Physics
Current to Magnetic Field
Current to magnetic field refers to the relationship between an electric current and the magnetic field it generates. When an electric current flows through a conductor, it creates a magnetic field around the conductor. This phenomenon is described by Ampère's law and is fundamental to understanding electromagnetism and the behavior of electric currents in various devices and systems.
Written by Perlego with AI-assistance
Related key terms
1 of 5
7 Key excerpts on "Current to Magnetic Field"
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Learning Press(Publisher)
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. In view of special relativity, electric and magnetic fields are two interrelated aspects of a single object, called the electromagnetic field. A pure electric field in one reference frame is observed as a combination of both an electric field and a magnetic field in a moving reference frame. In quantum physics, this electromagnetic field is understood to be caused by virtual photons. Most often this quantum description is not needed because the simpler classical theory is sufficient. ________________________ WORLD TECHNOLOGIES ________________________ 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 electrical motors and generators. Magnetic forces give information about the charge carriers in a material through the Hall effect. The interaction of magnetic fields in electrical devices such as transformers is studied in the discipline of magnetic circuits. B and H Alternative names for B name used by magnetic flux density electrical engineers magnetic induction applied mathematicians electronics engineers magnetic field physicists Alternative names for H name used by magnetic field intensity electrical engineers magnetic field strength electronics engineers auxiliary magnetic field applied mathematicians magnetizing field physicists The term magnetic field is used for two different vector fields, denoted B and H .
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Academic Studio(Publisher)
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. In view of special relativity, electric and magnetic fields are two interrelated aspects of a single object, called the electromagnetic field. A pure electric field in one reference frame is observed as a combination of both an electric field and a magnetic field in a moving reference frame. In quantum physics, this electromagnetic field is understood to be caused by virtual photons. Most often this quantum description is not needed because the simpler classical theory is sufficient. ________________________ WORLD TECHNOLOGIES ________________________ 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. History One of the first drawings of a magnetic field, by René Descartes, 1644. It illustrated his theory that magnetism was caused by the circulation of tiny helical particles, threaded parts, through threaded pores in magnets. Although magnets and magnetism were known much earlier, one of the first descriptions of the magnetic field was produced in 1269 C.E.
eBook - PDF- James Shipman, Jerry Wilson, Charles Higgins, Bo Lou, James Shipman(Authors)
- 2020(Publication Date)
- Cengage Learning EMEA(Publisher)
Hence, the field lines are indications of the magnetic force, or a force field. ●● Figure 8.17a shows the mag- netic field lines around a simple bar magnet. The arrows in the field lines indicate the direction in which the north pole of a compass needle would point. The closer together the field lines, the stronger the magnetic force. Magnetic field patterns can be “seen” by using iron filings. The iron filings become magnetized and act as small compass needles. The outline of the magnetic field pro- duced in this manner is shown for the bar magnet in Fig. 8.17b. The field concept is analogous to an electric field around charges, but with iron filings the magnetic field is more easily visualized. The electric and magnetic fields are vector quantities, and elec- tromagnetic waves, as discussed in Chapter 6.3, are made up of electric and magnetic fields that vary with time. Electricity and magnetism are generally discussed together because they are linked. (Electromagnetism is the topic of section 8.5.) In fact, the source of magnetism is moving and “spinning” electrons. Hans Oersted, a Danish physicist, first discovered in 1820 that a compass needle is deflected by a wire carrying electric current. When a compass is placed near a wire in a simple battery circuit and the circuit is closed, there is current in the wire and the compass needle is deflected from its north-seeking direction. When the circuit is opened, the compass needle goes back to pointing north again. The strength of the magnetic field is directly proportional to the magnitude of the current: the greater the current, the greater the strength of the magnetic field. Hence, a current produces a magnetic field that can be turned off and on at will. Different configurations of current-carrying wires give different magnetic field config- urations. For example, a straight, dc current-carrying wire produces a field in a circular pattern around the wire (●● Fig. 8.18a).
