March 7, 2002

MFF 1a

This set has electric charges sitting at rest near the poles of permanent magnets. The issue being explored is that of treating magnetic poles as if they have electric charges. Students often think that magnetic poles are charged, they usually take north poles as positively charged, and that they can attract or repel static electric charges.

MFF 1b

This set has electric charges either sitting at rest on, or moving along, the axial line of a circular coil that is carrying a current. The question is how the current in the coil will affect the charge. This set is analogous to MFF1a except that the magnetic element is a current carrying coil rather than a permanent magnet.

MFF 2a

This set is one of the BASIC sets. It deals with charges moving in magnetic fields. There is some variation among the items in the actual physical arrangements, but all of the items in the set ask about the force on and/or motion of electric charges moving in magnetic fields.

MFF 3a

This is another BASIC set. This one deals with electric charges moving near straight current-carrying wires. The questions in the items in the set ask about the force on or acceleration of the particle.

MFF 4a

This is another BASIC set although one question is used throughout. This set deals with the force on a current carrying wire segment when placed in a magnetic field.

MFF 6a

This BASIC set focuses on the magnetic field associated with a long straight current carrying wire. Items ask about magnitude and/or direction of the field at specified points.

MFF 7a

This BASIC set is similar to the previous set except that it focuses on the magnetic field at the center of a circular current-carrying coil of wire. Again the questions in the items ask about magnitude and/or direction of the field.

MFF 8a

This set deals with the issue of what is called weak superposition. Weak superposition is the idea that the field at a point, or the force on a body, due to one source of magnetic field will be altered if there is another field (force) source in the region. This is different from the net field (force) being the sum of the fields (forces).

MFF 8b

This set deals with the superposition of magnetic fields due to three parallel long straight current-carrying wires.

MFF 8c

This set is also about superposition, but in these situations the fields are being added at the location of a third current-carrying. So the students have to decide whether they think a current-carrying wire produces a field at its own location.

MFF 10a

This set focuses on the issue of a magnetic field not doing work on a moving charge since the force and the velocity are always perpendicular to each other.

EMI 2a

The induced emf in a rectangular wire loop that is being moved into, through and/or out of a uniform magnetic field is the focus of this set.

EMI 3a

This set is a variation on the theme of the previous set since the physical situation is the same (a rectangular wire loop being moved into, through and/or out of a uniform magnetic field) but this time the question is about the current in the loop.

EMI 3b

This set has light bulbs in circular wire coils that are situated next to long straight current-carrying wires. The currents in the wires are changing and the students are to predict, or explain, the comparative brightness of the bulbs. One issue examined in the set is whether students recognize that it is the rate of change that affects brightness and not the actual current value.

EMI 3c

This set has a physical situation where a circular loop of wire is inside and concentric with a solenoid. The questions in the items focus on the current in the wire loop for changes, or lack of change, in the current in the solenoid.

EMI 5a

This set deals with a permanent magnet moving toward, or away, from a circular coil of wire that is suspended from a string. The issue explored is how the induced magnetic field interacts with the changing field from the moving magnet.