A teaching demonstration tool for resistance law

Abstract

The utility model discloses a resistance law teaching demonstration teaching aid belongs to teaching aid technical field. The teaching aid includes backplate, is equipped with direct current source, electric bulb, ammeter, voltmeter and various resistances on backplate, and the both ends of each resistance are connected with resistance terminal post. The positive and negative poles of direct current source are connected with the wire with binding jaw, and the wire is connected with electric bulb and ammeter in series, and also can be connected with manual switch in series. Various resistances cover material, thickness, length, short and temperature comparison resistance, and can comprehensively show the influence of different factors on resistance. The voltmeter is used for measuring circuit voltage. Through the teaching aid, the relation between resistance and material, length, cross -section area and temperature can be directly shown, and the bright and dark of electric bulb and the change of ammeter value are matched, help student to understand resistance law, and operation is safe and convenient, and the teaching effect is improved.

Description

Technical Field

[0001] This utility model belongs to the field of teaching aids technology, specifically relating to a teaching demonstration aid for the law of resistance, which is used to intuitively and clearly demonstrate the relevant principles of the law of resistance during the teaching process. Background Technology

[0002] In the secondary school physics curriculum, the law of resistance is one of the core topics in electricity. It explains the quantitative relationship between the resistance of a conductor and its material, length, cross-sectional area, and temperature. A thorough understanding of the law of resistance plays a crucial role in students' grasp of circuit principles and their ability to analyze electrical problems.

[0003] However, traditional methods of teaching the law of resistance have significant drawbacks. Teachers primarily rely on blackboards and textbooks for theoretical explanations, and the abstract formulas and concepts make it difficult for students to form an intuitive understanding. Their understanding of the multiple factors affecting resistance remains superficial, failing to grasp the deep physical essence. Existing teaching demonstration tools also fail to meet teaching needs. Some tools are limited in function, only demonstrating the effect of one factor in the law of resistance, failing to comprehensively present the combined effect of multiple factors, making it difficult for students to build a complete knowledge system. Moreover, the experimental phenomena demonstrated by these tools are not obvious enough, and the demonstration process lacks interest and interactivity, failing to stimulate students' learning interest and initiative. In addition, the operation steps are cumbersome, requiring a lot of time for preparation and debugging, resulting in low classroom efficiency, easy distraction of students, and hindering the absorption and mastery of knowledge. Therefore, the development of a teaching tool that can systematically and intuitively demonstrate the law of resistance, and is easy to operate and highly engaging, is urgently needed. Utility Model Content

[0004] This invention aims to provide a teaching aid for demonstrating the law of resistance, which can intuitively display the relevant content of the law of resistance in multiple ways, help students better understand the relationship between current, voltage and resistance, as well as the influence of different factors on resistance, and improve teaching effectiveness.

[0005] The purpose of this utility model is achieved as follows: a teaching demonstration tool for the law of resistance includes a back panel, a DC power supply, a light bulb, an ammeter, a voltmeter and various resistors set on the back panel, with resistor terminals connected to both ends of each resistor.

[0006] The positive and negative terminals of the DC power supply are connected to the positive current wire and the negative current wire, respectively. The ends of the positive current wire and the negative current wire are connected to current terminals for easy connection to different resistors.

[0007] A light bulb and an ammeter are connected in series on either the positive or negative current conductor. The change in the brightness of the light bulb visually reflects the magnitude of the current, while the ammeter accurately measures the current value in the circuit.

[0008] The various resistors mentioned include material comparison resistors, thickness comparison resistors, length comparison resistors, and temperature comparison resistors.

[0009] The material comparison resistors include manganese copper alloy resistors and nickel-chromium alloy resistors with the same length and thickness. By switching between these two different materials, the influence of different materials on the resistance can be visually demonstrated.

[0010] Thickness comparison resistors include thick and thin resistors of the same length and material, which can show the relationship between the thickness of the resistor and its resistance value;

[0011] The length comparison resistors include long resistors, medium resistors, and short resistors with the same material and thickness, which are used to demonstrate the effect of resistor length on resistance value;

[0012] Temperature comparator resistors include those with positive and negative temperature correlation. Positive temperature correlation resistors consist of a wire and a tungsten filament coil connected in series with the wire. Negative temperature correlation resistors consist of a wire and a semiconductor thermistor connected in series with the wire. The effect of temperature change on resistance can be observed by heating the tungsten filament coil and the semiconductor thermistor using a lighter, alcohol lamp, or blowtorch.

