ism_chapter_27

# ism_chapter_27 - Chapter 27 Sources of the Magnetic Field...

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519 Chapter 27 Sources of the Magnetic Field Conceptual Problems *1 Picture the Problem The electric forces are described by Coulomb’s law and the laws of attraction and repulsion of charges and are independent of the fact the charges are moving. The magnetic interaction is, on the other hand, dependent on the motion of the charges. Each moving charge constitutes a current that creates a magnet field at the location of the other charge. ( a ) The electric forces are repulsive; the magnetic forces are attractive (the two charges moving in the same direction act like two currents in the same direction). ( b ) The electric forces are again repulsive; the magnetic forces are also repulsive. 2 No. The magnitude of the field depends on the location within the loop. 3 Picture the Problem The field lines for the electric dipole are shown in the sketch to the left and the field lines for the magnetic dipole are shown in the sketch to the right. Note that, while the far fields (the fields far from the dipoles) are the same, the near fields (the fields between the two charges and inside the current loop/magnetic dipole) are not, and that, in the region between the two charges, the electric field is in the opposite direction to that of the magnetic field at the center of the magnetic dipole. It is especially important to note that while the electric field lines begin and terminate on electric charges, the magnetic field lines are continuous, i.e., they form closed loops. 4 Determine the Concept Applying the right-hand rule to the wire to the left we see that the magnetic field due to its current is out of the page at the midpoint. Applying the right- hand rule to the wire to the right we see that the magnetic field due to its current is out of

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Chapter 27 520 the page at the midpoint. Hence, the sum of the magnetic fields is out of the page as well. correct. is ) ( c 5 Determine the Concept While we could express the force wire 1 exerts on wire 2 and compare it to the force wire 2 exerts on wire 1 to show that they are the same, it is simpler to recognize that these are action and reaction forces. correct. is ) ( a *6 Determine the Concept Applying the right-hand rule to the wire to the left we see that the magnetic field due to the current points to west at all points north of the wire. correct. is ) ( c 7 Determine the Concept At points to the west of the vertical wire, the magnetic field due to its current exerts a downward force on the horizontal wire and at points to the east it exerts an upward force on the horizontal wire. Hence, the net magnetic force is zero and correct. is ) ( e 8 Picture the Problem The field-line sketch follows. An assumed direction for the current in the coils is shown in the diagram. Note that the field is stronger in the region between the coaxial coils and that the field lines have neither beginning nor ending points as do electric-field lines. Because there are an uncountable infinity of lines, only a representative few have been shown.
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## This homework help was uploaded on 02/26/2008 for the course PHYSICS 11 taught by Professor Licini during the Spring '07 term at Lehigh University .

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ism_chapter_27 - Chapter 27 Sources of the Magnetic Field...

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