eBook - PDF- David Halliday, Robert Resnick, Jearl Walker(Authors)
- 2021(Publication Date)
- Wiley(Publisher)
Key Ideas ● The magnetic field set up by a current-carrying con- ductor can be found from the Biot–Savart law. This law asserts that the contribution d B → to the field produced by a current-length element i d s → at a point P located a distance r from the current element is d B → = μ 0 ___ 4π id s → × r ̂ _______ r 2 (Biot–Savart law). Here r ̂ is a unit vector that points from the element toward P. The quantity μ 0 , called the permeability con- stant, has the value 4π × 10 −7 T · m/A ≈ 1.26 × 10 −6 T · m/A. ● For a long straight wire carrying a current i, the Biot– Savart law gives, for the magnitude of the magnetic field at a perpendicular distance R from the wire, B = μ 0 i ____ 2πR (long straight wire). ● The magnitude of the magnetic field at the center of a circular arc, of radius R and central angle ϕ (in radians), carrying current i, is B = μ 0 iϕ _____ 4πR (at center of circular arc). C H A P T E R 2 9 What Is Physics? One basic observation of physics is that a moving charged particle produces a magnetic field around itself. Thus a current of moving charged particles produces a magnetic field around the current. This feature of electromagnetism, which is the combined study of electric and magnetic effects, came as a surprise to the people who discovered it. Surprise or not, this feature has become enormously 887 29.1 MAGNETIC FIELD DUE TO A CURRENT important in everyday life because it is the basis of countless electromagnetic devices. For example, a magnetic field is produced in maglev trains and other devices used to lift heavy loads. Our first step in this chapter is to find the magnetic field due to the current in a very small section of current-carrying wire. Then we shall find the mag- netic field due to the entire wire for several different arrangements of the wire. Calculating the Magnetic Field Due to a Current Figure 29.1.1 shows a wire of arbitrary shape carrying a current i. We want to find the magnetic field B → at a nearby point P.
eBook - PDF- John D. Cutnell, Kenneth W. Johnson, David Young, Shane Stadler(Authors)
- 2018(Publication Date)
- Wiley(Publisher)
Analyzing Multiple-Concept Problems EXAMPLE 7 A Current Exerts a Magnetic Force on a Moving Charge Figure 21.26 shows a very long, straight wire carrying a current of 3.0 A. A particle has a charge of +6.5 × 10 −6 C and is moving parallel to the wire at a distance of 0.050 m. The speed of the particle is 280 m/s. Determine the magnitude and direction of the magnetic force exerted on the charged particle by the current in the wire. Reasoning The current generates a magnetic field in the space around the wire. The charged particle moves in the presence of this field and, therefore, can experience a magnetic force. The magnitude of this force is given by Equation 21.1, and the direction can be determined by applying RHR-1 (see Section 21.2). Note in Figure 21.26 that the magnetic field B → produced by the current lies in a plane that is perpendicular to both the wire and the velocity v → of the particle. Thus, the angle between B → and v → is θ = 90.0°. F v B q 0 B F v R.H. I FIGURE 21.26 The positive charge q 0 moves with a velocity v → and experiences a magnetic force F → because of the magnetic field B → produced by the current in the wire. 606 CHAPTER 21 Magnetic Forces and Magnetic Fields We have now seen that an electric current can create a magnetic field of its own. Ear- lier, we have also seen that an electric current can experience a force created by another magnetic field. Therefore, the magnetic field that one current creates can exert a force on another nearby current. Conceptual Example 8 deals with this magnetic interaction between currents. Modeling the Problem STEP 1 Magnetic Force on the Particle The magnitude F of the magnetic force acting on the charged particle is given at the right by Equation 21.1, where ∣q 0 ∣ is the magnitude of the charge, is the particle speed, B is the magnitude of the magnetic field produced by the wire, and is the angle between the particle velocity and the magnetic field.
