Physics
Magnetic Fields
Magnetic fields are regions around a magnet or current-carrying conductor where magnetic forces are experienced. They exert forces on other magnets and moving charges, and their strength and direction can be represented by magnetic field lines. The Earth also has a magnetic field, which is important for navigation and protects the planet from solar wind.
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12 Key excerpts on "Magnetic Fields"
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Orange Apple(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter- 4 Magnetic Field A magnetic field is a field of force produced by moving electric charges, by electric fields that vary in time, and by the 'intrinsic' magnetic field of elementary particles associated with the spin of the particle. There are two separate but closely related fields to which the name 'magnetic field' can refer: a magnetic B field and a magnetic H field. The magnetic field at any given point is specified by both a direction and a magnitude (or strength); as such it is a vector field. The magnetic field is most commonly defined in terms of the Lorentz force it exerts on moving electric charges. The relationship between the magnetic and electric fields, and the currents and charges that create them, is described by the set of Maxwell's equations. In special relativity, electric and Magnetic Fields are two interrelated aspects of a single object, called the electromagnetic field tensor; the aspect of the electromagnetic field that is seen as a magnetic field is dependent on the reference frame of the observer. In quantum physics, the electromagnetic field is quantized and electromagnetic interactions result from the exchange of photons. Magnetic Fields have had many uses in ancient and modern society. The Earth produces its own magnetic field, which is important in navigation since the north pole of a compass points toward the south pole of Earth's magnetic field, located near the Earth's geographical north. Rotating Magnetic Fields are utilized in both electric motors and generators. Magnetic forces give information about the charge carriers in a material through the Hall effect. The interaction of Magnetic Fields in electric devices such as transformers is studied in the discipline of magnetic circuits. ________________________ WORLD TECHNOLOGIES ________________________ History One of the first drawings of a magnetic field, by René Descartes, 1644.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Learning Press(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter- 9 Magnetic Field A magnetic field is a field of force produced by moving electric charges, by electric fields that vary in time, and by the 'intrinsic' magnetic field of elementary particles associated with the spin of the particle. There are two separate but closely related fields to which the name 'magnetic field' can refer: a magnetic B field and a magnetic H field. The magnetic field at any given point is specified by both a direction and a magnitude (or strength); as such it is a vector field. The magnetic field is most commonly defined in terms of the Lorentz force it exerts on moving electric charges. The relationship between the magnetic and electric fields, and the currents and charges that create them, is described by the set of Maxwell's equations. In special relativity, electric and Magnetic Fields are two interrelated aspects of a single object, called the electromagnetic field tensor; the aspect of the electromagnetic field that is seen as a magnetic field is dependent on the reference frame of the observer. In quantum physics, the electromagnetic field is quantized and electromagnetic interactions result from the exchange of photons. Magnetic Fields have had many uses in ancient and modern society. The Earth produces its own magnetic field, which is important in navigation since the north pole of a compass points toward the south pole of Earth's magnetic field, located near the Earth's geographical north. Rotating Magnetic Fields are utilized in both electric motors and generators. Magnetic forces give information about the charge carriers in a material through the Hall effect. The interaction of Magnetic Fields in electric devices such as transformers is studied in the discipline of magnetic circuits. ________________________ WORLD TECHNOLOGIES ________________________ History One of the first drawings of a magnetic field, by René Descartes, 1644.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Academic Studio(Publisher)
______________________________ WORLD TECHNOLOGIES ______________________________ Chapter- 8 Magnetic Field A magnetic field is a field of force produced by moving electric charges, by electric fields that vary in time, and by the 'intrinsic' magnetic field of elementary particles associated with the spin of the particle. There are two separate but closely related fields to which the name 'magnetic field' can refer: a magnetic B field and a magnetic H field. The magnetic field at any given point is specified by both a direction and a magnitude (or strength); as such it is a vector field. The magnetic field is most commonly defined in terms of the Lorentz force it exerts on moving electric charges. The relationship between the magnetic and electric fields, and the currents and charges that create them, is described by the set of Maxwell's equations. In special relativity, electric and Magnetic Fields are two interrelated aspects of a single object, called the electromagnetic field