Teacher Guides of the Lesson

Theoretical material for the lesson, definitions for concepts 

GROUP 1: Neodymium magnets

The Top 11 Uses for Neodymium Magnets

Neodymium magnets are incredibly diverse and you can find them across many industries. Here are the 11 most common places we see then.

Magnets are everywhere around you, giving helping hand to thousand of items in your everyday life. How many of these do you use?

1. Magnetic Resonance Imaging

MRIs are medical imaging devices that interact with your body on the tiniest of levels. The magnets affect the electrons in each atom of your body, then captures an image of the effect. The effect is varied depending on the type of tissue, giving a useful diagnostic image the medical field often relies on.

2. Magnotherapy

The scientific jury's not out on this one yet, but the number of people who swear by magnetic therapy is staggering. In magnotherapy, patients subject part of their body to a magnetic field by wearing magnetic jewelry or using other items on a regular basis, leading to (they say) pain relief, increased blood flow, or one of many other claims.

3. Audio Equipment

Speakers are controlled by two magnets and an electric current. A mobile electromagnetic coil is suspended near a fixed magnet, and an electric current is pushed through the coil very quickly. As the coil is charged, it is attracted to the magnet and repelled again, causing vibrations that are amplified and become music to your ears.

4. Lifting Large Loads

Magnets are used in many fields to lift things, from collecting dropped metal pieces, to moving cars, to recovering sunken metal vehicles from underwater. Their lack of moving parts and extreme lifting capacity makes magnets a practical choice. The only hitch -it only works on ferromagnetic items.

5. Flying

OK, levitation. But the use of magnets to make objects levitate is just as cool. This technology is currently being experimented with for applications from hoverboards to efficient vehicles, as well and moving industrial parts. And you can easily find plans for hovering toys that use small magnets online.

6. Business Displays and Signage

More and more businesses are relying on magnets to hold their signs in place and attract customers. In store displays often require less preparation of surfaces -and in many building (such as offices) with metal walls or dividers, no preparation. Magnets are also used as a solution for company vehicles, causing no damage to paint and requiring only peeling off.

7. Do-It-Yourself Projects

Both large and (particularly) small magnets can be found all around the modern home, and DIYers are embracing their usefulness. Used often in cabinetry and sliding parts, they can also be used a less permanent way to ensure a part says put, until you want it to move.

8. Home and Wall Decor

Do you love to redecorate on a whim but hate the work of patching and re-drilling every time you want to change your wall art? Magnets of impressively small sizes can by used to hold heavy decorative items, making them easy to switch or replace when you want a change.

9. Stationery and Business Supplies

Who doesn't look harder at a business card or flyer with a nifty design? The same holds true for other printed items. Discreet closures for books and planners, securing a lid, or helping someone keep track of your menu on their fridge are just some of the ways the tiniest of magnets can help.

10. Jewelry

Magnets are everywhere in jewelry. The most convenient clasps are made from magnets and piercing free earrings depend on them. Recently, many interesting chains that use magnets to morph from bracelet to necklace quickly have been flooding stores.

11. Hobbies

Magnets are just handy, and nowhere is that more apparent than in crafts and hobbies. Standing up your figurines or making the parts to a project movable require only the tiniest of magnets.

GROUP 2: Magnetic sensors

Magnetic Sensors and Their Applications

Magnetic sensors can be split into two different types of sensor. This depends on whether they measure the vector components or the total magnetic field. While the results of each sensor vary, the techniques used to create these magnetic sensors use similar aspects of physics and electronic theories. All magnetic sensors work with the Earth’s magnetic field.

The most common technologies used to create these magnetic sensors are the coil, fluxgate, optically pumped, nuclear precession, SQUID, Hall-effect, anisotropic magnetoresistance, giant magnetoresistance, magnetic tunnel junctions, giant magnetoimpedance, piezoelectric composites, magnetodiode, magnetotransistor, fiber optic, magnetooptic as well as microelectromechanical systems-based magnetic sensors.

The reason for the many different types of magnetic sensor is because of the wide range of applications that each sensor has. Some of these industrial applications include linear, angular position and rotation sensing. It is for this reason that contactless sensors are particularly popular.

Magnetic sensors have been developed by companies, such as Crocus, to have high sensitivity, low power consumption as well as having specific design functions depending on the application. This includes high-temperature operation and high-frequency operation. This allows the user to have a reliable and durable magnetic sensor for optimal performance.

