Donald C. Kelly

MAGNETIC PROPERTIES OF MATTER

This chapter discusses the magnetic properties of matter by making qualitative observations of the behavior of various materials placed in a non-uniform magnetic field. These observations allow one to classify the magnetic materials as diamagnetic, paramagnetic, and ferromagnetic. Measurements of the magnetic dipole moment of a wide variety of materials lead to a quantitative classification of magnetic materials in terms of the magnetic susceptibility. Diamagnetism is the result of magnetically induced atomic dipoles. Paramagnetism is due to orientation of weakly interacting magnetic moments associated with electron magnetic moments and circulating electron currents. Ferromagnetism results from a very strong mutual interaction between magnetic moments. This interaction produces nearly perfect magnetic alignment in regions called magnetic domains. Permanent ferromagnets are produced by the alignment of magnetic domains. The chapter also presents an overview of the earths magnetic field, which is similar to that of an elementary magnetic dipole. The earths magnetic field is believed to be caused by circulating interior electric currents.

CAPACITANCE AND CAPACITORS

Publisher Summary No single electronic component plays a more important role in the electronic age than a charge-storing mechanism called capacitor. Capacitors help to understand the energy aspects of electric fields and the properties of insulators. They are used to establish electric fields, to minimize voltage variations in electronic power supplies, to increase the efficiency of electric power transmission, and to provide energy for certain types of nuclear fusion energy devices and nuclear particle accelerators. Capacitors are used in the electronic circuits that detect and generate electromagnetic waves and as the components of electronic circuits used to measure time. This chapter discusses a type of capacitor that consists of two conductors separated by an insulator. It presents the way in which capacitor can accumulate and store a net amount of electric charge. The chapter introduces capacitance as a quantitative measure of the charge-storing ability. It discusses the equivalent capacitance of series and of parallel combinations of capacitors. It presents the energy aspects of capacitors and discusses the role of the insulator in a capacitor.

TEMPERATURE AND HEAT

This chapter provides an account of temperature and heat. Temperature is a fundamental property that determines whether or not systems are in mutual thermal equilibrium. Mutual thermal equilibrium defines temperature equality. Thermodynamics deals with the properties of bulk matter under conditions where the effects of heat and temperature are significant. The zeroth law formalizes an important experimental fact that thermal equilibrium between two systems demands the equality of one property—the property called temperature. The first law recognizes heat as a form of energy and states that energy is conserved in all processes. The chapter develops operational definitions of temperature and heat. In a thermodynamic process, one or more of the thermodynamic variables change. A quasi-static process is one in which the surroundings and thermodynamic variables of the system change so slowly that the process can be viewed as one in which the system passes through a succession of equilibrium states. Geometrically, a quasi-static process can be represented by a path that joins the initial and final equilibrium states by a succession of intermediate equilibrium states.

MOTION IN A PLANE

This chapter develops the theory of linear motion with constant acceleration, or uniformly accelerated motion to illustrate the concepts of velocity and acceleration, and to show how equations are used to describe motion. The principle of superposition as it applies to the vector quantities position, velocity, and acceleration is considered in the chapter. It also discusses the theory of uniformly accelerated motion to motion in a plane. Displacement, velocity, and acceleration all satisfy the principle of superposition. This principle is used to consider the horizontal and vertical parts of projectile motion. The theory of linear motion is applied, with only minor adjustments in notation, to problems involving motion in a plane. In uniform circular motion, the speed of a particle is constant, but the direction of the velocity vector changes with time. These changes are associated with acceleration—called centripetal—directed radially toward the center of rotation. If the speed of a particle in circular motion changes, another component of the acceleration—called tangential—is directed tangent to the path of the particle.

CONSERVATION OF LINEAR MOMENTUM

This chapter discusses the principles of conservation of linear momentum. The linear momentum of a particle is the product of that particles velocity and mass. Linear momentum, like energy, is conserved under certain conditions. The chapter introduces the concept of linear impulse and uses it to reformulate Newtons second law, to provide a basis for the law of conservation of linear momentum. In the new formulation, the net linear impulse represents the influence of the environment on the particle. Linear impulse is the second of three physical quantities that represent the influence of the environment on particle motion. Each of these three quantities—work, linear impulse, and torque—is defined in terms of force, and each leads to a conservation law. The chapter discusses how the linear momentum of a particle changes in response to an external linear impulse. For linear momentum to be conserved, the net external linear impulse must vanish. This idea is extended to interactions involving two particles, and the vector law is illustrated with several examples.