tensor; the aspect of the electromagnetic field that is seen as a magnetic field is dependent on the reference frame of the observer. In quantum physics, the electromagnetic field is quantized and electromagnetic interactions result from the exchange of photons. Magnetic Fields have had many uses in ancient and modern society. The Earth produces its own magnetic field, which is important in navigation since the north pole of a compass points toward the south pole of Earth's magnetic field, located near the Earth's geographical north. Rotating Magnetic Fields are utilized in both electric motors and generators. Magnetic forces give information about the charge carriers in a material through the Hall effect. The interaction of Magnetic Fields in electric devices such as transformers is studied in the discipline of magnetic circuits. ______________________________ WORLD TECHNOLOGIES ______________________________ History One of the first drawings of a magnetic field, by René Descartes, 1644.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Learning Press(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter- 3 Magnetic Field A magnetic field is a field of force produced by a magnetic object or particle, or by a changing electrical field and is detected by the force it exerts on other magnetic materials and moving electric charges. The magnetic field at any given point is specified by both a direction and a magnitude (or strength); as such it is a vector field. The complex mathematics underlying the magnetic field of an object is usually illustrated using magnetic field lines. These lines are strictly a mathematical concept and do not exist physically. Nonetheless, certain physical phenomena, such as the alignment of iron filings in a magnetic field, produces lines in a similar pattern to the imaginary magnetic field lines of the object. Magnets exert forces and torques on each other through the Magnetic Fields they create. Electric currents and moving electrical charges produce Magnetic Fields. Even the ma-gnetic field of a magnetic material can be modeled as being due to moving electrical charges. Magnetic Fields also exert forces on moving electrical charges. The Magnetic Fields within and due to magnetic materials can be quite complicated and is described using two separate fields which can be both called a magnetic field : a magnetic B field and a magnetic H field. Energy is needed to create a magnetic field. This energy can be reclaimed when the field is destroyed and, therefore, can be considered as being stored in the magnetic field. The value of this energy depends on the values of both B and H . An electric field is a field created by an electrical charge and such fields are intimately related to Magnetic Fields; a changing magnetic field generates an electric field and a changing electric field produces a magnetic field. The full relationship between the electric and Magnetic Fields, and the currents and charges that create them, is described by the set of Maxwell's equations.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Academic Studio(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter 9 Magnetic Field A magnetic field is a field of force produced by a magnetic object or particle, or by a changing electric field and is detected by the force it exerts on other magnetic materials and moving electric charges. The magnetic field at any given point is specified by both a direction and a magnitude (or strength); as such it is a vector field. The complex mathematics underlying the magnetic field of an object is usually illustrated using magnetic field lines. These lines are strictly a mathematical concept and do not exist physically. Nonetheless, certain physical phenomena, such as the alignment of iron filings in a magnetic field, produces lines in a similar pattern to the imaginary magnetic field lines of the object. Magnets exert forces and torques on each other through the Magnetic Fields they create. Electric currents and moving electric charges produce Magnetic Fields. Even the magnetic field of a magnetic material can be modeled as being due to moving electric charges. Magnetic Fields also exert forces on moving electric charges. The Magnetic Fields within and due to magnetic materials can be quite complicated and is described using two separate fields which can be both called a magnetic field : a magnetic B field and a magnetic H field. Energy is needed to create a magnetic field. This energy can be reclaimed when the field is destroyed and, therefore, can be considered as being stored in the magnetic field. The value of this energy depends on the values of both B and H . An electric field is a field created by an electric charge and such fields are intimately related to Magnetic Fields; a changing magnetic field generates an electric field and a changing electric field produces a magnetic field. The full relationship between the electric and Magnetic Fields, and the currents and charges that create them, is described by the set of Maxwell's equations.