International unit of current
Ampere is the international unit of current, abbreviated as Ampere, with symbol A, which is defined as: two infinite parallel straight lines with a distance of 1 m in vacuum, connected by equal constant current. When the force acting on each wire is 2× 10-7N, the current on each wire is 1 amp.
Current less than ampere can be expressed in milliamperes, microamperes and other units.
1 A = 1000 mA
1 mA = 1000 mA
The commonly used unit on the battery is mAH (milliampere? Hours), for example, 500mAH means that this battery can provide 500mA× 1hr = 1800 coulombs of electrons, that is, it can provide an electrical appliance with a power consumption of 500mA for one hour.
Right hand grip rule
Ampere rule indicates the relationship between current and the direction of magnetic induction line of magnetic field excited by current, which is also called right-handed spiral rule.
(1) Ampere's Law of Linear Current Hold the wire with the right hand, so that the direction pointed by the straight thumb is consistent with the current direction, then the direction pointed by the bent four fingers is the direction around the magnetic induction line.
(2) Ampere rule of circular current makes the bending direction of the four fingers of the right hand consistent with the direction of circular current, so the direction pointed by the straight thumb is the direction of the magnetic induction line on the central axis of circular current.
Ampere's law of linear current also applies to a short period of linear current. Annular current can be regarded as many small linear currents, and for each small linear current, the direction of magnetic induction intensity on the central axis of annular current can be determined by ampere rule of linear current. The direction of the magnetic induction line on the central axis of the annular current is obtained by superposition. Ampere's law of linear current is basic. Ampere rule of annular current can be deduced from ampere rule of linear current. The ampere rule of linear current also applies to the magnetic field generated by linear motion of charge. At this time, the current direction is the same as the positive charge direction, but opposite to the negative charge direction.
Amperometric titration
Electrotitration analysis method using the change of current in electrolytic cell to indicate titration end point. It can be divided into unipolar electrode amperometric titration and bipolar electrode amperometric titration. The current titration with mercury dropping electrode as polarization electrode is called polarographic titration. Amperometric titration using two polarized electrodes is called dead-stop terminal method or biamperometric titration.
ampere's force
The force of magnetic field on current. The acting force of current element Idl in external magnetic field B is DF = Idl× B, and the direction of ampere force is determined by dl and B according to the right-hand helix law, and the magnitude of ampere force is DF = Bidlsina, where A is the included angle between dl and B. The magnetic field force on any current-carrying conductor is the vector sum of each current element force. Ampere force formula is a part of ampere's law about the interaction of current elements. Ampere force is the macroscopic expression of Lorentz force of magnetic field on moving charge.
1, the influence of magnetic field on current
A bar magnet can attract a small iron block within a certain distance, while a huge electromagnet can attract a steel block weighing several tons, indicating the strength of the magnetic field. How to express the strength of magnetic field? We study the strength of the magnetic field by using the ampere force of the magnetic field acting on the current.
2. What are the factors that determine Ampere?
(1) is related to current.
The force exerted by the magnetic field on the charged straight wire perpendicular to the magnetic field is related to the current in the wire, which is large and powerful; Small current, small force.
(2) It is related to the length of the electrified wire in the magnetic field.
The magnitude of the magnetic field acting on the charged straight wire perpendicular to the magnetic field direction is related to the length of the charged wire in the magnetic field. The wire is long and the force is large. The wire is short and the strength is small.
(3) It is related to the direction of the conductor in the magnetic field.
Keep the current and length of the electrified wire unchanged, and change the included angle between the wire and the magnetic field direction. When the included angle is 0, the wire will not move, that is, when the current is parallel to the magnetic field direction, it is not affected by ampere force. When the included angle increases to 90, the swing angle of the conductor increases continuously, that is, when the current is perpendicular to the magnetic field direction, the ampere force is the largest; When it is not parallel or perpendicular, the ampere force is between 0 and the maximum.
