1. Faraday's Law of Electromagnetic Induction (Faraday's Law): When the change rate of magnetic flux passes through a closed coil, the induced electromotive force will be generated in the coil. Faraday's law of electromagnetic induction can be expressed as: the magnitude of induced electromotive force is directly proportional to the rate of change of magnetic flux. This law is the basic principle to describe electromagnetic induction phenomenon, and it is also the basis of electromagnetic induction generators and transformers.

2. Maxwell-Ampere Law: Maxwell-Ampere Law describes the relationship between the magnetic field generated in a closed loop through a conductor and the current flowing through the loop. According to this law, the magnetic field intensity generated by the current around the conductor is directly proportional to the current intensity, which is related to the shape of the conductor and the direction of the current. This law is the cornerstone of electromagnetic field theory, which reveals the close relationship between current and magnetic field.

3. Maxwell equations: Maxwell equations are the basic equations of electromagnetism, which describe the interaction between electric field and magnetic field as a set of partial differential equations. Maxwell's equations include four equations: Gauss's law (the relationship between electric field flux and charge), Gauss's law of magnetism (the relationship between magnetic field flux and magnetic charge), Faraday's law of electromagnetic induction (the changing magnetic field produces induced electric field) and Ampere's law (the relationship between magnetic field and current). Maxwell's equations unify the theoretical framework of electromagnetism and describe the generation, propagation and interaction of electric and magnetic fields.

The isomorphism of these three laws constitutes the foundation of classical electromagnetism, which is of great significance for understanding and studying electromagnetic phenomena, electromagnetic field and electromagnetic wave.

Origin of three laws of electromagnetism

The three laws of electromagnetism were discovered and sorted out by many scientists who studied independently in different periods. The main contributors are Faraday, Ampere and Maxwell.

Faraday's law of electromagnetic induction was put forward by British physicist michael faraday in 183 1 year. He observed through a series of experiments that when the magnetic flux passing through the closed coil changes, an induced current will be generated in the coil. Faraday summed up this phenomenon as a law, namely Faraday's law of electromagnetic induction.

Maxwell-Ampere Law was put forward by Scottish physicist james clerk maxwell and French physicist Andre-Marie Ampere in the middle of19th century. Maxwell established the equations of electromagnetic field through experiments and theoretical derivation, including a basic law describing the relationship between current and magnetic field. Ampere also independently studied and experimented, and put forward similar laws on the basis of describing the relationship between current and magnetic field. So the contributions of these two scientists are unified into Maxwell-Ampere Law.

Finally, Maxwell put forward Maxwell's equations by integrating and summarizing the electromagnetic research. This set of equations synthesizes Maxwell-Ampere's law, Faraday's law of electromagnetic induction and Gauss's law, and forms a complete theoretical framework of electromagnetism.

The origin of the three laws of electromagnetism is an outstanding contribution made by many scientists in different periods, which is gradually established and improved through experiments and theoretical derivation. These laws have laid the foundation of electromagnetism as an independent discipline, and have had a far-reaching impact on modern science and technology and application.

Application of that three law of electromagnetism

The three laws of electromagnetism are widely used in many fields, including but not limited to the following aspects:

1. power engineering: the law of electromagnetic induction is the basis of generators and transformers in power engineering. Surrounding the conductor in a magnetic field and using Faraday's law of electromagnetic induction, mechanical energy can be converted into electrical energy to realize power generation. Transformer uses the law of electromagnetic induction to realize the transmission and conversion of electric energy.

2. Communication technology: Maxwell equations describe the propagation law of electromagnetic field and provide a theoretical basis for wireless communication technology. Radio, microwave, optical communication and other technologies are all based on the transmission principle of electromagnetic waves, and information is sent and received by modulating and demodulating electromagnetic waves.

3. Imaging technology: The application of Maxwell equations can also explain the light propagation and imaging principle. In cameras, telescopes, microscopes and lasers, the electromagnetic properties of light and Maxwell equations can be used to capture and enlarge images and generate lasers.

4. Electromagnetic compatibility: Electromagnetic interference between electronic equipment and systems is an important engineering challenge and one of the application fields of electromagnetism. Through the analysis of Maxwell equations and the modeling of electromagnetic field, electromagnetic interference can be predicted and controlled, and the interoperability and compatibility of electronic equipment and systems can be improved.

5. Medical imaging: X-ray, MRI and other medical imaging technologies use the interaction between electromagnetic waves and human tissues. Among them, Ampere's law and Maxwell's equations play an important role in describing the interaction between electromagnetic waves and tissues, helping doctors to obtain detailed images of the internal structure of the human body.

Examples of three laws of electromagnetism

1. Question: A straight wire with a length of L passes through a uniform magnetic field with a magnetic field strength of B at a uniform speed V, and the direction of the wire is perpendicular to the direction of the magnetic field. Find the electromotive force generated at both ends of the wire.

Solution: According to Faraday's law of electromagnetic induction, the magnitude of electromotive force caused by both ends of the wire is equal to the absolute value of the product of the length of the wire and the magnetic induction intensity and speed, namely:

E = |L * B * v|

2. Question: The electrified current I of the straight wire is located in the uniform magnetic field B, the length of the wire is L, and the included angle with the magnetic field is θ. Find the potential difference at both ends of the wire.

Answer: According to Maxwell-Ampere Law, the potential difference between the two ends of a wire can be calculated by the following formula:

V = I * L * B * sin(θ)

3. Question: The radius of the circular coil is R, and the uniform magnetic field B is perpendicular to the plane of the coil. How much induced electromotive force will be generated in the coil when the magnetic flux in the coil changes?

Answer: According to Faraday's law of electromagnetic induction, the induced electromotive force generated in the coil is equal to the negative value of the magnetic flux change rate multiplied by the number of turns of the coil. Therefore, the magnitude of the induced electromotive force can be calculated by the following formula:

e =-N * dφ/dt

Here, n represents the number of turns of the coil, and dφ/dt represents the rate of change of magnetic flux.

These examples help to explain how to apply the three laws of electromagnetism to solve problems related to current, magnetic field and electromotive force. In practical application, it is necessary to select appropriate formulas and parameters for calculation according to the actual situation.