[PDF] Magnetism

86789_3P223Magnetism.pdf

Magnetism

Investigation

Manual

PHYSICS

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MAGNETISM

Overview

Students will investigate the relationship between electricity and magnetism by building several electromagnetic devices. Students will construct an electromagnet, electric motor, and electric magnetic induction.

Outcomes

࠮Investigate the properties of magnets. ࠮Analyze the relationship between electricity and magnetism. ࠮ Apply the principle of induction to simple electromagnetic devices (solenoid, motor, and speaker).

Time Requirements

Preparation

.......................................................................5 minutes Activity 1: Properties of Electric Currents.......................20 minutes

Activity 2: Solenoid

.........................................................20 minutes Activity 3: Coiled Wire Electromagnet ............................20 minutes Activity 4: DC Electric Motor ..........................................20 minutes Activity 5: Electric Speaker .............................................20 minutes 2 Carolina Distance Learning

Table of Contents

2 Overview

2 Outcomes

2 Time Requirements

3 Background

8 Materials

9 Safety

9 Preparation

10 Activity 1

11 Activity 2

11 Activity 3

13 Activity 4

14 Activity 5

15 Disposal and Cleanup

Background

The discovery of magnetism dates back to circa

589 BCE, when Thales of Miletus found that

certain stones were able to attract pieces of iron.

These stones, sometimes called lodestones,

became known as magnetite, possibly named for the Greece region Magnesia. It was discov- ered that all magnets exerted a force on objects containing iron and that all magnets had two poles, where like poles repelled each other and unlike poles attracted each other. A is a region of space around a magnet where magnetism is exerted. In perma- with the alignment of atoms. All magnets have a detected and measured by the presence of lines of force that extend from the north pole of the magnet to its south pole, as shown in Figure 1. Figure 1.The properties of a magnet are attributed to the orientation of its magnetic domains , which are nonmagnetic piece of metal, the domains are organized randomly, as shown in Figure 2; the Ɉ each other out. In a magnet or a piece of metal that has been temporarily magnetized, the Ɉ add up, increasing the strength of the overall be made into a temporary magnet by repeatedly rubbing it against a permanent magnet. Doing so aligns its magnetic domains, and the iron will subsequently acquire the properties of a magnet. However, the strength of the magnet is Ɉ

Figure 2.

Figure 3.

continued on next page www.carolina.com/distancelearning 3

MAGNETISM

Background

continued

Magnetic lines of force are concentrated at the

poles. If two like poles (north/north or south/ south) of two magnets are in close proximity to each other, the magnetic force of the magnets causes them to repel each other. If two opposite poles (north/south) are in close proximity to each other, the magnetic force of the magnets creates an attractive force between the two poles.

Earth itself is a magnet. The rotation of the

molten iron outer core causes charged ions to surface from deadly solar radiation. Magnetic for navigation.

Around the 6th century BCE, the ancient Greeks

Ɉ they rubbed pieces of amber with wool, which were subsequently able to pick up pieces of straw. In the 18th century, scientists such as Benjamin Franklin continued to study electricity.

However, it remained a novelty with little prac-

tical purpose until the early 19th century. At that time, Hans Christian Ørsted, a Danish physicist, noted that when a current passed through a demonstration of the relationship between elec- tricity and magnetism.

In 1821, Michael Faraday, an English scientist,

when a magnet moves near a coil of wire, a current is generated in the wire - a phenom- enon called induction . This phenomenon also works in reverse: when a current passes through

permanent magnet or electromagnet. Induc-tion is the working principle behind electric motors and Faraday developed the concept of a basic working motor. More practical working motors were later developed, and when power distri-bution systems became available later in the 19th century, electric motors found commercial success in many applications.

Electromagnets

As described by Ørsted, if a magnetic compass

is brought close to a current-carrying wire, the wire. If the wire is wound in a coil, the magnetic loops, creating a stronger magnet. A solenoid , a cylindrical coil of wire, takes advantage of this principle. Placing an iron core in the solenoid

This concept is the basic principle of an

electromagnet .