3. Magnetic induction intensity
L represents the length of the live wire, I represents the current, and the directions of the current and the magnetic field remain vertical, and the ampere force on the live wire is FIL.
This ratio is represented by b, and the physical meaning of b = f/il.b is: the live wire is placed vertically at the same position of the magnetic field, and the value of b remains unchanged; If the position of the live wire changes, the value of b will also change accordingly. It shows that the value of B is determined by the position of the magnetic field itself. For wires with the same current and length, the ampere force F is also large when placed at the position with large B value, indicating that the magnetic field is strong. The ampere force f at the position with small B value is also small, indicating that the magnetic field is weak. Therefore, we can use the ratio B=F/IL to express the strength of the magnetic field, which is called the magnetic induction strength.
Definition: magnetic induction intensity B=F/IL.
Unit: Tesla, with symbol T.
1T = 1N/ am
The magnetic induction line can also directly reflect the strength and direction of the magnetic field. The denser the magnetic induction lines, the stronger the magnetic induction intensity. If the magnetic induction intensity and direction are the same everywhere, it is called a uniform magnetic field. According to the characteristics of uniform magnetic field, please draw the spatial distribution of magnetic induction lines of uniform magnetic field.
In the inhomogeneous magnetic field, when measuring the magnetic induction intensity with B=F/IL, the length L of the wire should be very short, and the current is approximately in the homogeneous magnetic field.
4, Ampere force size and direction
According to the definition of magnetic induction intensity, it can be concluded that the ampere force on the live wire when it is placed perpendicular to the magnetic field direction is B=F/IL.
Ampere circuit law
Ampere's law of loop: the line integral of the magnetic induction intensity vector along any closed path is equal to the algebraic sum of the magnetic permeability of vacuum multiplied by the current passing through the area surrounded by the closed path.
∮L B*dl =μ0*∑I (L is subscript, B and DL are vectors)
The current and the winding direction of the loop constitute a positive value of the right-handed spiral relationship, otherwise it takes a negative value.
Ampere prize
Prize awarded by the Paris Academy of Sciences. Electricite de France was founded in 1975 to commemorate the 200th birthday of physicist Ampere (1775- 1836). It awards prizes once a year to one or more French scientists who have made outstanding achievements in pure mathematics, applied mathematics or physics.
Brief introduction of ampere
The French physicist Andre-Marie André-Marie Ampère (1775-1836) has made outstanding achievements in the research of electromagnetic action, and also made contributions in mathematics and chemistry. Ampere, the international unit of current, is named after its surname.
1775 65438+/kloc-0 was born in a wealthy family in Lyon on October 22nd, and died in Marseille on June 1836. From 65438 to 0802, he was a professor of physics and chemistry at Bourjean-Bryce Central School. 1808 was appointed as the Governor of Imperial University of France, and has been in this position ever since; 18 14 was elected as a member of the Department of Mathematics of Imperial College London; 18 19 presided over the philosophy lecture of the University of Paris; 1824 professor of experimental physics, French college.
The most important achievement of Ampere is the study of electromagnetic action from 1820 to 1827. 1820 In July, after H.C. Oster published a paper on the magnetic effect of current, Ampere reported his experimental results: the electrified coil is similar to a magnet; On September 25, he reported that two current-carrying wires interact with each other, and parallel currents in the same direction attract each other, while parallel currents in the opposite direction repel each other; The attraction and repulsion between the two coils are also discussed. Through a series of classic and simple experiments, he realized that magnetism is produced by moving electricity. He used this view to explain the causes of geomagnetism and material magnetism. He put forward the hypothesis of molecular current: the current flows from one end of the molecule and is injected from the other end through the space around the molecule; The current of non-magnetized molecules is evenly and symmetrically distributed and does not show magnetism to the outside; When influenced by an external magnet or current, the symmetry is destroyed, showing macroscopic magnetism, and then the molecules are magnetized. Today, with the high development of science, Ampere's molecular current hypothesis has real content and becomes an important basis for understanding the magnetism of matter. In order to further illustrate the interaction between currents, during the period of 182 1 ~ 1825, Ampere made four exquisite experiments on the interaction between currents, and based on these four experiments, the interaction force formula between two current elements was deduced. 1827, Ampere incorporated his research on electromagnetic phenomena into the book Mathematical Theory of Electrodynamics Phenomenon, which is an important classical treatise in the history of electromagnetism and has a far-reaching influence on the future development of electromagnetism. In order to commemorate the outstanding contribution of ampere in electricity, the unit ampere of current is named after his surname.