- David Halliday, Robert Resnick, Jearl Walker(Authors)
- 2023(Publication Date)
- Wiley(Publisher)
LEARNING OBJECTIVES Fermilab/Science Source 826 CHAPTER 28 Magnetic Fields Magnetic Force on a Current-Carrying Wire We have already seen (in connection with the Hall effect) that a magnetic field exerts a sideways force on electrons moving in a wire. This force must then be transmitted to the wire itself, because the conduction electrons cannot escape sideways out of the wire. In Fig. 28.6.1a, a vertical wire, carrying no current and fixed in place at both ends, extends through the gap between the vertical pole faces of a mag- net. The magnetic field between the faces is directed outward from the page. In Fig. 28.6.1b, a current is sent upward through the wire; the wire deflects to the right. In Fig. 28.6.1c, we reverse the direction of the current and the wire deflects to the left. Figure 28.6.2 shows what happens inside the wire of Fig. 28.6.1b. We see one of the conduction electrons, drifting downward with an assumed drift speed v d . Equation 28.1.3, in which we must put ϕ = 90°, tells us that a force F → B of magni- tude ev d B must act on each such electron. From Eq. 28.1.2 we see that this force must be directed to the right. We expect then that the wire as a whole will expe- rience a force to the right, in agreement with Fig. 28.6.1b. If, in Fig. 28.6.2, we were to reverse either the direction of the magnetic field or the direction of the current, the force on the wire would reverse, being directed now to the left. Note too that it does not matter whether we consider negative charges drifting downward in the wire (the actual case) or positive charges drifting upward. The direction of the deflecting force on the wire is the same. We are safe then in dealing with a current of positive charge, as we usually do in dealing with circuits. Find the Force. Consider a length L of the wire in Fig. 28.6.2. All the conduc- tion electrons in this section of wire will drift past plane xx in Fig.
eBook - PDF- John D. Cutnell, Kenneth W. Johnson, David Young, Shane Stadler(Authors)
- 2021(Publication Date)
- Wiley(Publisher)
When a current I exists in a coil of wire with N turns, each of area A, in the presence of a magnetic field of magni- tude B, the coil experiences a net torque that has a magnitude given by Equation 21.4, where is the angle between the direction of the magnetic field and the normal to the plane of the coil. The quantity NIA is known as the magnetic moment of the coil. τ = NIAB sin ϕ (21.4) 21.7 Magnetic Fields Produced by Currents An electric current produces a magnetic field, with different current geometries giving rise to different field patterns. For an infinitely long, straight wire, the mag- netic field lines are circles centered on the wire, and their direction is given by Right-Hand Rule No. 2 (see below). The magnitude of the mag- netic field at a radial distance r from the wire is given by Equation 21.5, where I is the current in the wire and 0 is a constant known as the permeability of free space ( μ 0 = 4π × 10 −7 T · m/A). B = μ 0 I _ 2πr (21.5) Focus on Concepts 683 Right-Hand Rule No. 2: Curl the fingers of the right hand into the shape of a half-circle. Point the thumb in the direction of the con- ventional current I, and the tips of the fingers will point in the direc- tion of the magnetic field → B . The magnitude of the magnetic field at the center of a flat circu- lar loop consisting of N turns, each of radius R and carrying a current I, is given by Equation 21.6. B = N μ 0 I _ 2R (21.6) The loop has associated with it a north pole on one side and a south pole on the other side. The side of the loop that behaves like a north pole can be predicted by using Right-Hand Rule No. 3: Curl the fingers of the right hand along the direction of the conven- tional current I around the loop or solenoid, and the thumb will point in the direction of the magnetic field at the center of the loop, or everywhere inside the solenoid, and toward their respec- tive north poles.
Index pages curate the most relevant extracts from our library of academic textbooks. They’ve been created using an in-house natural language model (NLM), each adding context and meaning to key research topics.
