Demonstration device for thermal expansion and cold contraction

Abstract

The utility model relates to the technical field of teaching appliances, in particular to a thermal expansion and cold contraction demonstration device, which comprises a vertical support, a clamp, a metal cross rod, an alcohol lamp, a door frame, a reed pipe sensor magnetic control switch, a battery, a motor and a swing piece, the reed pipe sensor magnetic control switch comprises a permanent magnet and a reed pipe, and the permanent magnet is fixedly connected to the right end of the metal cross rod. A normally open contact is arranged in the reed pipe, the reed pipe sensor magnetic control switch is electrically connected with the motor and used for controlling starting and stopping of the motor, the battery and the motor are arranged in the swing part, the output end of the motor is connected with the swing part, and the motor drives the swing part to rotate. And the normally open contact is connected in series in a circuit in which the battery supplies power to the motor. According to the demonstration device, the metal cross rod is heated to enable the permanent magnet to make contact with the reed switch to generate a magnetic field, the experiment effect is improved through rotation of the swing piece, the experiment effect is visual, obvious and interesting, and the learning interest of students can be stimulated.

Description

Technical Field

[0001] The utility model relates to the technical field of teaching tools, in particular to a thermal expansion and contraction demonstration device. Background Art

[0002] like Figure 1 As shown, in the existing patented solution with authorization publication number CN201237846Y, the copper rod 3 undergoes thermal expansion and elongation, causing the handle 4 of the plane mirror pressed beneath it to shift, thereby affecting the position of the light spot emitted by the laser pen 7, which is reflected by the plane mirror 5 onto the wall 8. While this demonstration device can visually display the changes in thermal expansion and contraction, the small light spot requires students to stare at the spot, resulting in difficulty in observing the experimental results and a non-intuitive display. Utility Model Content

[0003] In order to solve the defects in the prior art that it is difficult for students to observe the experimental effects of thermal expansion and contraction and the display is not intuitive, so that students can observe more intuitively and reduce the difficulty of students' observation experiments, the utility model provides a thermal expansion and contraction demonstration device.

[0004] The above technical objectives of the present invention are achieved through the following technical solutions: a thermal expansion and contraction demonstration device, comprising a vertical bracket fixed on a desktop, a clamp, a metal cross bar, an alcohol lamp and a door frame placed vertically on the desktop, the vertical bracket is fixedly connected to the clamp, the left end of the metal cross bar is fixed to the vertical bracket through the clamp, the alcohol lamp is placed below the middle section of the metal cross bar, the door frame is arranged at the right end of the metal cross bar, and also includes a reed switch sensor magnetic control switch, a battery, a motor and a pendulum, the reed switch sensor magnetic control switch includes a permanent magnet and a reed switch, the permanent magnet Fixedly connected to the right end of the metal cross bar, a normally open contact is provided in the reed switch, the reed switch is fixed on the door frame, the positions of the permanent magnet and the reed switch match and the gaps correspond, under normal temperature, the normally open contact is in a disconnected state, and when the metal cross bar is heated and deformed, the normally open contact is in a connected state; the pendulum includes a base and a rotating part, the battery and the motor are both arranged in the base of the pendulum, the motor shaft of the motor is vertically upward, the rotating part is fixedly connected to the motor shaft, and the normally open contact is connected in series in the circuit in which the battery supplies power to the motor.

[0005] The above technical solution has the following advantages: Compared to existing devices, when the metal crossbar is heated, the contacts close, and the reed switch sensor's magnetic switch conducts. This closes the circuit between the reed switch sensor and the motor. At this point, the power supply provides electrical energy, and the motor drives the pendulum to rotate. This amplifies the experimental effect through the pendulum's rotation and stopping. This experimental effect is intuitive, obvious, and interesting, which can stimulate students' learning interest.

[0006] The present invention is further configured such that the permanent magnet is adjustably mounted on the metal crossbar.

[0007] The present invention is further configured such that the permanent magnet is threadedly connected to the metal cross bar.

[0008] By adopting the above technical solution, the distance between the permanent magnet and the reed switch can be adjusted. Compared with moving the vertical bracket or adjusting the position of the clamp to adjust the position of the metal cross bar, it is more convenient and quicker and more adaptable to adjusting a small distance.

[0009] The utility model is further configured such that the metal cross bar is a copper tube.

[0010] By adopting the above technical solution, among common metals, aluminum has a large thermal expansion and contraction variation. At 0-100°C, the length of aluminum increases by 23.1 microns for every 1°C temperature change. This allows for a better control of the distance between the copper tube and the reed switch, and the copper tube does not need to be heated for too long in order for the magnetic force of the permanent magnet to act on the contacts of the reed switch.

[0011] The present invention is further configured such that the reed switch is fixed to the middle of the door frame, and the reed switch, the permanent magnet and the metal cross bar are all located on the same vertical plane. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without expending any novel work.

[0013] Figure 1 It is a three-dimensional schematic diagram of a device for displaying the thermal expansion and contraction of solids in the prior art;

[0014] Figure 2 It is a three-dimensional schematic diagram of the thermal expansion and contraction demonstration device of the utility model. DETAILED DESCRIPTION

[0015] The present invention will be described in further detail below with reference to the accompanying drawings.