Electromagnets made of coils of wire carrying

currents are used in many modern devices. For example, a solenoid in a car engine is used to is generated moves a plunger inside the coils, allowing it to make contact with the starter elec- trical terminals. An electric motor converts elec- trical energy to mechanical energy by allowing a coil of wire to turn rapidly when current is in the coil interacts with that of a permanent magnet or another stationary coil near the spin- ning coil to produce linear or rotary force. An continued on next page 4 Carolina Distance Learning electric generator functions according to the same principles in the opposite manner; in this application, a mechanical force such as a hand crank or an internal combustion engine turns the spinning coil, inducing an electrical current in the coil. Finally, in a speaker connected to a device, such as a radio, the current in the coil varies according to the signal from the radio. As - nent magnet in the speaker pushes and pulls on a coil attached to a diaphragm, a material with a large surface area. The diaphragm vibrates with the movement of the coil, transferring energy to molecules in the air to create sound waves.

Magnetic Fields

Ɉ are often explained by the previously discussed understanding how electric charges and magnets can apply a force at a distance. An Ɉ mathematically or measured experimentally. . ;OLTHNUL[PJMVYJLL_LY[LK\WVUHJOHYNLK

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amount of charge in the particle. ࠮

;OLTHNUL[PJMVYJLL_LY[LK\WVUHJOHYNLKWHY[PJSLPUHTHNUL[PJÄLSKKLWLUKZVU[OLspeed and direction of the charged particle.

࠮

0MHJOHYNLKWHY[PJSLTV]LZHSVUNH[YHQLJ-magnetic force exerted upon the particle is zero.࠮;OLTHNUL[PJMVYJLL_LY[LK\WVUHWVZP[P]LS`charged particle is opposite in direction from the magnetic force exerted upon a negatively charged particle.

࠮

0MHJOHYNLKWHY[PJSLTV]LZH[HUNSL[OL[H¿YLSH[P]L[V[OLKPYLJ[PVUVM[OLTHNUL[PJÄLSKthe magnetic force exerted on the charged ʿ

Electric Field vs. Magnetic Field

Ɉ . (ULSLJ[YPJÄLSKL_LY[ZHMVYJLVUHJOHYNLK WHY[PJSLPM[OLWHY[PJSLPZSVJH[LKPU[OLÄLSK

I\[HTHNUL[PJÄLSKVUS`L_LY[ZHMVYJLVUH

charged particle that is moving.

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Consider Figure 4. If a wire is placed in a

the wire, there is a force on the wire that causes it to move. This observation is a demonstration of the principle underlying telegraphs, electric motors, and electric generators. The direction in which the wire moves depends on the direc- tion of the current relative to the direction of between the north and south poles of a horse- shoe magnet. The direction of the current is perpendicular to the direction of the magnetic continued on next page www.carolina.com/distancelearning 5

MAGNETISM

Background

continued

Figure 4.

Until the circuit is closed, the magnet has no

Ɉ of charged particles, the motion of the charged particles is random and in all directions. When - lished in the wire, causing the electrons in the wire to move in one direction. If the direction of that movement is at an angle relative to the as a result of the magnetic force. If the direc- tion of the current is perpendicular to that of the will be maximized.

To determine the direction in which the wire

will move, you can apply the right-hand rule . as shown in Figure 5. Find the location where current (from the positive terminal to the nega- tive terminal). Point the palm of your hand in the pole to the negative pole). In this position, your thumb is pointing toward the direction of the force on the wire. Figure 5. (indicated by the letter B ) is down. The direction of the current ( I ) is from the wire shown on the right to the wire on the left, and the direction of the force ( F ) on the wire is away from the horseshoe magnet.

Figure 6.

continued on next page 6 Carolina Distance Learning F BI I B F

Another right-hand rule indicates the direction

Point your thumb in the direction of positive

around the wire. At any point on that circle, the Ɉ a wire is wound in a coil, each loop in the coil coil acts as a short bar magnet with a north and south pole. In an electric motor, the poles of the coil are attracted or repelled by the magnetic depending on its orientation.