He studied probability theory and integral partial differential equations, which showed his special talent in mathematics. He also did chemical research, and David realized the elements chlorine and iodine almost at the same time; Three years later than avogadro, avogadro's law was deduced.
Introduction to English
André-Marie Ampère (1775 1 20th of the month-10/6th of the month 1836), a French physicist, is recognized as one of the main discoverers of electromagnetism. Ampere, the international unit of electric current, is named after him.
Contribution to physics and further research
On the recommendation of Jean batiste Joseph delambre, he was appointed in Lyon, and later (1804) he was appointed as a professor of mathematics at the Paris Institute of Technology (1809). Here, he continued to tirelessly engage in scientific research and all kinds of research. 18 14 was accepted as a member of the society.
Ampère's reputation mainly lies in his contribution to science, establishing the relationship between electricity and magnetism, and developing electromagnetism, or electrodynamics as he called it. On September 20th, he heard of H.C.? Sterd found that the magnetic needle was acted by current. Just one week later, on September 18, he submitted a paper to the college, which contained a more complete exposition of this phenomenon and similar phenomena.
Ampere's life
When I was a child, Ampere had a strong memory and outstanding mathematical ability. His father was deeply influenced by Rousseau's (17 12- 1778) educational thought, and decided to let Ampere teach himself and often took him to the library to read books. Ampere taught himself the history of science, encyclopedias and other works. He was most fascinated by mathematics, and published his first mathematical paper at the age of 13, discussing the spiral line. 1799 ampere teaches mathematics in a middle school in Lyon. 1802 In February, Ampere left Lyon to teach physics and chemistry at Fort College. In April, he published an article about the mathematical theory of gambling, which revealed the excellent mathematical foundation and attracted the attention of the society. Later, he applied for a position in the French public school founded by Napoleon. 1808, Ampere was a governor of Imperial University of France, 1809, he was a professor of mathematics at the University of Paris. 18 14 was elected as an academician of the French Academy of Sciences. 1824 professor of experimental physics, French college. 1827 was elected as a member of the Royal Society of London. He is also an academician of the Academy of Sciences such as Berlin and Stockholm.
Ampere's main contribution to physics is that he has made important discoveries on the basic principles of electromagnetism, such as Ampere's law, Ampere's rule and molecular countercurrent. 1July 2, 8201day, Danish physicist Oster discovered the magnetic effect of current. French physicists have long believed in Coulomb's creed that electricity and magnetism have nothing to do with each other. This great discovery greatly shocked them, and French physicists represented by arago (1786- 1853) and Ampere responded quickly. At the end of August, arago heard the news of Oster's success in Switzerland and immediately rushed back to France. On September 1 1, he reported the details of Oster's experiment to the French Academy of Sciences. After listening to the report, Ann repeated Oster's experiment the next day, and reported the first paper to the French Academy of Sciences on September 18, proposing that the relationship between the rotation direction, direction and current direction of the magnetic needle should obey the right-hand rule, which was later named Ampere's rule. On September 25th, Ampere reported the second paper to the Academy of Sciences, proposing that two parallel current-carrying wires with the same current direction attract each other and two parallel current-carrying wires with opposite current directions repel each other. 1On October 9th, the third paper was reported, and the interaction between various shapes of bent current-carrying wires was expounded. Later, Ampere did many experiments. In 1826, he summed up the law of force between current elements with high mathematical skills and described the relationship between the interaction between two current elements and the size, spacing and relative orientation of the two current elements. Later, people called this law ampere's law. 1February 4th, Ampere reported this achievement to the Academy of Sciences. Ampere is not satisfied with the results of these experimental studies. 182 1 year 1 month, he put forward the famous molecular current hypothesis that the circulation of each molecule forms ten small magnets, which is the reason why objects have macroscopic magnetism. Ampere also compared the names of statics and dynamics. He was the first to call the theory of electrodynamics "electrodynamics", and published "Observations on Electrodynamics" in' 1822 and "Electrodynamics Theory of Moths" in' 1827. In addition, Ampere found that the magnetism of the current flowing in the coil was similar to that of a magnet. He invented the first solenoid, and on this basis, he invented a galvanometer to detect and measure the current.
