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Table of Content
20 November 2010 Volume 29 Issue 11
著者文摘
Summarization of the progress in magnetic monopole
. 2010, 29(11): 1-1.
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Since Dirac proposed the concept of magnetic monopole, both the experimental and the theoretical physicists have made great efforts to search for such fantastic particles, but have not found any firm evidence for their existence. Recently, some condensed matter physicists claimed that they had found some convincing evidence of the existence of them in momentum space and spin ice. Furthermore, they interpreted some novel phenomena by the collective behavior of magnetic monopoles. This casts a flash of hope on the difficult road searching for such charming particles. As a supplement of teaching materials, we want to give a summarization of the recently progress in magnetic monopole to provide a whole picture of the magnetic monopoles and to stimulate the interesting of the readers.
A special ＂electromagnetic wave＂ whose propagation velocity can be arbitrary value
. 2010, 29(11): 6-6.
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646
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In this paper, we get a special electromagnetic wave through relativistic transform of a special magnetostatie filed, its propagation velocity can be any value. We point out the essential difference between this special electromagnetic wave and electromagnetic wave in the traditional sense. The difference between electromagnetic wave in the traditional sense and electromagnetic wave is also discussed in a general sense.
Statistical thermodynamics for Bmon gas in one-dimensional harmonic trap
. 2010, 29(11): 9-9.
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767
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A Boson gas in one-dimensional harmonic trap does not exhibit the phase transition, but at low temperature there is a macroscopic condensate in the ground state. At high temperature the internal energy is equal to the product of force and displacement. The number of microstates can not be computed with conventional method, and the correct way of enumeration is presented.
Hylleraas variational calculation for ground-state energy of Helium
. 2010, 29(11): 14-14.
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1079
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361
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By using the Hylleraas-type wave function, the expression for the energy of Helium in the ground state is derived in detail. The variational minimum of ground state energy is obtained by the help of Mathematica. The theoretical value of energy is in agreement with experimental data, and the relative error is less than 0.04‰.This calculation is easy to understand, thus it is very suitable for the teaching purpose.
Research on the movement ot inverted pendulum
. 2010, 29(11): 16-16.
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799
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A simple model of inverted pendulum is proposed and an approximate solution for the movement of the pendulum in the condition of small angle is given by means of combining theoretical analysis with numerical calculation of MATLAB. The result shows that there exists a critical frequency and that the inverted pendulum would fall down when the driving frequency is smaller than the critical frequency while the inverted pendulum may not fall down when the driving frequency is bigger than the critical frequency.
Potential force and gauge symmetry
. 2010, 29(11): 21-21.
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727
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757
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The general properties of potential force are introduced, and the vectorial and scalar potential of inertial force in a general non-inertial frame are presented. The gauge symmetry in this formalism is analyzed, and the comparison with electromagnetism is presented.
A simple method to derive electromagnetic radiation for uniform rotational electric dipoles
. 2010, 29(11): 23-23.
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818
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Positive and negative electric charges will undertake accelerated motion when the electric dipole rotates by its center, so the rotational electric dipole will radiate electromagnetic wave. With the formula of magnetic induction intensity produced by electric charge in motion, an expression of variation magnetic field is derived, which is produced by a uniform rotational electric dipole near itself. With the retarding effect of building electromagnetic field, an expression of electromagnetic radiation in far field is also derived for a uniform rotational electric dipole in the non-relative theory. And then comparisons of the similarities and differences in electromagnetic radiation between the uniform rotational electric dipole and the oscillation electric dipole are carried out.
A simple inferential reasoning method for angular momentum operator
. 2010, 29(11): 26-26.
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1465
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521
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In quantum mechanics textbook, the spherical coordinate forms of both L^2 and L^x are obtained generally by using the Cartesian coordinates, however, the variable substitution calculation is complex. In this paper, the spherical coordinates on the orthogonal basis of coordinate are regarded to variables vectors, and differential nature of the spherical coordinates is used. The derivation for angular momentum operators L^2 and L^x in quantum mechanics is predigested.
Deducing Coulomb potential by Klein-Gordon equation
. 2010, 29(11): 29-29.
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1249
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456
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Quantum electrodynamics tells us that the coulomb potential is produced by exchanging virtual photon between the electric charge, but the most direct proofs are deduced from the coulomb potential in terms of the theory of virtual photon. The Klein-Gordon equation （□^2-m^2） Ф（x, t） = 0） is used to describe the scalar field with the mass m, zero spin and zero charge. The virtual photons can be described by the scalar field with its mass zero, so it satisfies the Klein-Gordon equation： □^2Ф（x, t） = 0. The coulomb potential is also deduced by using the Klein.-Gordon equation.