Figure 7.Magnetism Every Day

Magnetism and induction play vital roles in

everyday lives: magnetic door openers, sensors ɉ motors, transformers, generators, and cell phone chargers are just a few examples. Two ɉ and cell phone chargers. ࠮ ;YHIJSPNO[ZVWLYH[LLP[OLYVU[PTLYZVYVU sensors. In urban areas, there often is enough

ɉɉ

timers. However, in more rural or suburban ɉ sensors employ technology to determine when vehicles are at an intersection. An inductive loop is embedded under the ground. Inductive loops are coils of wire that detect changes in are placed below the concrete, they produce vehicle, made primarily of metal, passes over the loop, it acts as a metal core for the loop and changes the current in the coil below the ɉ light to cause it to change. ࠮

0M`V\\ZLH^PYLSLZZJOHYNLY[VJOHYNL`V\Ycell phone, you are using the inductive power of magnetism. In fact, this wireless transfer technology is called Inductive Power Transfer (IPT). To put it simply, the wireless charger contains coils of wire. When you place a cell phone on top of the charger, electrical current

www.carolina.com/distancelearning 7

MAGNETISM

Materials

Included in the conceptual physics electricity module kit: 8 Carolina Distance Learning

Magnetic

compassSet of ring magnetsMagnet wire

Foam cup

Nail2 Alligator clip leads

Box of

paper clips

StrawPie plate

4 D-cell

battery holdersAudio jack

Sandpaper

Reorder Information:

Replacement supplies for the Magnetism investigation (Conceptual Physics

Electricity Module kit, item number 580410)

can be ordered from Carolina Biological Supply

Company.

Call:

800.334.5551 to order.

Needed but not supplied:

࠮Masking tape ࠮Salt ࠮Permanent marker ࠮ Music device with an audio jack connection port, such as a smartphone or computer

4 D-cell

batteries

Safety

For Activity 4 only:

1. Using the magnet wire, create a coil

with at least 30 turns with a diameter of approximately 2 cm (about the diameter of a

C-cell battery). Leave about 8 cm of w

ire on each end of the coil. This coil will be used in the motor in Activity 4.

2. Unwind 2 paper clips to make brushes for the

motor to be used in Activity 4. Form the clips to provide a place for the straight ends of a wire coil to rest (see Figure 8).

Figure 8.

For Activity 5 only:

1. Create a coil using the magnet wire. Wrap

the wire around the D-cell battery at least 30 times, leaving approximately 4 cm of wire at the end of the coil. This coil will be used in the speaker in Activity 5.

2. Secure the loose ends by wrapping a few turns around the coil at opposite ends. Use the sandpaper to strip the ends of the wire, removing the enamel on all sides.

www.carolina.com/distancelearning 9

Safety goggles should be worn

during this investigation. There are no additional safety concerns. Read all instructions for these activities before beginning. Follow the instructions closely, and observe established laboratory safety practices.

The components included in this kit use low

voltages and low currents and are safe to handle. Do not use other components as substitutes for those included in this kit.

Keeping circuits connected for extended

periods of time can cause wires or compo- nents to overheat or batteries to leak. Keep circuits connected for only as long as required to complete analysis; afterward, disconnect the alligator clips from the batteries.

Do not eat, drink, or chew gum while performing

this activity. Wash your hands with soap and water before and after performing the activity.

Preparation

1. Read through the activities.

2. Obtain all materials.

3. Clean the work area.

4. View the following video:

Stripping a Magnet Wire

https://link.brightcove.com/services/ player/bcpid2632427758001?bck- ey=AQ~~,AAAABCtdqqE~,SlJki-

0kLsZX53Gsu9yDKELFtHI3Ejt7R&b

ctid=4573412165001

ACTIVITY

ACTIVITY 1

A Properties of Electric Currents

1. Collect a D-cell battery, a D-cell battery

holder, an alligator clip lead, and the magnetic compass.

2. Place the compass on a level surface away

from metallic objects.

3. Move the compass across the level surface

while constantly turning it. Observe the behavior of the compass needle.

4. Turn the compass until the letter N is aligned

with the red end of the compass needle. This orientation represents a compass heading of "true" north. Tape the compass to the level surface to secure it in this position.

5. Insert one D-cell battery into the battery

holder.

6. Connect one end of the alligator clip lead to

one of the terminals of the battery holder.

Place the wire over the magnetic compass as

shown in Figure 9.