Ampere's research also involves philosophy, chemistry and other fields, and even studies complex problems in plant taxonomy.
1836, Ampere went out to inspect the work as a university inspector. Unfortunately, he contracted acute pneumonia on the way and died in Marseille on June 10 at the age of 6 1. In order to commemorate Ampere, later generations named the unit of current intensity after him, referred to as "An".
Scientific achievements
The most important achievement of Ampere is the study of electromagnetic action from 1820 to 1827.
(1) discovered ampere's law.
Oster's experiment of discovering the magnetic effect of current attracted Ampere's attention, which greatly impacted his long-standing belief in Coulomb's creed that electricity has nothing to do with magnetism. He concentrated all his energy on this research. Two weeks later, he presented a report on the relationship between the rotation direction of the magnetic needle and the current direction and the ruler from the right hand. Later, this law was named Ampere's Law.
(2) Discover the interaction law of current.
Then he proposed that two parallel current-carrying wires with the same current direction attract each other, and two parallel current-carrying wires with opposite current directions repel each other. The attraction and repulsion between the two coils are also discussed.
③ The galvanometer was invented.
Ampere also found that the magnetism of the current flowing in the coil was similar to that of a magnet, and made the first solenoid. On this basis, he invented a galvanometer to detect and measure current.
④ Propose the molecular flow hypothesis.
He explained the origin of geomagnetism and the magnetism of matter according to the viewpoint that magnetism is produced by moving charges. The famous molecular flow hypothesis was put forward. Ampere thinks that there is a kind of annular current-molecular current inside the molecules that make up the magnet. Because of the molecular current, each magnetic molecule becomes a small magnet, and both sides are equivalent to two magnetic poles. Usually, the molecular current orientation of magnet molecules is disordered, and the magnetic fields generated by them cancel each other, so they are not magnetic to the outside world. When the external magnetic field acts, the orientations of molecular currents are almost the same, and the adjacent currents between molecules cancel each other, but the surface parts do not cancel each other, and their effects show macroscopic magnetism. Ampere's molecular current hypothesis could not be confirmed when little was known about the material structure at that time, which contained quite a few speculative components; It has been learned today that matter is made up of molecules, and molecules are made up of atoms, in which electrons move around the nucleus. Ampere's molecular current hypothesis has real content and becomes an important basis for understanding the magnetism of matter.
⑤ Summarized the law of action between current elements-Ampere's law.
Ampere made four exquisite experiments on current interaction, summed up the law of force between current elements with superb mathematical skills, and described the relationship between the interaction between two current elements and the size, spacing and relative orientation of two current elements. Later, people called this law ampere's law. Ampere was the first to call the theory of electrodynamics "electrodynamics". 1827, Ampere integrated his research on electromagnetic phenomena into the book Mathematical Theory of Electrodynamics. This is an important classic work in the history of electromagnetism. In order to commemorate his outstanding contribution to electromagnetism, the unit of current "ampere" was named after his surname.
