Conceptual Questions Chap. 19

1
Conceptual Questions Chap. 19

1. Can you use a compass to detect the currents in
   wires in the walls near light switches in your
   home?
2. Can a constant magnetic field set into motion an
   electron at rest? Why or why not?
3. Is it possible to orient a current loop in a
   uniform magnetic field such that the loop will
   not tend to rotate? Explain.
4. A magnet attracts a piece of iron. The iron can
   then attract another piece of iron. On the basis
   of domain alignment, explain what happens in each
   piece of iron.

No, for two reasons. First, there are wires
carrying currents in opposite directions, so the
net magnetic field is very small. Second, the
current direction is alternating at 60 Hz, so the
magnetic field is oscillating at 60 Hz also.
This frequency is too fast for the compass to
follow, so the effect on the compass reading
averages to zero.
No, since a charge at rest is completely
unaffected by a magnetic field.
Yes, if the magnetic field is directed
perpendicular to the plane of the loop, the
forces on opposite sides of the loop will be
equal in magnitude and opposite in direction in
the plane of the loop, which will not cause a net
torque on the loop.
The magnet causes domain alignment in the iron
such that the iron becomes magnetic and is
attracted to the original magnet. Now that the
iron is magnetic, it can produce an identical
effect in another piece of iron.