[THE MAGNETIC FIELD - I]STUDIO Unit 11PHY-2054 College Physics IIWe have already introduced the concept ofthe magnetic field but we didn’t say muchabout it. In this unit, we do.In this unit we will find that the conceptsthat we learned for the ELECTRIC FIELDwork for the MAGNETIC field as well butthe force law is quite different.It should be possible to complete this unitin the two hour period. Please try!There will be some demonstrations duringthis unit and they will be best understood ifyou are at the right point in the activities.WARNING – In this unit the interaction of the metal tables might be a problem. In thelast unit we finally found a use for your textbook and this may work again. If not, try theexperiment on the floor. Sorry about that. Also, be sure to keep magnets and computersseparated as much as possible.Unit 11: MAGNETIC FIELDS(Modified by JBB from Lillian C. McDermott, Peter S. Shaffer and the Physics Education Group, Tutorialsin Introductory Physics (Homework), Prentice Hall, NJ, 1998)Objectives- to understand the nature of a magnetic field- to be able to represent a magnetic field at a point with a vector- to understand how to represent a magnetic field with field lines- to understand that a current gives rise to a magnetic field- to be able to determine the direction of the magnetic field due to a current-carrying wireFor Your Information: Permanent magnets have long been used in navigationalcompasses. As Figure 21.1 in the textbook illustrates, the compass needle is a permanentmagnet supported so it can rotate freely in a plane. When the compass is placed on ahorizontal surface, the needle rotates until one end points approximately to the north. Wesay approximately because some materials in the surroundings of the compass may affecthow the compass orients itself. The end of the needle that points north is labeled thenorth magnetic pole; the opposite end is the south magnetic pole. What kind of amagnetic pole is the north geographic pole? How do you know??2 | P a g e3 | P a g e1.0 Mini ExperimentEquipment: Small CompassesBar Magnet & Stand(a) Using the small compasses, determine what the North Magnetic Pole direction is andindicate it by drawing an arrow. Use more than one compass because some of the small(cheap!) compasses don’t always work properly. Compare your results with other tables.Be careful to keep away from other magnetic materials that may interfere with yourresults.(b) Set up the magnet and the stand on a flat (non-magnetic) surface (the table top maypossibly work for this!). Keep this magnet away from the compasses because it willattract it. Which way does the magnet point? Does it agreewith the compass (or close!) or not? Remember that othermagnetic materials can interfere with this part of theexperiment.____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ Using the other bar magnet in the box, determine the effect of each pole (marked) on eachof the other poles and fill in the table with “attract” or “repel”.Magnet 1 North Magnet 1 SouthMagnet 2 NorthMagnet 2 SouthDoes this remind you of anything you have seen before in this class?________________________________________________________________________________________________________________________________________________________________________________How close does Magnet 1 have to be to Magnet 2 for you to see an effect?________________________________________________________________________________________4 | P a g eEquipment:1 permanent magnet1 sheet of paperDEMO PORTION: 1 container of iron filingsA few small compasses10-12 stack magnets1.1 Place a bar magnet on a non magnetic surface as in the diagram below. The floor works as might a thick textbook. You can use the same bar magnet as above.a. Place a compass at each point shown on the diagram. Draw an arrow on the diagram indicating the direction that the north end of each compass points.b. DEMO – The effect of iron filings spread around a magnet followed by a briefdiscussion. http://www.youtube.com/watch?v=M9Gdm_OXKz4The motion of the compasses and the alignment of the iron filings give us the idea thatthere is a quantity with a magnitude and a direction at each point in space that determinesthe motion of the compasses. We will call this a magnetic field. We will rigorouslydefine a magnetic field later. We will define the direction that the north ends of eachcompass points as the direction of the magnetic field. Recall that we designatedthe electric field with the letter E and that it was a VECTOR. Similarly, we designate themagnetic field with the letter B. As with the electric field B is a VECTOR as well.THE STACK MAGNETS ARE VERY STRONG AND CAN CHANGE THEDIRECTION OF THE MAGNETIC FIELD IN THE COMPASS IF IT GETS TOOCLOSE. PLEASE BE CAREFUL WITH THIS EXPERIMENT. ALSO, BE CAREFULTHAT YOU DON’T HURT YOURSELF BY PUTTING YOUR FINGER BETWEENTHE POLES OF A MAGNET MADE WITH THIS MATERIAL. PLEASE OBSERVETHIS WARNING BECAUSE WE DO NOT HAVE ANY BAND-AIDS IN THECLASSROOM. 5 | P a g ec. On the diagram below draw a vector at each of the points that indicates the magnitudeof the magnetic field at that point. How did you determine this? If you draw the vectorsto scale, the arrows that you drew represent the magnitude and the direction of themagnetic field. This is similar to what you did with the Electric Field.(Use one of the bar magnet for this part of the work.)1.2 Obtain a stack of small magnets (referred to as “stack magnets” in these experiments) and place them as in the diagram below.6 | P a g ea. Draw the magnetic field vectors at each of the points. b. Remove the left half of the stack as in the diagram below.Draw the magnetic field vectors at each of the points in the diagram above.c. Replace the left half and remove the right half as in the diagram below.Draw the magnetic field vectors at each of the points in the diagram above.7 | P a g ed. Compare the field vectors for the two halves to that of the whole. Is your observationconsistent with the idea that magnetic fields obey