7. Attach the other end of the alligator clip lead

to the remaining battery holder terminal.

8. Observe what happens to the compass

needle.

9. Remove the alligator clip from the battery

holder.

10. Observe what happens to the compass

needle.Figure 9. continued on next page 10 Carolina Distance Learning

ACTIVITY 2

A Solenoid

This apparatus is a specialized electromagnet

known as a solenoid. These devices are used to activate switches, relays, valves, and power door locks.

1. Collect the straw, the magnet wire, a D-cell

battery, a battery holder, an alligator clip lead, and a paper clip.

2. Wind the magnet wire around the straw 100

times, leaving 8 cm on each end of the coil (see Figure 10).

Figure 10.

3. Use the sandpaper to remove the enamel

from the ends of the magnet wire. Ensure that the enamel is removed on all sides.

4. inside the straw.

5. Insert the D-cell battery into the battery

holder.

6. Connect the alligator clips to the bare ends of

the magnet wire coil.

7. Connect 1 alligator clip (along with the

magnet wire) to the terminal of the battery holder.

8. Place the straightened paper clip inside the

straw.

9. Place the straw with the straightened paper

clip on a level surface. Ensure that neither opening of the straw is pointed at yourself or anyone else.

10. Connect the remaining alligator clip (along

with the magnetic wire) to the other battery terminal.

11. Observe the motion of the paper clip.

12. Repeat the procedure several times, and

observe what happens to the paper clip. Try it with more and less of the paper clip inside the straw.

ACTIVITY 3

A Coiled Wire Electromagnet

1. Obtain the nail from the kit.

2. Use the same magnet wire-wrapped straw

from Activity 2.

3. Ensure that the enamel is removed from the

ends of the magnet wire.

4. Place the nail inside the straw that has the

magnet wire wrapped around it.

5. Connect a clip from each of 2 alligator clip

leads to the terminals of the battery holder.

6. Connect the open ends of the 2 alligator

clip leads to the stripped ends of the magnet wire. It may be necessary to fold the ends over or wrap the ends of the wire around the alligator clips to ensure a good connection. The coil and the nail are now an electromagnet.

7. Place the magnetic compass on a level

surface, and turn the compass so that the red end of the needle aligns with the letter N .

8. Place the electromagnet near the magnetic

compass. continued on next page www.carolina.com/distancelearning 11

ACTIVITY

ACTIVITY 3

continued

9. Observe what happens to the compass

needle.

10. Place the end of the nail next to the

magnetic compass to determine which end of the electromagnet is north and which end is south. The north end of the compass will be attracted to the south pole of the electromagnet.

11. Use a permanent marker to mark the north

pole of the nail.

12. Place several paper clips on a level surface.

13. Use the electromagnet to pick up as many

paper clips as possible. Count the number of paper clips the magnet is able to lift.

14. While holding the paper clips with the

electromagnet, disconnect one of the alligator clips from the battery holder.

15. Observe what happens to the paper clips.

16. Place the second D-cell battery in the

second battery holder.

17. Connect the batteries in series by

connecting the snap-connectors at the ends of the battery holders; connect the batteries to the electromagnet.18. Use the electromagnet to pick up as many paper clips as possible.

19. Count the number of paper clips picked up

by the electromagnet.

20. Disconnect the electromagnet, and remove

one of the batteries.

21. Remove the nail from the magnet wire coil.

22. Reattach the alligator clip lead to the battery

holder, reconnecting the electromagnet.

23. Using only the coil of wire, pick up as many

paper clips as possible. Count the number of paper clips the electromagnet is able to pick up.

24. Detach the alligator clip lead from the

battery holder as well as from one end of the magnet wire coil.

25. Reinsert the nail into the coil of wire.

26. Unwind the coil of wire to remove 50 coils

from around the nail.

27. Reattach the alligator clip lead to the

electromagnet and the battery terminal.

28. Use the electromagnet with 50 turns of wire

to pick up as many paper clips as possible.

29. Count the number of paper clips the

electromagnet is able to pick up. 12 Carolina Distance Learning

ACTIVITY 4

A DC Electric Motor

1. Obtain the coil created in the “Preparation"

section.

