Electromagnetism Where the experiment and theory meet
Electromagnetism Where the experiment and theory meet
Family Tree (Blood: Theory) Unification theory Mathematics Chemistry Industry Quantum theory Energy carrier General relativity Optics Special relativity Field theory- → Matter’ s structure Gravitational law Electromagnetism ) Optical communication Radio igh energy Electrics physIcS Electronics Telecommunication Semi-conductor
Electromagnetism Gravitational law High energy physics Electronics Semi-conductor Telecommunication Electrics Radio Optics Optical communication Field theory Family Tree (Blood: Theory) Quantum theory Special relativity General relativity Unification theory Matter’s structure Mathematics Chemistry Energy carrier Industry
Content of my lecture Chapter 1: Field of stationary electric charges Chapter 2: Electric current Chapter 3: Magnetic field Chapter 4: Alternating currents Chapter 5: Maxwell equation Chapter 6: Electromagnetic wave Chapter 7: Foundation of special relativity
Content of my lecture • Chapter 1: Field of stationary electric charges • Chapter 2: Electric current • Chapter 3: Magnetic field • Chapter 4: Alternating currents • Chapter 5: Maxwell equation • Chapter 6: Electromagnetic wave • Chapter 7: Foundation of special relativity
Your lecturer 陈应天 Prof. Chen Ying Tian(Ph. D, Cambridge) yichen@ustc.edu.cn e.3603294 Room 223, Department of Astronomy and Applied Physics
Your lecturer 陈应天 Prof. Chen Ying Tian (Ph.D., Cambridge) ytichen@ustc.edu.cn Tel. 3603294 Room 223, Department of Astronomy and Applied Physics
Necessary Mathematic tools Calculus: Differential Integral include surface integral and volume integral Vector dot product, cross product gradient, divergence, curl and Laplace operator Complex: complex number phase Coordinates transformation Cartesian Cylindrical and Spherical coordinates
Necessary Mathematic tools • Calculus: Differential & Integral include surface integral and volume integral • Vector : dot product, cross product, gradient, divergence, curl and Laplace operator • Complex: complex number & phase • Coordinates transformation :Cartesian, Cylindrical and Spherical coordinates
How to study EM Always think: Positively Always ask: Why? Always do: The drills as more as you can Language: Progressively to transfer Chapter 1 Electric field of stationary charges
How to study E.M. • Always think: Positively! • Always ask: Why? • Always do: The drills as more as you can. • Language: Progressively to transfer Chapter 1 Electric field of stationary charges
1.1 Coulomb law 1.1.1. What is electric charge? This is a question never be answered EC is a quantity derived from electric phenomena 1.1.2. How to define the electric charge? 1 Coulomb. In MKsAunit system, 1C=1A1S Concept: The observatory phenomena is attraction, the measurement quantity is the force, therefore the electric charge is only a definition in the beginning, but lateron 1.1.3. Character of the electric charge Quantum unit of the charge: charge for electron e=1. 6021892X10-19C Conservation of the charge (how to understand the creation of the charge?), Difference with mass(deep discussion 1.1. 4 Torsion experiment and coulomb law Physics starts from torsion pendulum experiments and continues with torsion pendulum experiments The description of Coulomb law: The force between two point charges is proportional to the product of charges and inversely proportional to the square of the distance
1.1 Coulomb Law 1.1.1. What is electric charge? This is a question never be answered. EC is a quantity derived from electric phenomena. 1.1.2. How to define the electric charge? 1 Coulomb . In MKSA unit system, 1C=1A1S Concept: The observatory phenomena is attraction, the measurement quantity is the force, therefore the electric charge is only a definition in the beginning, but later on……. 1.1.3. Character of the electric charge Quantum unit of the charge: charge for electron, e=1.6021892X10-19C Conservation of the charge (how to understand the creation of the charge?); Difference with mass (deep discussion) 1.1.4. Torsion experiment and Coulomb law Physics starts from torsion pendulum experiments and continues with torsion pendulum experiments. The description of Coulomb law: The force between two point charges is proportional to the product of charges and inversely proportional to the square of the distance
Comparison of electric charge and mass Characters Electric ass Charge (gravitational) Property Positive/neg Only ative positive Interaction yes yes Quantization yes no Lozents variation Invariance covariance conservation yes E=mc2 Different definition no Gravitation inertial
Characters Electric Charge Mass (gravitational) Property Positive/neg ative Only positive Interaction yes yes Quantization yes no Lozents variation Invariance covariance conservation yes E=mc2 Different definition no Gravitation al/inertial Comparison of electric charge and mass
Coulombs experiment suspension head fiber
Coulomb’s experiment
The expression of Coulomb law F 1 2Q A兀So Where 8 is the permittivity at vacuum(. 854x10-12farad/m) Discussion 1) Whether the inverse square law is accurate or not To be determined by the experiment 2)Only valid for stationary point charges 3)Vector property for the interaction Comment: a) The limitation of the theory is depending upon the validity of 1) b) The complication of the complete theory of electric field is due to 2 and 3)
The expression of Coulomb law: r r Q Q o a b o F 2 4 1 = Where o is the permittivity at vacuum (8.854x10-12farad/m) Discussion: 1) Whether the inverse square law is accurate or not. To be determined by the experiment 2)Only valid for stationary point charges 3) Vector property for the interaction Comment: a) The limitation of the theory is depending upon the validity of 1) b) The complication of the complete theory of electric field is due to 2) and 3)