There are many different industries in which magnetic sensors are particularly useful. Below is a list of some of the areas that can be benefited from magnetic sensor application.

Power Distribution Units (PDU’s)

Cloud computing and large data analytics is an increasingly large area of new industry. Because of this, there has been an increased production of power distribution units which are the main part of data centers and large servers. Data center infrastructure needs PDU’s to supply AC or DC electrical power to the servers. Magnetic sensors help the PDU provide power filtering to the server and intelligent load balancing. They can also be remotely monitored.

Robotics and Factory Automation

Another recent area of industrial growth is in robotics and the adoption of robotics for factory automation. Magnetic sensors, particularly linear and angular position sensing play a large part in keeping machines in the factory running smoothly. The magnets are used to monitor the motor movements of the robots in terms of precision and accuracy. As the demand rises for faster and more efficient production lines, the role of the magnetic sensor has also evolved to include the use of safety switches and proximity detection.

Energy and Water Appliances

While magnetic sensors are usually used in high tech industries, they can also be used in some of the worlds oldest infrastructure. The sensors can be used for energy and water conservation through intelligent, open/close door detection, fluid levels and contactless sensing. This allows companies to comply with newly updated regulatory standards. In addition to this, this type of sensor can be used on regular appliances such as vacuum cleaners and refrigerators.

Green Energy

Magnetic sensors can be a critical part of contactless current, angular position and switch sensing for green energy power plants such as wind turbines and solar panel farms. Angular position sensing is particularly important for allowing optimal wind power generation while solar combiner boxes benefit from contactless current sensors.

GROUP 3: Magnetic seismographs

What is a Seismometer?

From Wikipedia: Seismometers are instruments that measure motions of the ground, including those of seismic waves generated by earthquakes, nuclear explosions, and other seismic sources. Records of seismic waves allow seismologists to map the interior of the Earth, and locate and measure the size of these different sources.

Basically, it's an instrument that measures motion.  You place it somewhere that is sturdy and doesn't move, and it will measure any motion from earthquakes, etc.

How does it work?

Each seismometer shown measures movement in only one direction, or along one axis.  Professional seismic observatories usually have three individual instruments measuring three axes: north-south, east-west, and the vertical. If only one axis can be measured, this is usually the vertical because it is less noisy and gives better records of some seismic waves.

Ted's seismometers are based on a number of typical methods.  You can find many descriptions by searching for, "Lehman Seismometer."  They consist of a heavy weight on a long arm that has a natural frequency with a long time period.  That is, if you pull it off-center and let go, it takes many seconds for it to cycle up and down, back to the stable center-point.

The sensor consists of a coil of magnet wire on the stationary base, with a pair of strong neodymium magnets on the movable arm.  The coil is made from single-strand copper wire that has a thin layer of insulation.  It's often used in transformers and coils in electronic devices.  A coil is wound with several thousand loops of thin wire.

When the magnet moves, the magnetic field in the coil of wire changes.  Thanks to basic physics, a changing magnetic field in a wire causes a current that can be measured.  The wires of the coil are typically hooked up to an amplifier (because the changes are very small) and an analog-to-digital converter that lets you view the information on a PC.

In the animation at right, the stationary base is blue.  It is made from a non-ferromagnetic material like aluminum.  Magnets don't stick to it.

The orange arm is hinged at the left, and holds the big, heavy counterweight shown in green.  A steel cable to the top of the structure provides support for the arm.

There are two items sticking up from the blue, stationary base.  The one at the left holds a coil of magnet wire, shown in red.  Notice that the arm holds two magnets, above and below the coil.  They are oriented such that they are attracting towards one another, which makes a strong, uniform field between them.  When the magnets move, the field in the coil of wire changes.

To the right of the coil is a piece of aluminum sticking up, also surrounded by a pair of magnets.  Why?  The whole system needs some damping, or something that will make it eventually stop.  When something moves the arm, it could wobble back and forth for a long, long time if the hinge point has minimal friction.  By projecting a strong magnetic field into a piece of aluminum, eddy currents flow in the aluminum when the arm moves.  This gradually slows it down, acting as a gentle break to motion.

In older seismometers, a paddle was often placed in a liquid bath containing water or oil.  The drag of the paddle moving through the liquid would slow it down, dampening the motion.  Since the level of the liquid requires maintenance, the method of using eddy currents can be much more consistent and maintenance free.

