"Magnetism Generates Electricity" Electricity and Magnetism PPT

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"Magnetism Generates Electricity" Electricity and Magnetism PPT

Part One: Knowledge Management

1. Electromagnetic induction

Phenomenon: When a part of a conductor in a closed circuit moves to cut magnetic field lines in a magnetic field, a current (induced current) is generated in the conductor. This phenomenon is called electromagnetic induction. The current produced is called induced current.

The conditions for generating induced current: (1) closed circuit; (2) the closed part of the conductor moves to cut the magnetic field lines.

The direction of the induced current: It is related to the direction of the magnetic field and the direction of the movement of the conductor cutting the magnetic field lines.

Energy conversion: mechanical energy → electrical energy.

Note: If there is a change in the direction of the magnetic field and the direction in which the conductor cuts the magnetic field lines, the direction of the induced current will also change. If the above directions change at the same time, the direction of the induced current will not change.

2. dynamo

Structure: Composed of coils, magnetic poles, copper rings and brushes.

Working principle: It works using the phenomenon of electromagnetic induction.

Energy conversion: mechanical energy → electrical energy.

Note: The actual generator structure is different. The coil does not move and the magnetic poles (in order to obtain a stronger magnetic field, electromagnets are often used) rotate. This kind of generator is called a rotating magnetic pole generator.

3. AC and DC

Definition: A current that does not change in size and direction is called direct current; a current that changes periodically in size and direction is called alternating current.

Note: The alternating current used for production and daily life in my country has a cycle of 0.02 s, a frequency of 50 Hz, and the direction of the current changes 100 times per second.

Magnetism generates electricity PPT, the second part of the content: classification and exploration

One type: electromagnetic induction phenomenon

[2019•Shandong Linyi]As shown in the figure, when the metal rod ab moves to the right, the pointer of the sensitive galvanometer will swing to the right. The direction of the current generated in the following four situations is the same as in the figure (C)

[Analysis] When the metal rod ab moves to the right, it cuts the magnetic field lines in the magnetic field. The pointer of the sensitive galvanometer will swing to the right, indicating that there is current in the circuit. This phenomenon is called electromagnetic induction, and the current generated is called induction. Current; conditions for generating induced current: a part of a conductor in a closed circuit moves in a magnetic field to cut the magnetic field lines. From comparison, it can be seen that Figure D does not cut the magnetic field lines, so D cannot produce induced current; the direction of the induced current is related to the direction of the magnetic field and the movement direction of the conductor. In the picture in question, the direction of the magnetic field lines is from top to bottom, and the conductor is directed towards Right movement, in order to produce the same current direction as in the question picture, the direction of the magnetic field lines and the movement direction of the conductor must be changed at the same time. By comparison, it can be seen that the direction of the current generated in Figure C is the same as that in the question picture. So choose C.

[Summary] To determine whether an induced current is generated, three key words should be paid attention to: "closed circuit", "part of the conductor" and "cutting magnetic field line movement". Only when these three conditions are met at the same time can an induced current be generated.

Type 2 Application of electromagnetic induction

[2018•Guangxi Hezhou]As shown in the figure, the following figures work using the principle of electromagnetic induction (C)

[Analysis] Oersted's experiment shows that there is a magnetic field around the energized conductor, which is the magnetic effect of the current, so A is wrong; the speaker is made using the principle that the energized conductor is forced to move in the magnetic field, so B is wrong; dynamic microphone When working, the sound of people talking makes the coil move in the magnetic field, and the result is the generation of electric current. The principle of electromagnetic induction is used, so C is correct; the electromagnet is made by using the magnetic effect of electric current, so D is wrong. So choose C.

Type 3: Generator and electric motor

[2018•Bayannur, Inner Mongolia] After long-term research, scientists have discovered that electricity and magnetism are closely related. Two important scientific investigations are shown in Figures A and B. The following are about these two sciences The correct statement of inquiry is (B)

A. The A-tu experiment explores the effect of magnetic fields on current-carrying wires

B． The principle revealed in the experiment in Figure B can be made into an electric motor

C. As long as the conductor bar a in Figure A moves, a current will be generated in the circuit.

D. In Figure B, if only the poles of the magnet are reversed, the direction of movement of conductor rod ab will not change.

[Analysis] In Figure A, when ab moves to cut the magnetic field lines, a current will be generated in the circuit. Therefore, this experiment explores the phenomenon of electromagnetic induction, so A is wrong. The experiment in Figure B is that the energized wire is affected by the magnetic field force in the magnetic field. In the experiment, a motor was made based on this principle, so B is correct; in Figure A, only when ab moves to cut the magnetic field lines, current will be generated in the circuit, so C is wrong; there are two factors that affect the direction of the conductor's movement: direction and the direction of the magnetic field. When the poles of the magnet in Figure B are reversed, the direction of motion of the conductor will change, so D is wrong. So choose B.