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Library Press(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter- 4 Magnetic Field A magnetic field is a field of force produced by a magnetic object or particle, or by a changing electric field an d is detected by the force it exerts on other magnetic materials and moving electric charges. The magnetic field at any given point is specified by both a direction and a magnitude (or strength); as such it is a vector field. The complex mathematics underlying the magnetic field of an object is usually illustrated using magnetic field lines. These lines are strictly a mathematical concept and do not exist physically. Nonetheless, certain physical phenomena, such as the alignment of iron filings in a magneti c field, produces lines in a similar pattern to the imaginary magnetic field lines of the object. Magnets exert forces and torques on each other through the Magnetic Fields they create. Electric currents and moving electric charges produce Magnetic Fields. Even the magnetic field of a magnetic material can be modeled as being due to moving electric charges. Magnetic Fields also exert forces on moving electric charges. The Magnetic Fields within and due to magnetic materials can be quite complicated and is d escribed using two separate fields which can be both called a magnetic field : a magnetic B field and a magnetic H field. Energy is needed to create a magnetic field. This energy can be reclaimed when the field is destroyed and, therefore, can be considered as being stored in the magnetic field. The value of this energy depends on the values of both B and H . An electric field is a field created by an electric charge and such fields are intimately related to Magnetic Fields; a changing magnetic field genera tes an electric field and a changing electric field produces a magnetic field. The full relationship between the electric and Magnetic Fields, and the currents and charges that create them, is described by the set of Maxwell's equations.
eBook - PDF- William Moebs, Samuel J. Ling, Jeff Sanny(Authors)
- 2016(Publication Date)
- Openstax(Publisher)
Recycling facilities employ magnets to separate iron from other refuse. Research into using magnetic containment of fusion as a future energy source has been continuing for several years. Magnetic resonance imaging (MRI) has become an important diagnostic tool in the field of medicine, and the use of magnetism to explore brain activity is a subject of contemporary research and development. The list of applications also includes computer hard drives, tape recording, detection of inhaled asbestos, and levitation of high-speed trains. Magnetism is involved in the structure of atomic energy levels, as well as the motion of cosmic rays and charged particles trapped in the Van Allen belts around Earth. Once again, we see that all these disparate phenomena are linked by a small number of underlying physical principles. 11.2 | Magnetic Fields and Lines Learning Objectives By the end of this section, you will be able to: • Define the magnetic field based on a moving charge experiencing a force • Apply the right-hand rule to determine the direction of a magnetic force based on the motion of a charge in a magnetic field • Sketch magnetic field lines to understand which way the magnetic field points and how strong it is in a region of space We have outlined the properties of magnets, described how they behave, and listed some of the applications of magnetic properties. Even though there are no such things as isolated magnetic charges, we can still define the attraction and repulsion of magnets as based on a field. In this section, we define the magnetic field, determine its direction based on the right-hand rule, and discuss how to draw magnetic field lines. Defining the Magnetic Field A magnetic field is defined by the force that a charged particle experiences moving in this field, after we account for the gravitational and any additional electric forces possible on the charge.
eBook - PDF- David Halliday, Robert Resnick, Jearl Walker(Authors)
- 2021(Publication Date)
- Wiley(Publisher)
Key Ideas ● When a charged particle moves through a magnetic field B → , a magnetic force acts on the particle as given by F → B = q ( v → × B → ), where q is the particle’s charge (sign included) and v → is the particle’s velocity. ● The right-hand rule for cross products gives the direction of v → × B → . The sign of q then determines whether F → B is in the same direction as v → × B → or in the opposite direction. ● The magnitude of F → B is given by F B = |q|vB sin ϕ, where ϕ is the angle between v → and B → . Magnetic Fields What Is Physics? As we have discussed, one major goal of physics is the study of how an electric field can produce an electric force on a charged object. A closely related goal is the study of how a magnetic field can produce a magnetic force on a (moving) charged particle or on a magnetic object such as a magnet. You may already have a hint of what a magnetic field is if you have ever attached a note to a refrigerator door with a small magnet or accidentally erased a credit card by moving it near a magnet. The magnet acts on the door or credit card via its magnetic field. The applications of Magnetic Fields and magnetic forces are countless and changing rapidly every year. Here are just a few examples. For decades, the 851 28.1 Magnetic Fields AND THE DEFINITION OF B → entertainment industry depended on the magnetic recording of music and images on audiotape and videotape. Although digital technology has largely replaced magnetic recording, the industry still depends on the magnets that control CD and DVD players and computer hard drives; magnets also drive the speaker cones in headphones, TVs, computers, and telephones. A modern car comes equipped with dozens of magnets because they are required in the motors for engine igni- tion, automatic window control, sunroof control, and windshield wiper control. Most security alarm systems, doorbells, and automatic door latches employ mag- nets.
