CN110969920B

CN110969920B - Novel resonance demonstration device based on electromagnetic induction law

Info

Publication number: CN110969920B
Application number: CN202010004609.1A
Authority: CN
Inventors: 王道光; 陈斯; 王秀荣
Original assignee: Jiangsu Normal University
Current assignee: Jiangsu Normal University
Priority date: 2020-01-03
Filing date: 2020-01-03
Publication date: 2021-09-03
Anticipated expiration: 2040-01-03
Also published as: CN110969920A

Abstract

A novel resonance demonstration device based on an electromagnetic induction law comprises a fixed support, a spring, a pressure sensor, a trolley, a weight plate, a bar-shaped permanent magnet, an induction coil, an LED (light-emitting diode), a signal rectification module, an oscillator control module, a current compensation module, a small oscilloscope and a signal wire. The invention transmits mechanical force by means of Faraday's law of electromagnetic induction through the alternating current coil, thereby realizing the demonstration of various classical oscillation modes of college physical experiments, such as the demonstration of mechanical resonance phenomenon, the demonstration of forced vibration phenomenon, the demonstration of chaotic oscillation phenomenon and the like. The device establishes the cross relationship between knowledge points of mechanical resonance and electromagnetic induction law in a novel way, and can effectively improve the teaching quality of college physics and experimental courses.

Description

Novel resonance demonstration device based on electromagnetic induction law

Technical Field

The invention relates to a physical demonstration experimental instrument, in particular to a novel resonance demonstration device based on an electromagnetic induction law.

Background

The resonance phenomenon and the forced vibration law are one of the main contents of mechanical vibration part teaching in university physics. The concept of resonance frequency and the change rule of forced vibration amplitude and input frequency are the key and difficult points in the course knowledge point. The intuitive presentation of the oscillating energy transfer process is a key loop in understanding the above phenomena. At present, the traditional coupled pendulum experiment demonstration instrument is generally used in college physical teaching to show the resonance phenomenon. The demonstration instrument only observes the swinging condition by naked eyes and cannot obtain an accurate quantitative result. The instrument has single function and is not combined with other teaching knowledge points, such as electromagnetic induction rules and the like. In order to help students to understand the connotation of the knowledge points of the courses more deeply and improve the quality of the classroom, a novel resonance phenomenon demonstration instrument is necessary to be designed.

Disclosure of Invention

The invention aims to provide a novel device for demonstrating experiment phenomena such as mechanical resonance, forced vibration and the like in college physics teaching.

In order to achieve the above purpose, the technical scheme of the invention is as follows:

a novel resonance demonstration device based on the law of electromagnetic induction comprises:

the box-shaped base comprises a bottom plate and side walls, and a vibration device is fixed on one side wall of the box-shaped base;

the vibration box comprises two trolleys and two springs which are oppositely arranged, wherein one end of one spring is connected with a vibration device, one end of the other spring is fixed on the other side wall of the box-shaped base, the other ends of the two springs are respectively connected with the two trolleys, strip-shaped magnets are respectively fixed on the opposite ends of the two trolleys, and the two trolleys can slide on the box-shaped bottom;

two risers with opposite inner sides are fixed in the center of the box-shaped bottom, two cylinders which are symmetrically arranged are fixed on the outer sides of the two risers, a group of hollow multiturn coils are wound on the cylinders respectively, the two groups of hollow multiturn coils are connected through wires and then form a loop with a current compensation circuit, and two strip magnets on the trolley stretch into the two opposite cylinders respectively.

As a further preferable technical scheme, the LED lamp further comprises an LED light-emitting diode, and the LED light-emitting diode is arranged on a lead wire connected with the two groups of hollow multi-turn coils.

As a further preferred technical scheme, the device further comprises two pressure sensors, a pressure signal rectification module and an oscilloscope, wherein the two pressure sensors are respectively fixed between the spring and the trolley, the pressure sensors are connected with the pressure signal rectification module, and the pressure signal rectification module processes pressure signals collected by the pressure sensors and then sends the processed pressure signals to the oscilloscope for real-time display.

As a further preferable aspect, the vibration device includes a low-frequency dc oscillator and a stepping motor driver that controls the low-frequency dc oscillator.

As a further preferred technical scheme, the trolley is further provided with a clamping groove, and a plurality of detachable counterweight plates are installed on the clamping groove.

As a further preferable technical solution, the weight plate is rectangular parallelepiped cast iron.

As a more preferable technical scheme, the mass of the cuboid cast iron is 100 g.

As a further preferred technical scheme, the bottom plate is a wood plate, and the side walls and the vertical plates are made of transparent organic glass.

