Subject Matter Research- MagnetsGrey CohortAndrea BalarezoKristin KirkpatrickLindsi CiuffetelliMaroon CohortKatherine RountreeMelissa KrollKevin Swartz

Big Ideas

Permanent magnets

Permanent magnets are those that retain a certain level of magnetism once

they are magnetized. They are generally made of ferromagnetic material, which

consists of atoms and molecules that each have a magnetic field and are positioned

to reinforce each other (Jezek, 2006). Permanent magnets are the kind that we are

most familiar with, like the kind that people use to hang items on their refrigerators.

There are four different types of permanent magnets based on their

composition and each type varies in how easily they can be demagnetized, how

strong they are, and how their strength changes due to temperature. Rare earth

magnets, Neodymium Iron Boron and Samarium Cobalt, are very strong and very

difficult to demagnatize. Alnico is a type of permanent magnet that is made of

Aluminum, Nickel, and Cobalt and is easily demagnetized, but least affected by

temperature. The current most popular type of permanent magnets is Ceramic or

Ferrite, made of Strontium-Iron, which is the weakest type of magnet, and its

magnetic strength varies with temperature (What are permanent magnets made of?,

2000).

Permanent magnets can be demagnetized by high heat, contact with another

magnet, or hammering, which loosens the magnet’s atoms (Jezek, 2006).

Induced Magnets

Induced magnets, or temporary magnets, are ones that only exhibit magnetic

properties when they are inside another magnetic field (“How magnets work,”

2006). One may easily observe an induced magnet after attaching a regular paper

clip to a permanent magnet. If you make a chain by touching this paper clip to

another, it will “magically” lift it up. This is because the first paper clip is an induced

magnet; when you remove it from the permanent magnet, it no longer acts this way.

People may also make an induced magnet by repeatedly stroking a magnetic

object, from tip to tip, along one part of the magnet. This will force the molecules in

the object to temporarily align themselves with the poles, thus creating an induced

magnet.

Electromagnets are another example of induced, or temporary, magnets.

These are created by winding copper wire into tight coils around a piece of soft iron

and passing an electrical current through it. When the current is flowing through

the wire, the iron is magnetized, creating an electromagnet. When the current stops

flowing, the iron is no longer magnetized (“How magnets work,” 2006).

Electromagnets are used in most electrical household items, including washing

machines, computers, and stereo systems.

Magnetic Force

A magnet is an object that has a magnetic field surrounding it. Every magnet

will have at least two poles—a North pole and a South pole. If a magnet is cut in

half, it will continue to have two poles. It has not been proven possible to have a

magnet without two poles, so no matter how small a magnet gets, it will still have

both. Typically, magnetic field lines are considered to leave from the North pole and

enter through the South Pole (Hoadley, 1998). The magnetic field that surrounds

every magnet is created by the lines of force going between the North and South

poles (Flaherty, 1999). Magnets attract ferrous objects like pieces of iron, steel,

nickel, and cobalt. Magnets do not attract all metals, as is the common

misconception. A magnet’s pole will also attract another magnet’s unlike pole. For

example, the North pole of one magnet will attract the South pole of another. On the

other hand, repulsion will occur when two like poles of magnets are put close

together (Jezek, 2006).

Magnet Experiments

1) Magnetic Force- attraction and repulsion of poles

This experiment, found in Magnetism by Penny Norman, is designed for

students to discover how magnets attract and repel other magnets based on poles

(2008, p.8). Students would be given a pencil or straw, and five circular magnets

that have red painted on its north pole and white painted on its south pole. They

would then be told to put the straw between the hole of one of the magnets, with the

red side facing towards the ceiling. Placing one magnet down the straw with the

white side facing up, watch how the second magnet seems to “float” on the straw.

The students would be allowed to explore how to make other magnets float or stick

to each other, and asked to explain why they think this happens. This is a fun way

for students to discover the polarity of magnets and the force within them.

Here is an example of the experiment in motion:

2) What is magnetic?

Through a “discovery bottle,” detailed in Discovery Bottle by Kay Kent,

students are able to see what a magnet sticks to and what it does not (2002, p.17).

We would put various magnetic objects (such as paper clips, scissors, a brass clasp)

and non-magnetic objects (such as a plastic badge, a penny, aluminum foil) into an

empty two-liter bottle. The bottle would then be filled with paper shreds so the

objects are hidden from students view. Using a magnet rod, students would run it

up and down the outside of the bottle to discover what items stick to the magnet

through the bottle. They would then use sheets to draw which objects they saw

before the bottles were emptied.

We did not have a plastic bottle, so we put the items onto a table and went “fishing;”

however, here is how it would look in the bottle, shown on the worksheet:

3) Does the size of the magnet determine its strength?

The book, More Picture-Perfect Science Lessons, by Ansberry and Morgan

describes an experiment for students to discover the strength of a magnet (2007,

p.127). This experiment requires magnets of several different sizes and shapes. We

put twenty paper clips into a paper bag, and tied a string to two different shapes of

magnets, circular and bar shaped. We then “went fishing” into the bag to see how

many paper clips each magnet would pick up. Students could then make a graph of

how many each type of magnet picked up for a visual representation of the different

strengths of magnets.

Here is the experiment in motion:

Scientific MisconceptionsA scientific misconception is an idea or belief that a student has about science that

is inconsistent with the actual scientific idea. Often times, the student doesn’t even know

that they hold these misconceptions and struggle with releasing them. Misconceptions are

formed a number of ways, which include incorrect information from the parents, by word

of mouth, and by the students trying to make sense of an idea with limited experience or

understanding. Misconceptions about science are very common; however, they can be

used to help the students build on their own understanding.

Common misconceptions students hold about magnets and magnetism

A misconception about magnets is that magnets only attract and do not repel.

Several of the students might think that magnets will be attracted to everything, including all metals.

Some students think that magnets are only attracted to iron and that all magnets are made of iron.

It is thought by some that magnets are only attracted to metal objects that are silver.

Students have a hard time with the concept that magnetic fields are not two-dimensional like what they see in their textbook. In fact, magnetic fields are three-dimensional and surround the object.

Students think that only metal magnets have a magnetic field.

It is common for students to think that the larger the magnet the stronger the magnet pull is.

Some students believe that magnetism is magic.

Many students think that magnetism cannot go through objects and that things that are insulators could block magnetism.

A very common misconception about magnetism, even with adults, is that the geographic and the magnetic poles of the earth are in the same place.

Students commonly refer to the poles of a compass as north and south and believe that the north pole of the compass points to the north pole of the earth, when in fact the south pole of the magnets points north due to its attraction.

Diigo Links Posted by Lindsi Ciuffetelli

Bibliography

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