eBook - PDF- John D. Cutnell, Kenneth W. Johnson, David Young, Shane Stadler(Authors)
- 2018(Publication Date)
- Wiley(Publisher)
LEARNING OBJECTIVES After reading this module, you should be able to... 21.1 Define magnetic field. 21.2 Calculate the magnetic force on a moving charge in a magnetic field. 21.3 Analyze the motion of a charged particle in a magnetic field. 21.4 Describe how the masses of ions are determined using a mass spectrometer. 21.5 Calculate the magnetic force on a current in a magnetic field. 21.6 Calculate the torque on a current- carrying coil. 21.7 Calculate Magnetic Fields produced by currents. 21.8 Apply Ampère’s law to calculate the magnetic field due to a steady current. 21.9 Describe magnetic materials. Suranga Weeratunga/123RF. com CHAPTER 21 Magnetic Forces and Magnetic Fields This beautiful display of light in the sky is known as the northern lights (aurora borealis). It occurs when charged particles, streaming from the sun, become trapped by the earth’s magnetic field. The particles collide with molecules in the upper atmosphere, and the result is the production of light. Magnetic forces and Magnetic Fields are the subjects of this chapter. 21.1 Magnetic Fields Permanent magnets have long been used in navigational compasses. As Figure 21.1 illustrates, the compass needle is a permanent magnet supported so it can rotate freely in a plane. When the compass is placed on a horizontal surface, the needle rotates until one end points approximately to the north. The end of the needle that points north is labeled the north magnetic pole; the opposite end is the south magnetic pole. Magnets can exert forces on each other. Figure 21.2 shows that the magnetic forces between north and south poles have the property that like poles repel each other, and unlike poles attract. This behavior is similar to that of like and unlike electric charges. However, there is a significant difference between magnetic poles and electric charges. It is possible to separate positive from negative electric charges and produce isolated charges of either kind.
eBook - PDF- John D. Cutnell, Kenneth W. Johnson, David Young, Shane Stadler(Authors)
- 2015(Publication Date)
- Wiley(Publisher)
Like the electric field, the magnetic field has both a magnitude and a direction. We postpone a dis- cussion of the magnitude until Section 21.2, concentrating our attention here on the Chapter | 21 LEARNING OBJECTIVES After reading this module, you should be able to... 21.1 | Define magnetic field. 21.2 | Calculate the magnetic force on a moving charge in a magnetic field. 21.3 | Analyze the motion of a charged particle in a magnetic field. 21.4 | Describe how the masses of ions are determined using a mass spectrometer. 21.5 | Calculate the magnetic force on a current in a magnetic field. 21.6 | Calculate the torque on a current- carrying coil. 21.7 | Calculate Magnetic Fields produced by currents. 21.8 | Apply Ampère’s law to calculate the magnetic field due to a steady current. 21.9 | Describe magnetic materials. 518 Suranga Weeratunga/123RF. com S N Figure 21.1 The needle of a compass is a permanent magnet that has a north magnetic pole (N) at one end and a south magnetic pole (S) at the other. Like poles repel (a) Unlike poles attract (b) Figure 21.2 Bar magnets have a north magnetic pole at one end and a south magnetic pole at the other end. (a) Like poles repel each other, and (b) unlike poles attract. 21.1 | Magnetic Fields 519 direction. The direction of the magnetic field at any point in space is the direction indicated by the north pole of a small compass needle placed at that point. In Fig- ure 21.3 the compass needle is symbolized by an arrow, with the head of the arrow representing the north pole. The drawing shows how compasses can be used to map out the magnetic field in the space around a bar magnet. Since like poles repel and unlike poles attract, the needle of each compass becomes aligned relative to the magnet in the manner shown in the picture. The compass needles provide a visual picture of the magnetic field that the bar magnet creates. To help visualize the electric field, we introduced electric field lines in Section 18.7.