As a further preferred technical scheme, the strip-shaped permanent magnet is a neodymium iron boron strong magnet, the length of the strip-shaped permanent magnet is 15cm, the diameter of the circular cross section of the strip-shaped permanent magnet is about 5.0cm, and the magnetic field intensity of a single magnet is 800 mT.

As a further preferable technical scheme, the number of turns of the hollow multi-turn coil is 3000, the length of the coil is 20cm, and the diameter of the circular section of the coil is 5.5cm

Compared with the prior art, the invention has the beneficial effects that:

the device of the invention can automatically realize the demonstration of mechanical resonance and forced vibration phenomena, and can display the time variation curve of the vibration signal through the liquid crystal screen;

the device adopts an electromagnetic induction design, realizes the efficient transmission of the oscillation of the trolley and the spring through the mutual motion of the strong magnet and the densely wound coil, and can realize the compensation of the non-frequency conversion mode of the coil current through the rectifier module;

the device realizes the change of the quality of the vibrator by changing the number of the counterweight sheets of the trolley and the change of the natural oscillation frequency of the spring-trolley vibrator, thereby achieving the aim of generating various oscillation modes.

Drawings

FIG. 1 is a schematic structural diagram of a demonstration apparatus according to an embodiment of the present invention;

FIG. 2 is a circuit diagram of a current compensation circuit according to an embodiment of the present invention;

FIG. 3 is a signal rectification circuit for a pressure sensor according to an embodiment of the present invention;

wherein, 1-box-shaped base; 2, 19-spring; 3, 15-trolley; 4, 16-weight stack; 5, 14-bar permanent magnet; 6, 13-coil fixing cylinder; 7, 12-hollow multi-turn coil; 8-current compensation circuit A; 9, 11-riser; 10-LED light emitting diodes; 17-pressure signal transmission line; 18, 27-pressure sensor; 20-a direct current low frequency oscillator; 21-a connector; 22-motor connection line; 23-controller D; 24-a pressure signal rectification module B; 25-a signal line; 26-simple oscilloscope C.

The specific implementation mode is as follows:

the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Examples

As shown in figure 1, the novel resonance demonstration device based on the electromagnetic induction law comprises a box-shaped base 1, an oscillator control module, a vibration assembly, an electromagnetic induction module, a signal rectification module and a signal display module. The box-shaped base 1 is a cuboid transparent box, the size of the transparent box is 90cm (long) x 10cm (wide) x 30cm (high), the bottom plate is a wood plate, the side wall is made of organic glass, and two ends of the bottom of the base are respectively fixed with 2 circular rubber feet. The vertical plates 9 and 11 are fixed in the middle of the box base through screws, the sizes of the vertical plates are 10cm (width) multiplied by 30cm (height) multiplied by 2cm (thickness), the organic glass material is made of organic glass, and each plate is provided with 2 small holes with the diameter of 5 mm.

The oscillator control module includes: a low frequency dc oscillator 20 and a stepper motor driver 23 dedicated to controlling the oscillator. A low frequency dc oscillator 20 drives the cam with a dc stepper motor to produce periodic oscillations, which motor is connected to a spring 19 via a connector 21. The direct current stepping motor has a square section, the side length of 42mm, the power of 20W and the rated input voltage of 12V. The stepping motor driver 23 is composed of a pulse generation control unit, a power drive unit, a protection unit, and the like. The stepper motor driver 23 has two terminals D1 and D2 connected to the motor terminals D3 and D4 by wires 22.

The vibration assembly includes: springs 2 and 19 with moderate stiffness coefficient, trolleys 3 and 15 for experimental demonstration and weight plates 4 and 16. The individual springs 2 and 19 have a length of 10cm, a diameter of 3cm and a stiffness coefficient of 10N/m. One end of the spring 2 is fixed on the box wall through screws, and the other end is connected to the sensor 27. One end of the spring 19 is fixed to the connector 21 by a screw, and the other end is connected to the sensor 18. The carriages 3 and 15 have a single mass of 400g, a length of about 10cm and a width of about 8cm, and two wheels under them, which rub against the base in a rolling mode. The trolley is provided with clamping grooves for mounting variable number of counterweight plates, a single trolley is provided with 8 counterweight plates at most, the counterweight plates 4 and 16 are cuboid cast iron, and the mass of each single plate is 100 g. The trolley is driven by the spring to move.