[0016] like Figure 2 As shown, a thermal expansion and contraction demonstration device includes a vertical bracket 1 fixed on a desktop, a clip 2, a copper tube 3, an alcohol lamp 4 and a door frame 7 placed vertically on the desktop, the vertical bracket 1 is fixedly connected to the clip 2, the left end of the copper tube 3 is fixed to the vertical bracket 1 through the clip 2, the alcohol lamp 4 is placed below the middle section of the copper tube 3, the door frame 7 is arranged at the right end of the copper tube 3, and also includes a reed switch sensor magnetic control switch, a battery, a motor and a pendulum, the reed switch sensor magnetic control switch includes a permanent magnet 5 and a reed switch 6, the permanent magnet 5 is fixedly connected to the right end of the copper tube 3, a normally open contact is provided in the reed switch 6, the reed switch 6 is fixed on the door frame 7, the positions of the permanent magnet 5 and the reed switch 6 match, and the gap corresponds. Under normal temperature conditions, the normally open contact is in a disconnected state, and when the copper tube 3 is heated and deformed, the normally open contact is in a closed state. In the connected state; that is, under normal temperature, the size of the gap can ensure that the normally open contact is not affected by the magnetic force generated by the permanent magnet 5 and the contact is closed, but when the copper tube 3 is heated and deformed, the size of the gap can ensure that the normally open contact is affected by the magnetic force generated by the permanent magnet 5 and the normally open contact is closed, so that the switch is turned on; the pendulum includes a base 81 and a rotating part 82, the battery (not shown in the figure) and the motor (not shown in the figure) are both arranged in the base 81 of the pendulum, the motor shaft of the motor vertically extends upward from the base 81, the rotating part 82 is fixedly connected to the motor shaft, the normally open contact is connected in series in the circuit in which the battery supplies power to the motor, and the reed switch sensor magnetic control switch controls the electrical connection of the motor to be disconnected or connected, that is, the reed switch sensor magnetic control switch is used to control the start and stop of the motor, and the motor drives the pendulum to rotate.

[0017] Furthermore, the permanent magnet 5 is mounted at the right end of the copper tube 3 in an adjustable position. Specifically, the permanent magnet 5 is threaded onto the right end of the copper tube 3. The reed switch is fixed to the middle of the door frame. The reed switch, the permanent magnet, and the metal crossbar are all located on the same vertical plane. The reed switch 6 uses a normally open contact. When the permanent magnet 5 approaches the reed switch 6, the contact becomes closed. When the permanent magnet 5 moves away from the reed switch 6, the contact becomes open. The motor adopts.

[0018] Working principle: Under normal temperature, a certain gap is maintained between the permanent magnet 5 and the reed switch 6, and the normally open contact of the reed switch 6 is in the disconnected state, at which time the pendulum is in a stationary state; when the alcohol lamp 4 is used to heat the copper tube 3, since the left end of the copper tube 3 is fixed to the vertical bracket 1 by the clip 2, the copper tube 3 deforms and elongates to the right due to thermal expansion, causing the permanent magnet 5 fixed to the right end of the copper tube 3 to move to the right, and the gap between the permanent magnet 5 and the reed switch 6 is reduced. As a result, under the action of the magnetic force of the permanent magnet 5, the contacts are closed, and the magnetic control switch of the reed switch sensor controls the circuit between the battery and the motor to be closed. At this time, the power supply provides power to the motor, and the motor drives the pendulum to rotate; after the alcohol lamp is stopped, the copper tube 3 gradually cools down naturally, and the copper tube 3 drives the permanent magnet 5 to move to the left, the gap between the permanent magnet 5 and the reed switch 6 is expanded, the contacts are disconnected, and the magnetic control switch of the reed switch sensor controls the circuit between the battery and the motor to be disconnected, and the pendulum stops swinging.

[0019] The motor in this technical solution can be a DC low-power motor of various models. Reed switches are also commonly used electrical components, and those skilled in the art can select one based on their needs. Compared to existing devices, the thermal expansion and contraction demonstration device using this technical solution can amplify the experimental effect through the use of a pendant. The experimental effect is intuitive, obvious, and interesting, which can stimulate students' learning interest.

[0020] It should be noted that the words indicating direction in this article, such as up and down, are all based on Figure 2 The setting of the direction is only for the convenience of description and has no other specific meaning.

[0021] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help you understand the core concept of the present invention. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from the principles of the present invention, and such improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A thermal expansion and contraction demonstration device, comprising a vertical bracket fixed on a desktop, a clamp, a metal crossbar, an alcohol lamp, and a door frame placed vertically on the desktop, wherein the vertical bracket is fixedly connected to the clamp, the left end of the metal crossbar is fixed to the vertical bracket by the clamp, the alcohol lamp is placed below the middle section of the metal crossbar, and the door frame is arranged at the right end of the metal crossbar, characterized in that: It also includes a reed switch sensor magnetic switch, a battery, a motor and a pendulum. The reed switch sensor magnetic switch includes a permanent magnet and a reed switch. The permanent magnet is fixedly connected to the right end of the metal cross bar. A normally open contact is provided in the reed switch. The reed switch is fixed on the door frame. The positions of the permanent magnet and the reed switch match and the gaps correspond. Under normal temperature conditions, the normally open contact is in a disconnected state. When the metal cross bar is heated and deformed, the normally open contact is in a connected state. The pendulum includes a base and a rotating part. The battery and the motor are both provided in the base of the pendulum. The motor shaft of the motor is vertically upward. The rotating part is fixedly connected to the motor shaft. The normally open contact is connected in series in the circuit in which the battery supplies power to the motor.

2. A thermal expansion and contraction demonstration device according to claim 1, characterized in that: The permanent magnet is adjustably mounted on the metal crossbar.

3. The thermal expansion and contraction demonstration device according to claim 2, characterized in that: The permanent magnet is threadedly connected to the metal cross bar.

4. The thermal expansion and contraction demonstration device according to claim 1, wherein: The metal crossbar is a copper tube.

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