Ferrite magnets Nd-Fe-B magnets

1

• Ferrite magnets Nd-Fe-B magnets

1. Use the influence of magnets on iron filings
to investigate the magnetic fields of the
different magnets. Draw the magnetic fields
lines on the diagrams, and indicate where the
poles (strongest regions) of each of the magnets
are.
2. How do the shapes and spacings of the filings
depend on magnetic field strength and distance?
3. Evaluate the strength of each magnet
quantitatively by determining the longest chain
of paper clips that it can support. Write this
number on or by the picture of each magnet. Make
sure your chain extends in the direction of the
strongest field, as determined in question 1,
using a bent paper clip if necessary. Which
magnet(s) exhibit the strongest fields?
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4. Some currencies use magnetic ink. Are any
bills in your wallet attracted to these strong
magnets? If your answer is Yes, demonstrate
your answer to one of the TAs.
5. Do ferrofluids and iron filings arrange
themselves in a similar manner when brought near
a magnet?
6. What is the furthest distance you can hold
the Nd-Fe-B cube magnet from the compass and
reverse true N and S just by holding the magnet
in place and spinning it? Make sure you have the
magnet oriented in the direction of maximum
effect.
7. Suggest an explanation for the formation of
spikes (instead of a continuous particle
distribution like the filings) in ferrofluids.

• Consider the reaction for ferrofluid synthesis 2
  FeCl3 FeCl2 8 NH3 4H2O --gt Fe3O4 8 NH4Cl
• Is this a redox reaction? If so, identify the
  species being reduced and oxidized.
• What provides the driving force for this
  reaction to run?