2. Wrap the ends of the wire through and

around the coil on opposite sides in opposite directions. When suspended by the straight ends of the wire, the coil should rest vertically (see Figure 11).

3. Use the sandpaper to remove the enamel

from the ends of the wire. Ensure that the wire is clear of enamel on all sides.

4. Obtain the 2 unwound paper clips from the

“Preparation" section. These paper clips will

act as the brush for the wire.

5. Place the foam cup upside down on a level

surface. Tape the 2 paper clips on opposite sides of the cup so the clips extend upward from the bottom side of the cup, providing a place for the wire coil to rest, supported by the straight ends of the wire (see Figure 11).

6. Place 2 or 3 ring magnets at the bottom of

the inverted foam cup.

7. Place the coil between the extended paper

clips so it is supported by the straight ends of the wire. The wire coil should be suspended above the magnets, as close to the magnets as possible, with enough space between the magnets and the coil so that the coil can turn.

8. Place a D-cell battery in a battery holder.

9. Connect the battery holder to the paper

clips using the 2 alligator clip leads. The coil should begin to turn. It may require a small

push to get it started.Note: For the motor to turn, the coil must be suspended above the magnets and perfectly balanced in a vertical orientation. Ensure that the coil is close to the magnets with enough room to turn and that the ends of the wire in contact with the paper clips are clear of enamel.

10. Observe the direction in which the coil

turns.

11. Disconnect the alligator clip leads from the

paper clips, and attach the leads to the opposite paper clips.

12. Observe the direction in which the coil

turns.

13. Disconnect one of the alligator clip leads

from the paper clips.

14. Turn the stack of ring magnets upside

down.

15. Reattach the alligator clip lead to the paper

clip.

16. Observe the direction in which the coil

turns.

17. Disconnect the alligator clips from the paper

clips.

Figure 11.

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ACTIVITY

ACTIVITY 5

A Electric Speaker

1. Arrange all the ring magnets into a single

stack.

2. Place the coil of magnet wire (created in the

“Preparation" section) on top of the stack

with the straight ends extending to either side.

3. Connect 1 alligator clip to each end of the

bare wire. It may be necessary to fold the wire over or wrap the ends of the wire around the alligator clip for a good connection.

4. Remove the housing of the audio jack by

turning it counterclockwise.

5. Insert one end of each of the hookup wires

through the housing, and connect the 2 bare ends to the 2 metal posts inside the plug.

Insert the wire through the hole and twist

it as tightly as you can against its terminal for good contact between the wire and its terminal post (see Figure 12). To ensure that the bare wires do not touch each other, add a small piece of nonconductive material (a small piece of paper, tape, or rubber band) between the posts to keep the two posts and their bare wires separate. Figure 12.6. Slide the housing over both wires, and tighten it by turning it clockwise.

7. Connect the audio jack to a music device

with an audio jack connection port.

8. Place the stack of magnets on a level

surface. Place the coil on top of the magnets (see Figure 13).

Figure 13.

9. Place the aluminum pie plate on top of the

metal stack. To keep the plate in place, you may try placing one of the ring magnets on the opposite surface.

10. Turn on the music device.

11. Listen closely to the pie plate. You may

need to put your ear close to the plate and keep background noise to a minimum.

12. Sprinkle a small amount of salt on the pie

plate. Observe the motion of the grains as the speaker plays. 14 Carolina Distance Learning

Disposal and Cleanup

1. Carefully unhook all electronics from wires.

2. Return all materials to the kit.

www.carolina.com/distancelearning 15 Note: For more information on electricity and magnetism, see the following links:

Electricity and Magnetism

https://www.carolina.com/teacher-resources/Interactive/electricity-and-magnetism/tr30175. tr?question=electricity%20and%20magnetism

Energy Is Energy

https://www.carolina.com/teacher-resources/Interactive/energy-is-energy/tr32420.tr?ques- tion=energy%20is%20energy Electrify Your Classroom with a Discussion on the War of the Currents,

Past and Present

https://www.carolina.com/teacher-resources/Interactive/electrify-your-classroom-with-a-dis- cussion-on-the-war-of-the-currents/tr25105.tr?question=war%20of%20current

PHYSICS

Magnetism

Investigation Manual

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