The electromagnetic induction module includes: bar-shaped permanent magnets 5 and 14 with extremely strong magnetism, hollow multi-turn densely wound coils 7 and 12, coil fixing supports 6 and 13, and connecting wires. The strip permanent magnet is a neodymium iron boron strong magnet, the length of the strip permanent magnet is 15cm, the circular cross section of the strip permanent magnet is about 5.0cm, the magnetic field intensity of a single magnet is 800mT, and the N pole of the strip permanent magnet is fixed on the trolley. The hollow multi-turn densely wound coil 7 is wound on the coil fixing bracket 6, the coil 12 is wound on the coil fixing bracket 13, and the winding directions of the coil 7 and the coil 12 are opposite. The number of turns of a single coil is 3000, the cross section of the coil fixing support is circular, the coil fixing support is made of polypropylene plastics, and the diameter of the coil fixing support is 5.5 cm. The two coils are connected through a wire, the wire passes through two small holes in the hard plates 9 and 11, and the LED 10 is connected in series between the coils to display the direction of current in the circuit.

The signal rectification module includes: current compensation circuit 8 (fig. 2), pressure-

sensitive sensors

18 and 27, pressure sensor signal rectification module 24 (fig. 3), and signal input and output leads 17 and 25. After the bar-shaped permanent magnet moves in the coil, the cutting magnetic induction line generates induction current which can present the characteristic of natural attenuation. In order to ensure the stability of the experimental phenomenon, the current in the passive coil 7 needs to be compensated, and the current compensation circuit 8 is adopted in the invention. The current compensation circuit 8 adopts two circuits connected in reverse, and can amplify weak current with periodically changed direction. The pressure-

sensitive sensors

18 and 27 are fixed to the trolley at one end and to the spring at the other end, and generate pressure when the spring pulls or pushes the trolley to move, and corresponding voltage signals are generated through the

sensors

18 and 27. The sensor is based on the piezoelectric effect, is a self-power-generation type and electromechanical conversion type sensor and is made of piezoelectric materials. After the steel ball is impacted, the surface of the piezoelectric material generates electric charges. The electric charge is amplified by the charge amplifier and the measuring circuit and transformed into impedance, and then becomes electric quantity output related to external force. The voltage signal is input to the pressure sensor signal rectification module 24 via conductor 17 at interfaces IN1 and IN 2. The rectifying circuit is responsible for carrying out a method and transforming impedance on the electric charge input by the piezoelectric sensor. This function is implemented using an LM358 chip. After being rectified, the signals are output through interfaces O1 and O2.

The signal display module includes: a simple oscilloscope 26, showing low frequency signals, is shown, with signal input lead 25. The pressure signal is adjusted by the signal rectification module 24 and then input into the simple oscilloscope 26 through the signal line 25, so that the real-time display of the pressure signal is realized. The liquid crystal display is provided with a display driver and is formed into a single chip. The single chip microcomputer chip is responsible for carrying out A/D conversion on the input signals, so that the input signals can be identified and displayed for the liquid crystal display.

The invention is based on the electromagnetic induction law, adopts a spring and an electromagnet to carry out intuitive resonance experiment demonstration, and has the following working procedures:

an oscillation frequency is set in a stepping motor driver 23, a low frequency direct current oscillator 20 is started through a signal line 22 to generate periodic oscillation, and the oscillation is conducted to a spring 19 through a connector 21. The spring 19 acts on the trolley 15 through the pressure sensor 18. The trolley 15 drives the strong magnet 14 fixed at one end of the trolley to move, and the strong magnet 14 performs cutting magnetic induction line motion in the coil 12 to form an active vibrator Z1. Wherein the coil is fixed on the rectangular parallelepiped plate 11. According to Lenz's law, induced current is generated, and the magnitude of the induced current meets Faraday's law of electromagnetic induction. Then, the induced current is conducted to the coil 7 through the lead and the light emitting diode 10. A magnetic field will be generated according to the magnetic effect of the current, and the direction of the magnetic field meets the right-hand helical rule. The magnetic field acts on the strong magnet 7 of the same structure in the coil 7 to make forced movement, so that a vibrator Z2 is formed. Then, the strong magnet 7 drives the trolley 3 and the balance weight 4 to move. The spring 2 is brought into oscillation by the pressure sensor 27. Wherein the spring 2 is fixed on the base 1. Then, the spring 2 drives the trolley and the strong magnet 5 to move, cuts the magnetic induction line, generates reverse current, and counteracts on the coil 12 and the strong magnet 14 magnets to complete a cycle.