Discussion about the linear fitting by successive differential method
. 2010, 29(11): 31-31.
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835
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The characteristic of successive differential method is analyzed. It is opened out that which is really a kind of weighted least square method. Various opinions and problems for the method are discussed.
Measurement of coefficient of restitution and gravitational acceleration by using bouncing ball
. 2010, 29(11): 35-35.
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1424
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726
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Re-bouncing collision model between steel ball and glass plate is established, the equations for the measurement of both coefficient of restitution and acceleration due to gravity are obtained. The pulsed acoustic signals with the assistant of acoustic sensor while each collision is acquired. Finally, the measurements of both coefficient of restitution between steel ball and glass plate and free-fall acceleration are performed.
An optimization method for apparatus adjustment of Young＇ s modulus experiment and its implementation plan
. 2010, 29(11): 37-37.
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801
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245
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The adjustment difficulties for the Young＇ s modulus experiment are pointed out, and the difficult reasons are analyzed by using theory into practice. A new simple adjusting method is proposed, i. e. , the insert target method. The problems of aiming at and focusing on are solved effectively. A complete flow chart of the method is given and its implementation plan is also introduced.
An interesting electromagnetic induction pendulum
. 2010, 29(11): 41-41.
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977
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318
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Abstract：An interesting electromagnetic induction pendulum is introduced, here the driving force is the elec-tromagnetic induction magnetic one. It is controlled by the electronic switching circuit when the driving force is emerged. During a full oscillation cycle the pendulum is driven four times by the driving force, so the pendulum can swing all the time, which seems like ＂moving permanent＂. We also describe in detail about how it works and how to make it.
Observation and analysis of the oil droplets sedimentation under the condition of microgravity
. 2010, 29(11): 44-44.
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676
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364
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The gravity effect almost disappears in a micro-gravity environment. The flow characteristics of liquid will be different from itself under the gravity condition. In order to observe the change of the oil droplets, we have built a short-term micro-gravity experimental system, and observed. The image of the oil droplets changing process of the speed and the shape. It is important for the education of the student＇s observation ability, scientific thinking ability through these physics observation experiments.
Other theories on the Ling-long instrument
. 2010, 29(11): 47-47.
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1171
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381
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The Ling-long instrument is an astronomical instrument created by GUO Shou-jing, the famous Chi-nese astronomer fromYuan dynasty,in order to determine the astronomical data he needed to write the ＂Shou-shi calendar＂. There is a wide spectrum of opinions on the Ling-long instrument because there is no real model or blueprint left, and there is little related historical record or description on it too. Scholars from all over the world have various ideas about what kind of instrument the Ling-long really is, among them the armillary theory and the sphereplanetarium theory are the major two. In recent years more people are inclined to agree with -the sphereplanetarium theory, believe that the Ling-long is an imitating sphereplanetarium used in representing shows. Some manufacturers were even ready to produce Ling-long as asphereplanetarium. The author here questioned these two main theories about Ling- long in this essay, and put forward a new suggestion that the Ling-long is actually an astronomical instrument invented by GUO Shou-jing, different with armillary, sphereplanetarium, or any other instrument known by people.
Influence of mass upon the vibration of a spring in the gravity
. 2010, 29(11): 51-51.
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666
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The frequency of an oscillator with a spring of finite mass is derived to satisfy tan tan（√mi/kω）√mi/kω=m1/m2 in the gravity. The force at the fixed point of the vertical spring is measured by a force sensor, its frequency isin agreement with the value obtained from our theoretical analyses.
A discussion for the experiment to measure speed of sound in air
. 2010, 29(11): 55-55.
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1191
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A new explanation of the experiment to measure the speed of sound in the air is proposed. It is shown that the sound pressure is the result of the superposition of infinite reflections of sound waves between the transmitting end and the receiving end. After considering the energy dissipation in the air as well as reflected energy loss and half-wave loss on the two transducer ends, the relationship between the pressure and the displacement of sound waves at the receiving end is obtained. We can reasonably get the law of the sound pressure signal varies with the distance between two transducer ends, which conforms to the concrete experiment.
Explore for the specific heat of the solids
. 2010, 29(11): 61-61.
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754
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468
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In this paper, we introduce the exploring process of the special heat of the solids, especially the Dulong-Petit＇s law and Einstein＇s formula for specific heat, which can be acted as a typical case to promote the creative ability of college students.
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