He also made many contributions in mathematics and chemistry. He studied probability theory and integral partial differential equations; Almost at the same time as David H, he knew the elements chlorine and iodine, derived avogadro's law, demonstrated the relationship between volume and pressure at constant temperature, and tried to find the classification and arrangement order of various elements.
anecdote
1. Pocket watch becomes pebble
Ampere was absorbed in thinking about scientific problems. It is said that once, Ampei was walking slowly to the school where he taught, thinking about an electrical problem while walking. When crossing the Seine, he picked up a pebble and put it in his pocket. After a while, he took it out of his pocket and threw it into the river. When he got to school, he walked into the classroom and was used to looking at the time in his pocket watch, but he took out a pebble. It turns out that the pocket watch has been thrown into the Seine.
2. The carriage is a blackboard.
Another time, Ampere was walking in the street, and he came up with a formula for electrical problems. He is worried that there is no place to operate. Suddenly, he saw a blackboard in front of him, so he took out the chalk he carried with him and wrote on it. The blackboard turned out to be the back of a carriage. The carriage moved, and he followed, writing while walking; As the carriage became faster and faster, he began to run, bent on completing his deduction, and didn't stop until he really couldn't catch up with the carriage. Ampere's abnormal behavior made people in the street laugh their heads off.
3. Newton in Electricity
Ampere integrated his research results into the book Mathematical Theory of Electrodynamics Phenomenon, which became an important classic work in the history of electromagnetism. Maxwell praised Ampere's work as "one of the most brilliant achievements in science" and called Ampere "Newton in electricity".
Ampere was also the first person to develop the technology of measuring electricity. He made an instrument for measuring current with an automatic rotating magnetic needle, which was later improved into a galvanometer.
Ampere only worked in physics for a short time in his life, but he was able to discuss the magnetic effect of charged wires with unique and thorough analysis, so we called him a pioneer of electrodynamics, and he deserved it.
International unit of current
Ampere is the international unit of current, abbreviated as Ampere, with symbol A, which is defined as: two infinite parallel straight lines with a distance of 1 m in vacuum, connected by equal constant current. When the force acting on each wire is 2× 10-7N, the current on each wire is 1 amp.
Current less than ampere can be expressed in milliamperes, microamperes and other units.
1 A = 1000 mA
1 mA = 1000 mA
The commonly used unit on the battery is mAH (milliampere? Hours), for example, 500mAH means that this battery can provide 500mA× 1hr = 1800 coulombs of electrons, that is, it can provide an electrical appliance with a power consumption of 500mA for one hour.
Right hand grip rule
Ampere rule indicates the relationship between current and the direction of magnetic induction line of magnetic field excited by current, which is also called right-handed spiral rule.
(1) Ampere's Law of Linear Current Hold the wire with the right hand, so that the direction pointed by the straight thumb is consistent with the current direction, then the direction pointed by the bent four fingers is the direction around the magnetic induction line.
(2) Ampere rule of circular current makes the bending direction of the four fingers of the right hand consistent with the direction of circular current, so the direction pointed by the straight thumb is the direction of the magnetic induction line on the central axis of circular current.
Ampere's law of linear current also applies to a short period of linear current. Annular current can be regarded as many small linear currents, and for each small linear current, the direction of magnetic induction intensity on the central axis of annular current can be determined by ampere rule of linear current. The direction of the magnetic induction line on the central axis of the annular current is obtained by superposition. Ampere's law of linear current is basic. Ampere rule of annular current can be deduced from ampere rule of linear current. The ampere rule of linear current also applies to the magnetic field generated by linear motion of charge. At this time, the current direction is the same as the positive charge direction, but opposite to the negative charge direction.
Amperometric titration
Electrotitration analysis method using the change of current in electrolytic cell to indicate titration end point. It can be divided into unipolar electrode amperometric titration and bipolar electrode amperometric titration. The current titration with mercury dropping electrode as polarization electrode is called polarographic titration. Amperometric titration using two polarized electrodes is called dead-stop terminal method or biamperometric titration.
ampere's force
The force of magnetic field on current. The acting force of current element Idl in external magnetic field B is DF = Idl× B, and the direction of ampere force is determined by dl and B according to the right-hand helix law, and the magnitude of ampere force is DF = Bidlsina, where A is the included angle between dl and B. The magnetic field force on any current-carrying conductor is the vector sum of each current element force. Ampere force formula is a part of ampere's law about the interaction of current elements. Ampere force is the macroscopic expression of Lorentz force of magnetic field on moving charge.
