Joseph Priest

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.

Inexpensive high-precision capacitance measurements and their applications in undergraduate laboratories

An inexpensive system for precision capacitance measurement is presented. The system is appropriate for undergraduate laboratories is based on a newly available capacitance-to-digital integrated circuit that can measure picofarad capacitances to six significant figures. The circuitry software for controlling the integrated circuit with a personal computer via an I2C interface bus are described. Examples of experiments that make use of the circuitry are discussed, including a novel hydrostatic magnetometer that uses precision capacitance measurement to determine the magnetization of a small sample.

Hands-on Magnetic Field Measurements with a GMR Sensor.

Magnetic field sensors based on giant magnetoresistance (GMR) are becoming increasingly useful in laboratory exercises for students taking a beginning course in electromagnetism. We describe three simply conceived, hands-on exercises involving magnetic field measurements that require only a GMR sensor, a 5-V power supply, and a voltmeter having millivolt accuracy.

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.

Meter Resistance: Don't Forget It!

When measuring potential difference or current with an analog meter employing a moving-coil galvanometer, the user has to be sensitive to circuit changes produced by the internal resistance of the meter. Fortunately, analog meters have been largely replaced with digital instruments that ordinarily have negligible effect on the measurements. Nevertheless, there are situations where a digital meter can seriously affect the circuit. We report here such a situation that was embarrassing initially but proved to be instructional in the end.

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.