0 or 180 degrees


 * How is the magnitude of the force of magnetism related to the magnitude of the length of the wire carrying the current?
 * As the magnitude of length of the wire increases, the magnitude of the force of magnetism increases.

>>> y=B(.042)x >>> B(.042)=0.00559 >>> B=0.133T >>> >>> F B =(0.133)*(0.352)*(0.042) >>> F B =0.00197N
 * A graph of force vs. current has a trendline with an equation of y = 0.00559x. What is the theoretical magnetic field strength of the magnet used in this experiment if the loop is 4.2-cm long? Show your work.
 * F B =B*i*l*sin theta force=y current=x theta is ALWAYS THE SAME --> negligible
 * Find the magnetic force on the conducting loop described above, when the current is 0.352-A.
 * F B =B*i*l*sin theta