Not shown are the two wires dangling off the coil of magnet wire, which gets hooked to to some device to read the changes in current.  Before inexpensive PCs were so accessible, this used to be recorded on a chart recorder.  Today, an amplifier and an A-to-D (analog to digital) device sends the information to a PC.  There are various software packages available for handling the data (see below).

GROUP 4: Metal detectors

A metal detector is an electronic instrument which detects the presence of metal nearby. Metal detectors are useful for finding metal inclusions hidden within objects, or metal objects buried underground. They often consist of a handheld unit with a sensor probe which can be swept over the ground or other objects. If the sensor comes near a piece of metal this is indicated by a changing tone in earphones, or a needle moving on an indicator. Usually the device gives some indication of distance; the closer the metal is, the higher the tone in the earphone or the higher the needle goes. Another common type are stationary "walk through" metal detectors used for security screening at access points in prisons, courthouses, and airports to detect concealed metal weapons on a person's body.

The simplest form of a metal detector consists of an oscillator producing an alternating current that passes through a coil producing an alternating magnetic field. If a piece of electrically conductive metal is close to the coil, eddy currents will be induced in the metal, and this produces a magnetic field of its own. If another coil is used to measure the magnetic field (acting as a magnetometer), the change in the magnetic field due to the metallic object can be detected.

The first industrial metal detectors were developed in the 1960s and were used extensively for mineral prospecting and other industrial applications. Uses include detecting land mines, the detection of weapons such as knives and guns (especially in airport security), geophysical prospecting, archaeology and treasure hunting. Metal detectors are also used to detect foreign bodies in food, and in the construction industry to detect steel reinforcing bars in concrete and pipes and wires buried in walls and floors.

Instructions for demonstrations and safety

Warning: experiments should be performed under the supervision of teachers or students follow the instructions of safety procedures.

Additional guidelines for organizing a lesson 

1.      Organization moment. Establishing emotional state. Checking for absent students.

2.      Teacher introduces the topic and objectives of the lesson, assess criteria.

3.      Teacher asks Groups 1, 3 and 4 present an Applications of Magnetic Materials for different devices as a presentation / posters. They also discuss the tendency of their application. Assessment criteria should be agreed in advance.

4.      Groups assess each other’s work and provide fair and helpful feedback by using a assessment criteria.

5.      Teacher asks learners to answer a Quick Quiz questions individually.

6.      At the end of the lesson students are encouraged to reflect on what they have learned and

               what they need to improve.

Recommendations for formative assessment

 Activity1. Students discuss learning objectives and assess criteria.

 Activity2. Groups 1, 3 and 4 present an Applications of Magnetic Materials for different

                  devices as a presentation / posters. They also discuss the tendency of their

                  application. Assessment criteria should be agreed in advance.

 Activity3. Groups assess each other’s work and provide fair and helpful feedback by using a

                  assessment criteria.

 Activity4. Learners answer a Quick Quiz questions individually. Students assess each other’s

                  work by using answer sheet and provide fair and helpful feedback.

 Activity5. At the end of the lesson students are encouraged to reflect on what they have learned

                 and what they need to improve.

Answers, criteria for assignments, additional materials for the lesson

Criteria for assignments:

·         Describe at least five applications of Neodymium magnets;

·         Describe at least three applications of Magnetic sensors;

·         Describe at least three applications of Metal detectors;

·         Describe the working principle of  Magnetic seismographs;

·         Analyse the modern device’s applications  by using magnetic materials;

·         Recall the tendency of each device’s applications;

Answer

Part 1

1-A

2-D

3-B

Part 2

1.      Why Neodymium magnets are so strong?

       Neodymium magnets are considered strong because they resist

       demagnetization and have a high saturation magnetization. ... When a

       crystal has one easy axis of magnetization, the coercivity, or resistance

       to demagnetization, of the material increases because more energy is

       required to change the direction of magnetization.

2.      What is the use of magnetic sensor?

Magnetic sensors are used in many industrial applications for contactless currentsensing, linear and angular position, and rotation sensing. Crocus' magnetic sensors are designed to provide superior performance in all of these applications.

3.      What is the use of Magnets in a seismograph?

Magnet is used in most high-tech seismographs used by scientists in order to accurately and precisely measure the smallest ripples in the earth caused by earthquakes.

List of useful links and literature

Douglas C. Giancoli, Physics Principles with Applications, Seventh edition  2014.

Keith Johnson Physics for You IGCSE Updated Edition 2011

Скачано с www.znanio.ru