A bar magnet is cut in half as shown

1- Below is an image of a bar magnet, with its Poles indicated. Imagine a compass were placed at position X and then at position Y. Which direction would the North Pole of the compass point at each position?

Select one:

a.

The North Pole of the compass would point to the right at position X and to the right at position Y.

b.

The North Pole of the compass would point to the right at position X and to the left at position Y.

c.

The North Pole of the compass would point to the left at position X and to the left at position Y.

d.

The North Pole of the compass would point to the left at position X and to the right at position Y.

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2- Below are images of three positions of a compass near a bar magnet. The pointed end of the compass needle represents its North Pole. Only one of these three images shows the correct orientation of the compass needle, the other two are incorrect. Which image is correct?

Select one:

a. Image A

b. Image C

c. Image B

----------------------------------------------------------------3-Which of the following statements best explains why the North Pole of a compass needle points (approximately) toward the geographic North Pole of the Earth?

Select one:

a.

The South Pole of the imaginary large bar magnet inside the Earth lies close to the geographic North Pole.

b.

The North Pole of the imaginary large bar magnet inside the Earth lies close to the geographic North Pole.

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4- which of the following materials can interact with (be affected by) a magnet?

Select one:

a. All of them

b. Aluminum

c. Brass

d. Steel

e. Copper

5- Consider the model from a different group, similar to but not the same as Group 2’s model:

Description: There are no magnetic entities associated with the unmagnetized nail, but when a magnet is rubbed along the surface of the nail, it deposits small N and S entities (like dust particles) loosely along the surface, as shown.

Which of the following observations made by some other groups would be difficult to explain (or could not be explained) using this model? (Choose all that apply.)

Select one or more:

a.

Cutting the nail anywhere along its length produces two pieces that each behave like two-ended magnets.

b.

The magnetized nail behaves like a two-ended (bar) magnet.

c.

When cut in half, each end of each half of the nail (four ends in all) can pick up the same number of paper clips.

d.

Cutting the magnetized nail in half produces two pieces that each behave like two-ended magnets.

e.

After dropping the magnetized nail in water and removing it, the wet nail is still magnetized.

f.

Each end of the magnetized nail can pick up the same number of paper clips.

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6- Now consider a group who found that, when they cut a magnetized nail into either halves or ¼ and ¾ pieces, the pieces of the magnetized nail still behaved as if they were two-ended.

Description: Inside the nail, there are equal numbers of separate N and S magnetic particles that can move around when attracted or repelled by a magnet. In the unmagnetized nail, they are all jumbled up randomly. When the nail is rubbed with one pole of a bar magnet, the magnetic particles arrange themselves as shown in the diagram.

Which of the following observations made by some other groups would be difficult to explain using this model? (Choose all that apply.)

Select one or more:

a.

After dropping the magnetized nail in water and removing it, the wet nail is still magnetized.

b.

The magnetized nail behaves like a two-ended (bar) magnet.

c.

Each end of the magnetized nail can pick up the same number of paper clips.

d.

When cut in half, each end of each half of the nail (four ends in all) can pick up the same number of paper clips.

e.

Cutting the nail anywhere along its length produces two pieces that each behave like two-ended magnets.

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7- This group’s model is similar to the last group’s model. In this case, the group performed experiments in which they cut a number of magnetized nails into two pieces of various lengths and found that both pieces were always two-ended. Here is their model for the magnetized nail:

Description: Inside the nail there are equal numbers of separate N and S magnetic particles that can move around when attracted or repelled by a magnet. In the unmagnetized nail, these N and S particles are all jumbled up randomly. When the nail is rubbed with one pole of a bar magnet, the magnetic particles arrange themselves alternately along the length of the nail.

Could this model be used to explain the observation that when a magnetized nail is cut into two pieces of arbitrary lengths both pieces are always two-ended?

Select one:

a.

Yes, according to the model diagram, anywhere the nail is cut would produce two pieces that are both two-ended.

b.

No, according to the diagram, there are some places where the nail could be cut and the two pieces produced would not be two-ended.

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8- Here are four possible things that could be done to any object.

I.Hit it with another hard object.

II.Heat it to a very high temperature.

III.Cool it to a very low temperature.

IV.Bring it close to one end of a permanent magnet.

Considering all the evidence you have seen in this unit, in terms of the alignment of domains model, which of these seem to be able to change the orientation of at least some of the domains in a ferromagnetic object?

Select one:

a. I, II, III, and IV

b. II and III

c. I, II, and III

d. I and II

e. I, II, and IV

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9- A group of students constructed the following explanation for why the N-pole of compass needle rotated toward the tip of a magnetized nail placed at the E-label, but after the nail was heated the needle showed no reaction.

(1) Before it is heated all the S-poles of the domains in the magnetized nail are facing the tip of the nail, making it a S-pole that attracts the N-pole of the compass needle. (2) When the nail is heated the domains get jumbled up with no preferred direction of alignment. This means the tip of the nail is now unmagnetized and the tip is longer any particular pole. (3) Since there is an attraction between an unmagnetized object and both poles of a magnet, both ends of the compass needle are now attracted to the nail. These two attractions tend to make the needle rotate in opposite directions, so they cancel each other out and the needle does not move.

What is your evaluation of this explanation in terms of whether it is well constructed or not?

Select one:

a.

It is well-constructed.

b.

It is not well constructed because it is not relevant.

c.

It is not well constructed because the diagram is not clear or the narrative is not easy to read.

d.

It is not well-constructed because the diagram and narrative are inconsistent.

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10- Now consider only the narrative from the same explanation

(1) Before it is heated all the S-poles of the domains in the magnetized nail are facing the tip of the nail, making it a S-pole that attracts the N-pole of the compass needle. (2) When the nail is heated the domains get jumbled up with no preferred direction of alignment. This means the tip of the nail is now unmagnetized and the tip is longer any particular pole. (3) Since there is an attraction between an unmagnetized object and both poles of a magnet, both ends of the compass needle are now attracted to the nail. These two attractions tend to make the needle rotate in opposite directions, so they cancel each other out and the needle does not move.

What is your evaluation of this narrative in terms of whether it is accurate or not?

Select one:

a. It is accurate.

b.

It is not accurate because part (2) is not consistent with the class consensus model.

c.

It is not accurate because part (3) is not consistent with how we know unmagnetized and magnetized objects interact with each other.

d.

It is not accurate because part (1) is not consistent with the class consensus model and/or the Law of Magnetic Poles.

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11- Again, consider only the narrative from the same explanation

(1) Before it is heated all the S-poles of the domains in the magnetized nail are facing the tip of the nail, making it a S-pole that attracts the N-pole of the compass needle. (2) When the nail is heated the domains get jumbled up with no preferred direction of alignment. This means the tip of the nail is now unmagnetized and the tip is longer any particular pole. (3) Since there is an attraction between an unmagnetized object and both poles of a magnet, both ends of the compass needle are now attracted to the nail. These two attractions tend to make the needle rotate in opposite directions, so they cancel each other out and the needle does not move.

What is your evaluation of this narrative in terms of whether it is well-reasoned or not?

Select one:

a.

It is not well reasoned because it does not explain why the compass needle is attracted to the nail before heating.

b.

It is not well-reasoned because it does not explain why the compass needle does not react to the the nail after it was heated.

c.

It is not well-reasoned because it does not explain why heating the nail causes the domains to change their orientation.

d.

It is well-reasoned.