[0013] The voltmeter is connected to both the positive and negative voltage leads, with the ends of the leads connected to voltage terminals. The voltmeter measures the voltage across a circuit in real time. When used in conjunction with an ammeter, it provides a more comprehensive demonstration of the quantitative relationship between current, voltage, and resistance as defined by the law of resistance.

[0014] Preferably, a manual switch is connected in series with either the positive or negative current conductor. The manual switch controls the on / off state of the circuit, making it convenient to disconnect the circuit when replacing resistors or performing other operations, ensuring operational safety. It also allows students to observe the changes in the light bulb and ammeter when the circuit is switched on and off.

[0015] Preferably, the tungsten wire coil comprises a ceramic rod on which a tungsten wire is spirally wound. This is beneficial for increasing the heated area of ​​the tungsten wire and improving the resistance change effect.

[0016] Preferably, the resistor terminal is a magnetic terminal, which includes a magnetic terminal block and a terminal post.

[0017] Preferably, a current terminal block connector and a voltage terminal block connector with the same structure as the magnetic terminals are provided on the back plate. These are used to suspend the positive current conductor, the negative current conductor, the positive voltage conductor, and the negative voltage conductor, preventing the conductors from becoming tangled.

[0018] Preferably, a support is provided at the lower end of the back panel, and a handle is provided at the upper end of the back panel.

[0019] Compared with the prior art, the beneficial effects of this utility model include:

[0020] (1) Multi-dimensional demonstration: Through different resistor modules, the system demonstrates the influence of material, length, cross-sectional area and temperature on the resistor.

[0021] (2) Dynamic visualization: The changes in the brightness of the light bulb and the changes in the ammeter reading form a dual feedback.

[0022] (3) Safe and convenient: Magnetic terminals enable quick connection, and manual switches ensure safe operation.

[0023] (4) Improved teaching efficiency: The modular design supports plug-and-play functionality, and various experimental combinations meet different teaching needs. Attached Figure Description

[0024] Figure 1 This is the front view of the teaching demonstration tool for the law of resistance of this utility model;

[0025] Figure 2 This is a three-dimensional structural diagram of the teaching aid for demonstrating the law of resistance of this utility model;

[0026] Figure 3 This is a three-dimensional structural diagram of the resistor terminal and current terminal of this utility model (the voltage terminal and the current terminal have the same structure).

[0027] Figure 4 This is a three-dimensional structural diagram of the tungsten wire coil of this utility model.

[0028] In the diagram: 1. Backplate, 2. Support, 3. Handle, 4. DC power supply, 5. Light bulb, 6. Ammeter, 7. Voltmeter, 8. Resistor terminal, 9. Positive current lead, 10. Negative current lead, 11. Current terminal claw, 12. Manganese copper alloy resistor, 13. Nickel-chromium alloy resistor, 14. Thick resistor, 15. Thin resistor, 16. Long resistor, 17. Medium resistor, 18. Short resistor, 19. Temperature-dependent resistor, 20. Temperature-independent resistor, 21. Tungsten wire coil, 22. Semiconductor thermistor, 23. Positive voltage lead, 24. Negative voltage lead, 25. Voltage terminal claw, 26. Manual switch, 27. Ceramic rod, 28. Tungsten wire, 29. Magnetic terminal block, 30. Terminal post, 31. Current terminal claw connector, 32. Voltage terminal claw connector. Detailed Implementation