When the external force is a periodic driving force, the vibrators Z1 and Z2 are forced to vibrate and have the same frequency; when the external force is removed, the vibration frequency of the vibrators Z1 and Z2 depends on the stiffness coefficient k of the respective springs, the mass of the strong magnet, the mass of the trolley and the mass of the counterweight. If the spring stiffness coefficient k, the magnet mass, the trolley mass and the counterweight mass in the two sets of vibrators are completely the same, the vibration of the two magnets resonates, and the amplitude is maximum. The arrangement uses means 8 to improve the current decay due to the weaker current in the coil. The amplifying circuit adopts a simple operational amplifying circuit with a diode to bidirectionally compensate the current in the two coils. The circuit adopts a non-frequency conversion mode to compensate current. When the natural frequencies of the two magnet vibrators Z1 and Z2 are close to each other, the vibrators Z1 and Z2 respond optimally to the driving force. When the driving is carried out by the aperiodic external force, the natural frequencies of the vibrators Z1 and Z2 are different, the loading balance weight of the trolley is changed, and the loop can display chaotic oscillation with different appearances.

The core part of the device uses an STM32 type singlechip control circuit, so that the oscillation of the magnet can be presented in a quantitative mode. In order to accurately measure the amplitude, a white board with scales is arranged behind the spring 2 and the spring 19 so as to clearly display the position of the magnet when the magnet stably vibrates, and therefore the amplitude is read.

In order to show the vibration effect of the magnet in real time, the device uses a simple oscilloscope which is independently manufactured. The oscilloscope module 26 is based on an STM32 singlechip, and reads data by using an I/O (input/output) port analog single bus of the singlechip through manual programming. The device uses an independent liquid crystal screen 26, and can highlight the frequency of forced vibration of the spring vibrator.

Claims

1. A novel resonance demonstration device based on the law of electromagnetic induction is characterized by comprising:

the vibration box comprises two trolleys and two springs which are oppositely arranged, wherein one end of one spring is connected with a vibration device, one end of the other spring is fixed on the other side wall of the box-shaped base, the other ends of the two springs are respectively connected with the two trolleys, strip-shaped permanent magnets are respectively fixed on the opposite ends of the two trolleys, and the two trolleys can slide on the box-shaped bottom;

two vertical plates with opposite inner sides are fixed in the center of the box-shaped bottom, two cylinders which are symmetrically arranged are fixed on the outer sides of the two vertical plates, a group of hollow multiturn coils are wound on each cylinder, the two groups of hollow multiturn coils are connected through wires and then form a loop with a current compensation circuit, and two strip-shaped permanent magnets on the trolley stretch into the two opposite cylinders respectively.

2. The novel resonance demonstration device based on the law of electromagnetic induction as claimed in claim 1, characterized by further comprising an LED light emitting diode mounted on the wire connecting the two sets of hollow multi-turn coils.

3. The novel resonance demonstration device based on the electromagnetic induction law according to claim 1, further comprising two pressure sensors, a pressure signal rectification module and an oscilloscope, wherein the two pressure sensors are respectively fixed between the spring and the trolley, the pressure sensors are connected with the pressure signal rectification module, and the pressure signal rectification module processes the pressure signals collected by the pressure sensors and then sends the processed pressure signals to the oscilloscope for real-time display.

4. A novel resonance demonstrating device based on the law of electromagnetic induction, according to claim 1, characterized in that said vibration device comprises a low frequency dc oscillator and a step motor driver controlling the low frequency dc oscillator.

5. The novel resonance demonstration device based on the electromagnetic induction law as claimed in claim 1, wherein the trolley is further provided with a clamping groove, and a plurality of detachable weight plates are mounted on the clamping groove.

6. The novel resonance demonstration device based on the law of electromagnetic induction as claimed in claim 5, characterized in that the weight plates are cuboid cast iron.

7. A novel resonance demonstration device based on the law of electromagnetic induction as claimed in claim 6, characterized in that the rectangular parallelepiped cast iron has a mass of 100g。

8. The novel resonance demonstration device based on the law of electromagnetic induction of claim 1 wherein the bottom plate is a wooden plate and the side walls and risers are transparent plexiglass.

9. A novel resonance demonstration apparatus based on the law of electromagnetic induction as claimed in claim 1, characterized in thatThe strip-shaped permanent magnet is neodymium iron boron strong magnet, and the length of the strip-shaped permanent magnet is 15 cmAnd a circular cross-sectional diameter of about 5.0cmMagnetic field strength of a single magnet is 800mT。

10. The novel resonance demonstration device based on the law of electromagnetic induction as claimed in claim 1, wherein the number of turns of the hollow multi-turn coil is 3000, and the length of the coil is 20 cmThe diameter of the circular section of the coil is 5.5cm。