QUANTUM PHYSICS, LASERS, AND SQUIDS

This chapter provides an overview of quantum physics. Quantum physics has given birth to the quantum engineering fields of quantum optics and squids. Planck adopted a quantum viewpoint to explain the spectrum of blackbody radiation. Einstein treated light as a particle to develop a theory of the photoelectric effect. From the analysis of α-particle scatter, Rutherford concluded that the positive charge and most of the mass of an atom were concentrated in a small central region, called the nucleus. Bohr conceived a quantum theory for the hydrogen atom. The shortcomings and successes of the Bohr theory spurred the development of a new quantum theory. De Broglie postulated relationships between the wave and particle attributes. Davisson and Germer confirmed de Broglies wave theory by demonstrating experimentally that electrons can show interference. Schrodinger developed an equation that describes the de Broglie waves. Quantization emerged from the solutions of Schrodingers equation. Most noteworthy in the area of quantum optics is the laser, a device that produces a highly directional and intense beam of coherent light. In addition, the phenomenon of superconductivity has made possible the development of squids, a class of measuring instruments based on the quantum interference of super-currents.

THERMAL PROPERTIES OF MATTER

This chapter presents the thermal expansion of solids and liquids. It also discusses the changes of phase, which include melting and boiling. Additionally, this chapter develops the concept of an ideal gas. The ideal gas is a generalized model of a gas that incorporates the basic properties common to all real gases. This model offers both practical and conceptual advantages. The engineer who wants a rough idea how a temperature change will affect the pressure of a particular gas can rely on the ideal gas model. By using the ideal gas model, the engineer can avoid minor details. The ideal gas model not only makes calculations simpler but also makes it easier to grasp certain thermodynamic concepts. The ideal gas plays the same role in thermodynamics as does the “point mass” or “particle” in mechanics. It can be used to illustrate the principles of thermodynamics at an intuitive level.

MANY-PARTICLE SYSTEMS

This chapter presents the method in which Newtons laws of motion and the conservation laws for energy and linear momentum are applied to one- and two-particle systems. To extend that treatment on a particle-by-particle basis to a system of many particles, one would require the use of a large electronic computer; however, when the center-of-mass concept is used to describe the dynamic behavior of a many-particle system, the description is no more complex than that of a single particle. In the chapter, the center-of-mass concept is developed and applied to several systems. The chapter introduces the center-of-momentum, which is a generalization of the center-of-mass concept. In many situations, it is legitimate and desirable to ignore the rotation and internal motions of a system. In those situations, the center-of-mass concept greatly simplifies the analysis of the motion because the many-particle system can be treated as a single particle located at the systems center of mass.

NUCLEAR STRUCTURE AND NUCLEAR TECHNOLOGY

This chapter introduces the basic neutron–proton model of the nucleus upon which modern nuclear models are based. It discusses the role that this model plays in 20th century physics and technology. The nucleus of the atom is a bound system of neutrons and protons that, collectively, are called nucleons. The binding energy of a nucleus is the minimum energy that must be added to a nucleus to separate it into its constituent neutrons and protons. As the number of protons in stable nuclei increases, the neutron number gets progressively larger than the proton number. In all nuclear reactions, the conservation laws involving energy, linear momentum, angular momentum, and charge apply. In a spontaneous disintegration of a nucleus, rest mass energy considerations require that the combined masses of the disintegration products be less than the mass of the disintegrating nucleus. The rest mass energy is transformed into kinetic energy, which is shared by the reaction products. Like the energies associated with an atom, the energies of a nucleus are discrete. A nucleus may absorb energy and make a transition to a state of higher energy. However, energy might be released and it might move to a lower energy state.

MOTION OF A RIGID BODY

This chapter introduces rotational forms for work and impulse. These forms are used as a basis for developing a rotational treatment of energy and power, and for dealing with impact situations that involve rotation. When a rigid body possesses linear and rotational motion, the description of its motion can be simplified by choosing the origin to be in one of two special locations. The first is a point in the body that is fixed, even if only for an instant, and the second is the center of mass. The chapter also introduces precession, which is one of the most striking types of rigid body rotational motion. Precession involves a spin axis that varies in direction, and is found in everything that spins—such as, atoms, neutron stars, planets, and toy tops. However, in a pure rotation, points of the rigid body that are on the axis of rotation do not move. The chapter illustrates the comparison of pure rotational motion with rolling-without-slipping motion.