Summer Research Program for Science Teachers
Bronx High School of Science
How do compasses work?
Learning Objectives: Students will be able to:
1. Draw magnetic field lines for a magnet.
2. Describe the characteristics of magnetic field lines.
Place a “see through” compass on an overhead projector.
Place bar magnet next to the compass and follow the field lines with the compass.
Place a transparency over the magnet and pour iron filings over it to get the general pattern.
The Chinese (121 A.D.) found that a suspended iron rod that had been exposed to a natural magnet (lodestone or magnetite) would align itself in the north-south direction.
Why does this happen?
The Earth is magnetic.
Like poles repel [N + N or S + S] and unlike poles [N + S] attract.
How are the
lines similar to electric field lines?
How can you
tell that the magnetic field is strongest near the poles?
How can you
tell that the Earth’s magnetic north is really like the south pole of a bar
Flux lines never cross
Where will the compass point?
Where is the flux density greatest?
Where is the field greatest?
Why does the Flux density increases inside the soft iron?
Magnetic field lines always form closed loops.
Explain in terms of domain theory:
Ø How metals get magnetized through induction.
Ø How permanent magnets are formed.
Ø How hammering a nail will cause it to become magnetized.
This Lesson Plan aligns with following National Science Education Standards:
Standard A: Plan an inquiry–based science program.
Standard B: Guide and facilitate learning.
Standard C: Engage in ongoing assessment of teaching and student learning.
Standard D: Design and manage learning environments that provide students with the time, space, and resources needed for learning science.
Standard E: Develop communities of science learners that reflect the intellectual rigor of scientific inquiry and the attitudes and social values conducive to science learning.
Standard F: Participate in the ongoing planning and development of the school science program.
NYC Performance Standards:
S5 – Scientific Thinking
S7 – Scientific Communication
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