Magnetism generates electricity PPT, the third part: evaluation in class

1. [2018•Dalian, Liaoning]The principle of generator is (　A　)

A. Electromagnetic induction

B． A current-carrying conductor experiences forces in a magnetic field

C. magnetic effect of electric current

D. heating effect of electric current

2. [2018•Wuzhou, Guangxi Province An induced current will be generated, and the information on the magnetic strip can be read. The working principle of the following equipment is the same as that of the card reader for reading information (B)

A. Electromagnet b. dynamo

C. Electric motor D. Electromagnetic relay

[Analysis] As can be seen from the meaning of the question, the working principle of the card swiping machine is the phenomenon of electromagnetic induction. Electromagnets are made by using the magnetic effect of electric current, so A is wrong; generators are made by using the principle of electromagnetic induction, so B is correct; electric motors are made by using the force exerted by energized conductors in magnetic fields, so C Wrong; electromagnetic relays are made using the magnetic effect of current, so D is wrong. So choose B.

3. [2017•Guangxi Baise]As shown in the figure, the four positions that the generator coil passes through during one rotation in the magnetic field. The induced current in the circuit is (　D　)

A. A and B B. C and D

C. A and C D. B and D

4. [2017•Panzhihua, Sichuan]As shown in the figure, in the experiment to explore "under what circumstances can magnetism generate electricity", if the conductor AB is allowed to move upward in the vertical direction, the pointer of the sensitive galvanometer will no longer Deflection will occur; if conductor AB is allowed to move horizontally to the left, the pointer of the sensitive galvanometer will deflect. (Choose "yes" or "no" in both blanks)

Magnetic electricity PPT, part 4: layered operations

1. [2018•Leshan, Sichuan]A in the figure represents a wire perpendicular to the paper surface, which is part of a closed circuit. When it moves in the direction of the arrow in a magnetic field, it can generate induced current (D)

2. [2018•Xiangtan, Hunan]The "magnetic anomaly detector" installed on my country's new anti-submarine patrol aircraft can convert changes in the magnetic field caused by the sea area where the submarine passes into electric current, thereby detecting submarines. The figure that can explain the working principle of the "magnetic anomaly detector" is (D)

3. [2018•Shaanxi]The picture shows a model simulating wind power generation. When the motor is energized, fan a rotates at high speed to generate wind force to simulate natural wind. Fan b drives the generator to generate electricity under the action of wind force, and at the same time, the small light bulb connected to the generator emits light. Which of the following statements is correct (B)

A. When the motor rotates, it converts mechanical energy into electrical energy

B． Generators work using the phenomenon of electromagnetic induction

C. When the battery voltage decreases, the speed of fan a will not change

D. Wind strength will not affect the brightness of small light bulbs

[Analysis] When the motor rotates, it converts electrical energy into mechanical energy, so A is wrong; humans have used electromagnetic induction to make generators, so B is correct; when the battery voltage decreases, the current in the circuit will decrease, and the speed of fan A will decrease. Small, so C is wrong; when the wind force changes, the current in the circuit will change, and the brightness of the small light bulb will also change, so D is wrong. So choose B.

4. [2018•Hunan Zhuzhou]The picture shows the schematic diagram of an alternator. The coil rotates in the magnetic field, then (　B　)

A. The direction of the magnetic field between the two magnetic poles is to the left

B． The coil cuts the lines of magnetic field in the magnetic field

C. The direction of current through the bulb does not change

D. The coil must not be affected by magnetic field forces

[Analysis] The external magnetic field lines of the magnet all start from the N pole and return to the S pole, so the direction of the magnetic field between the two magnetic poles in the figure is to the right, so A is wrong; the generator is based on a part of the conductor of the closed circuit in the magnetic field. It is based on the principle of generating induced current in a conductor when cutting magnetic field lines. The direction of the induced current is related to the direction of the magnetic field and the direction of the conductor cutting the magnetic field lines. Since the direction of the conductor cutting the magnetic field lines is changing, the direction of the generated current also changes. will change, so B is correct and C is wrong; according to the principle of the force acting on the energized wire in the magnetic field, it can be known that the coil will definitely be acted upon by force at this time, so D is wrong.

5. Which statement about motors and generators is correct (D)

A.电动机是根据电磁感应现象制成的，是将电能转化为机械能的装置

B． A generator is made based on the magnetic effect of electric current and is a device that converts mechanical energy into electrical energy.

C. The rotation direction of the motor is only related to the direction of the magnetic field, which has nothing to do with other factors

D. The direction of the induced current generated by the generator is related to the direction of coil rotation and the direction of the magnetic field.

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For more information about the PPT courseware "Electricity and Magnetism: Magnetism Generates Electricity", please click the Electricity and Magnetism ppt Magnetism Generates Electricity ppt tab.

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Update Time: 2024-11-18

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