eBook - PDF- John D. Cutnell, Kenneth W. Johnson, David Young, Shane Stadler(Authors)
- 2021(Publication Date)
- Wiley(Publisher)
However, in order to take advantage of the wire’s superconducting properties, it must be cooled to temperatures close to absolute zero (0 K) by submersing it in liquid helium. Concept Summary 21.1 Magnetic Fields A magnet has a north pole and a south pole. The north pole is the end that points toward the north mag- netic pole of the earth when the magnet is freely suspended. Like magnetic poles repel each other, and unlike poles attract each other. A magnetic field exists in the space around a magnet. The magnetic field is a vector whose direction at any point is the direction indicated by the north pole of a small compass needle placed at that point. As an aid in visualizing the magnetic field, magnetic field lines are drawn in the vicinity of a magnet. The lines appear to originate from the north pole and end on the south pole. The magnetic field at any point in space is tangent to the magnetic field line at the point. Furthermore, the strength of the magnetic field is proportional to the number of lines per unit area that passes through a surface oriented perpendicular to the lines. 21.2 The Force That a Magnetic Field Exerts on a Moving Charge The direction of the magnetic force acting on a charge mov- ing with a velocity → v in a magnetic field → B is perpendicular to both → v and → B . For a positive charge the direction can be determined with the aid of Right-Hand Rule No. 1 (see below). The magnetic force on a mov- ing negative charge is opposite to the force on a moving positive charge. Right-Hand Rule No. 1: Extend the right hand so the fingers point along the direction of the magnetic field → B and the thumb points along the velocity → v of the charge. The palm of the hand then faces in the direction of the magnetic force → F that acts on a positive charge.
eBook - PDF- John D. Cutnell, Kenneth W. Johnson, David Young, Shane Stadler(Authors)
- 2015(Publication Date)
- Wiley(Publisher)
(b) Bars 1 and 3 will either be attracted to or repelled from each other, while bars 2 and 3 will always be attracted to each other. (c) Bars 1 and 3 will always be repelled from each other, while bars 2 and 3 will either be attracted to or repelled from each other. (d) Bars 1 and 3 will always be attracted to each other, while bars 2 and 3 will either be attracted to or repelled from each other. Guideway Rail Arm Guideway (b) (a) Levitation electromagnet S N S N N S N Figure 21.41 (a) The Transrapid maglev (a German train) has achieved speeds of 110 m/s (250 mph). The levitation electromagnets are drawn up toward the rail in the guideway, levitating the train. (b) The magnetic propulsion system. CONCEPT SUMMARY 21.1 Magnetic Fields A magnet has a north pole and a south pole. The north pole is the end that points toward the north magnetic pole of the earth when the magnet is freely suspended. Like magnetic poles repel each other, and unlike poles attract each other. A magnetic field exists in the space around a magnet. The magnetic field is a vector whose direc- tion at any point is the direction indicated by the north pole of a small compass needle placed at that point. As an aid in visualizing the magnetic field, magnetic field lines are drawn in the vicinity of a magnet. The lines appear to originate from the north pole and end on the south pole. The magnetic field at any point in space is tangent to the magnetic field line at the point. Furthermore, the strength of the magnetic field is proportional to the number of lines per unit area that passes through a surface oriented perpendicular to the lines. 21.2 The Force That a Magnetic Field Exerts on a Moving Charge The direction of the magnetic force acting on a charge moving with a velocity v B in a magnetic field B B is perpendicular to both v B and B B . For a positive charge the direction can be determined with the aid of Right-Hand Rule No.
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