1, the influence of magnetic field on current
A bar magnet can attract a small iron block within a certain distance, while a huge electromagnet can attract a steel block weighing several tons, indicating the strength of the magnetic field. How to express the strength of magnetic field? We study the strength of the magnetic field by using the ampere force of the magnetic field acting on the current.
2. What are the factors that determine Ampere?
(1) is related to current.
The force exerted by the magnetic field on the charged straight wire perpendicular to the magnetic field is related to the current in the wire, which is large and strong; Small current, small force.
(2) It is related to the length of the electrified wire in the magnetic field.
The magnitude of the magnetic field acting on the charged straight wire perpendicular to the magnetic field direction is related to the length of the charged wire in the magnetic field. The wire is long and the force is large. The wire is short and the strength is small.
(3) It is related to the direction of the conductor in the magnetic field.
Keep the current and length of the electrified wire unchanged, and change the included angle between the wire and the magnetic field direction. When the included angle is 0, the wire will not move, that is, when the current is parallel to the magnetic field direction, it is not affected by ampere force. When the included angle increases to 90, the swing angle of the conductor increases continuously, that is, when the current is perpendicular to the magnetic field direction, the ampere force is the largest; When it is not parallel or perpendicular, the ampere force is between 0 and the maximum.
3. Magnetic induction intensity
L represents the length of the live wire, I represents the current, and the directions of the current and the magnetic field remain vertical, and the ampere force on the live wire is FIL.
This ratio is represented by b, and the physical meaning of b = f/il.b is: the live wire is placed vertically at the same position of the magnetic field, and the value of b remains unchanged; If the position of the live wire changes, the value of b will also change accordingly. It shows that the value of B is determined by the position of the magnetic field itself. For wires with the same current and length, the ampere force F is also large when placed at the position with large B value, indicating that the magnetic field is strong. The ampere force f at the position with small B value is also small, indicating that the magnetic field is weak. Therefore, we can use the ratio B=F/IL to express the strength of the magnetic field, which is called the magnetic induction strength.
Definition: magnetic induction intensity B=F/IL.
Unit: Tesla, with symbol T.
1T = 1N/ am
The magnetic induction line can also directly reflect the strength and direction of the magnetic field. The denser the magnetic induction lines, the stronger the magnetic induction intensity. If the magnetic induction intensity and direction are the same everywhere, it is called a uniform magnetic field. According to the characteristics of uniform magnetic field, please draw the spatial distribution of magnetic induction lines of uniform magnetic field.
In the inhomogeneous magnetic field, when measuring the magnetic induction intensity with B=F/IL, the length L of the wire should be very short, and the current is approximately in the homogeneous magnetic field.
4, Ampere force size and direction
According to the definition of magnetic induction intensity, it can be concluded that the ampere force on the live wire when it is placed perpendicular to the magnetic field direction is B=F/IL.
Ampere circuit law
Ampere's law of loop: the line integral of the magnetic induction intensity vector along any closed path is equal to the algebraic sum of the magnetic permeability of vacuum multiplied by the current passing through the area surrounded by the closed path.
∮L B*dl =μ0*∑I (L is subscript, B and DL are vectors)
The current and the winding direction of the loop constitute a positive value of the right-handed spiral relationship, otherwise it takes a negative value.
Ampere prize
Prize awarded by the Paris Academy of Sciences. Electricite de France was founded in 1975 to commemorate the 200th birthday of physicist Ampere (1775- 1836). It awards prizes once a year to one or more French scientists who have made outstanding achievements in pure mathematics, applied mathematics or physics.