What is the value of force on a closed circuit in a magnetic field

Electromagnetic Forces and Fields The magnetic field of naturally occurring magnetite is too weak to be used in devices such as modern motors and generators; these magnetic fields must come from electric currents. Magnetic fields affect moving charges, and moving charges produce magnetic fields; therefore, the concepts of magnetism and electricity are closely intertwined. Magnetic fields and lines of force A bar magnet attracts iron objects to its ends, called poles. One end is the north pole, and the other is the south pole. If the bar is suspended so that it is free to move, the magnet will align itself so that its north pole points to the geographic north of the earth. The suspended bar magnet acts like a compass in the earth's magnetic field. If two bar magnets are brought close together, the like poles will repel each other, and the unlike poles attract each other. ( Note: By this definition, the magnetic pole under the earth's north geographical pole is the south pole of the earth's magnetic field.) This magnetic attraction or repulsion can be explained as the effect of one magnet on the other, or it can be said that one magnet sets up a magnetic field in the region around it that affects the other magnet. The magnetic field at any point is a vector. The direction of the magnetic field ( B) at a specified point is the direction that the north end of a compass needle points at that position. Magnetic field lines, analogous to electric field lines, describe the force o...

\( \newcommand\) • • • • • • learning objectives • Express Hall voltage for a a metal containing only one type of charge carriers The Hall effect is the phenomenon in which a voltage difference (called the Hall voltage) is produced across an electrical conductor, transverse to the conductor’s electric current when a magnetic field perpendicular to the conductor’s current is applied. When a magnetic field is present that is not parallel to the motion of moving charges within a conductor, the charges experience the Lorentz force. In the absence of such a field, the charges follow a roughly straight path, occasionally colliding with impurities. In the presence of a magnetic field with a perpendicular component, the paths charges take becomes curved such that they accumulate on one face of the material. On the other face, there is an excess of opposite charge remaining. Thus, an electric potential is created so long as the charge flows. This opposes the magnetic force, eventually to the point of cancelation, resulting in electron flow in a straight path. Hall Effect for Electrons: Initially, the electrons are attracted by the magnetic force and follow the curved arrow. Eventually, when electrons accumulate in excess on the left side and are in deficit on the right, an electric field ξy is created. This force becomes strong enough to cancel out the magnetic force, so future electrons follow a straight (rather than curved) path. For a metal containing only one type of charge car...

\( \newcommand \] Example 10.3.1 A magnetic flux of 6E−5 webers exists in a core whose cross section has dimensions of 1 centimeter by 2 centimeters. Determine the flux density in teslas. First, convert the dimensions to meters to find the area. There are 100 centimeters to the meter. \[A = width \times height \nonumber \] \[A = 0.01 m \times 0.02 m \nonumber \] \[A = 2E-4 m^2 \nonumber \] \[B = \frac \nonumber \] \[B = 0.3T \nonumber \] Ohm's Law for Magnetic Circuits (Hopkinson's or Rowland's Law) There is a common parallel drawn between magnetic circuits and electrical circuits, namely Hopkinson's law (Rowland's law). For electrical circuits, Ohm's law states: \[V = I R \nonumber \] In like manner, for magnetic circuits, we have: \[\boldsymbol \] For other materials, such as sheet steel or cast steel, we shall take another path; namely an empirically derived curve that plots flux density \(B\) against magnetizing force \(H\). Such graphs generically are referred to as “\(BH\) curves”. An example is shown in Figure 10.3.3 . Clearly, this curve is not a nice straight line, or even an obvious, predictable function. The immediately apparent attributes are the initial steep rise which is followed by a flattening of the curve. This flattening corresponds to saturation of the magnetic material. In contrast, a plot for air would reveal a straight line with a very shallow slope. As we shall see, being able to achieve a high flux density for a given magnetizing force will result ...

Most of us have some familiarity with everyday magnetic objects and recognize that there can be forces between them. We understand that magnets have two poles and that depending on the orientation of two magnets there can be attraction (opposite poles) or repulsion (similar poles). We recognize that there is some region extending around a magnet where this happens. The magnetic field describes this region. We require a way to indicate the direction of the field. This is usually done by drawing arrowheads along the lines. Sometimes arrowheads are not drawn and the direction must be indicated in some other way. For historical reasons the convention is to label one region 'north' and another 'south' and draw field lines only from these 'poles'. The field is assumed to follow the lines from north to south. 'N' and 'S' labels are usually placed on the ends of a magnetic field source, although strictly this is arbitrary and there is nothing special about these locations. Very accurate measurement of small magnetic fields has only been practical since the discovery in 1988 of giant magnetoresistance in specially layered materials. This discovery in fundamental physics was quickly applied to the magnetic hard-disk technology used for storing data in computers. This lead to a thousand-fold increase in data storage capacity in just a few years immediately following the implementation of the technology (0.1 to 100 G b i t / i n c h 2 \mathrm G b i t / i n c h 2 G, b, i, t, slash, i, ...

Magnetic Circuit Design Guide 1. Basic calculation formulas 1-1. Total magnetic flux Φ and permeance P The basic calculation formula for magnetic circuits is the same as Ohm's law; namely, when the total magnetic flux is denoted by Φ, the magnetomotive force by F, and the magnetic resistance by R, the relationship among these three elements is expressed by the following formula: This formula shows that the shorter the magnetic path length L and the greater the cross section area A and permeability μ, the greater the permeance P ( i.e. the smaller the magnetic resistance). In addition, permeance Pt for the entire magnetic circuit is expressed by the sum of gap permeance Pg, which is defined as the reciprocal of the magnetic resistance at the gap, and leakage permeance Pf is defined as the reciprocal of the magnetic resistance caused by leakage magnetic flux ( Pt = Pg + Pf ). To grasp the leakage flux for each magnetic path space, total permeance Pt is expressed as a sum of gap permeance Pg and the leakage permeance of each magnetic path space (Pf 1+ Pf 2 + Pf 3+ ....... Pf n). The total magnetomotive force F of the magnetic circuit is given by the magnet used, and its value is the product of the magnetic field strength at the operating point of magnet Hd and magnet length Lm. In addition, the magnetomotive force of gap Fg is the product of gap magnetic flux density Bg and gap length Lg; therefore, Formula (5) can be expanded to the following formula: Total magnetic flux Φt ...

12 Thermodynamics • Introduction • 12.1 Zeroth Law of Thermodynamics: Thermal Equilibrium • 12.2 First law of Thermodynamics: Thermal Energy and Work • 12.3 Second Law of Thermodynamics: Entropy • 12.4 Applications of Thermodynamics: Heat Engines, Heat Pumps, and Refrigerators • Key Terms • Section Summary • Key Equations • 22 The Atom • Introduction • 22.1 The Structure of the Atom • 22.2 Nuclear Forces and Radioactivity • 22.3 Half Life and Radiometric Dating • 22.4 Nuclear Fission and Fusion • 22.5 Medical Applications of Radioactivity: Diagnostic Imaging and Radiation • Key Terms • Section Summary • Key Equations • By the end of this section, you will be able to do the following: • Summarize properties of magnets and describe how some nonmagnetic materials can become magnetized • Describe and interpret drawings of magnetic fields around permanent magnets and current-carrying wires • Calculate the magnitude and direction of magnetic force in a magnetic field and the force on a current-carrying wire in a magnetic field Teacher Support The learning objectives in this section will help your students master the following standards: • (5) The student knows the nature of forces in the physical world. The student is expected to: • (G) investigate and describe the relationship between electric and magnetic fields in applications such as generators, motors, and transformers. In addition, the High School Physics Laboratory Manual addresses content in this section in the lab title...