[0029] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0030] Example 1: As shown in Figures 1 to 4, a teaching aid for demonstrating the law of resistance includes a back plate 1, a support 2 at the lower end of the back plate 1, and a handle 3 at the upper end of the back plate 1. A DC power supply 4, a light bulb 5, an ammeter 6, a voltmeter 7, and various resistors are mounted on the back plate 1, with each resistor connected to resistor terminals 8 at both ends. The positive and negative terminals of the DC power supply 4 are connected to a positive current conductor 9 and a negative current conductor 10, respectively, with current terminals 11 connected to the ends of both conductors. The light bulb 5 and the ammeter 6 are connected in series to the negative current conductor 10, and a manual switch 26 is connected in series to the positive current conductor 9. The voltmeter 7 is connected to a positive voltage conductor 23 and a negative voltage conductor 24, with voltage terminals 25 connected to the ends of both conductors. The various resistors include material comparison resistors, thickness comparison resistors, length comparison resistors, and temperature comparison resistors. The material comparison resistors include manganese-copper alloy resistor 12 and nickel-chromium alloy resistor 13 with consistent length and thickness; the thickness comparison resistors include thick resistor 14 and thin resistor 15 with consistent length and material; the length-short comparison resistors include long resistor 16, medium resistor 17, and short resistor 18 with consistent material and thickness; the temperature comparison resistors include temperature-positively correlated resistor 19 and temperature-negatively correlated resistor 20. Temperature-positively correlated resistor 19 includes a wire and a tungsten wire coil 21 connected in series on the wire; temperature-negatively correlated resistor 20 includes a wire and a semiconductor thermistor 22 connected in series on the wire. The tungsten wire coil 21 includes a ceramic rod 27 with tungsten metal wire 28 spirally wound on it. The resistor terminal 8 is a magnetic terminal, including a magnetic terminal block 29 and a terminal post 30. Two current terminal claw connectors 31 and two voltage terminal claw connectors 32 with the same structure as the magnetic terminal are also provided on the back plate 1.

[0031] 1. Material comparison experiment:

[0032] (1) Experimental procedure: Close the manual switch 26, connect the current terminal 11 to the resistance terminal 8 of the manganese copper alloy resistor 12, observe the brightness of the light bulb 5, and record the reading I1 of the ammeter 6 and the reading U1 of the voltmeter 7 at this time. According to the resistance law formula R=ρ×S / l, the length of the manganese copper alloy resistor is l1 and the cross-sectional area is S1. Let its resistivity be ρ1, then its resistance R1=ρ1×S1 / l1.

[0033] (2) Resistor replacement operation: Disconnect the manual switch 26, remove the current terminal 11 from the resistor terminal 8 of the manganese copper alloy resistor 12, and connect it to the resistor terminal 8 of the nickel-chromium alloy resistor 13.

[0034] (3)Re - measurement and analysis: Close the manual switch 26 again, observe the difference in the brightness of the light bulb 5 at this time compared with before, and record the reading I2 of the ammeter 6 and the reading U2 of the voltmeter 7. The length of the nickel - chromium alloy resistor is l2 (equal to l1), the cross - sectional area is S2 (equal to S1), and assuming its resistivity is ρ2, then its resistance R2 = ρ2×S2 / l2.

[0035] (4)Experimental conclusion: Compare the brightness of the light bulb 5, the reading of the ammeter 6, and the reading of the voltmeter 7 in the two experiments. Since the lengths l and cross - sectional areas S of the two resistors are the same, but the readings of the ammeter are different, it indicates that the passing currents are different. According to R = ρ×S / l, this is because the resistivities ρ of different materials are different, thus intuitively demonstrating that the resistance is related to the material. If the brightness of the light bulb 5 is different, it means that the resistances of different materials have different hindering effects on the current, that is, the resistance values are different.

[0036] 2. Thickness comparison experiment:

[0037] (1)Measurement and analysis of the thick resistor: Close the manual switch 26, connect the current connection claw 11 to the resistance terminal 8 of the thick resistor 14, observe the brightness of the light bulb 5, and record the reading I3 of the ammeter 6 and the reading U3 of the voltmeter 7 at this time. Let the length of the thick resistor be l3, the cross - sectional area be S3, and the resistivity be ρ3. According to the resistance law formula, its resistance R3 = ρ3×S3 / l3.

[0038] (2)Measurement and analysis of the thin resistor: Open the manual switch 26, remove the current connection claw 11 from the resistance terminal 8 of the thick resistor 14, and connect it to the resistance terminal 8 of the thin resistor 15. Close the manual switch 26 again, observe the difference in the brightness of the light bulb 5 at this time compared with before, and record the reading I4 of the ammeter 6 and the reading U4 of the voltmeter 7. The length of the thin resistor is l4 (equal to l3), the cross - sectional area is S4 (S4 < S3), and the resistivity is ρ4 (equal to ρ3 because the materials are the same), then its resistance R4 = ρ4×S4 / l4.

[0039] (3)Experimental conclusion: Compare the brightness of the light bulb 5, the reading of the ammeter 6, and the reading of the voltmeter 7 in the two experiments. Because the lengths l and materials (i.e., resistivities ρ) of the thick resistor 14 and the thin resistor 15 are the same, according to R = ρ×S / l, when l and ρ remain unchanged, the smaller the cross - sectional area S, the larger the resistance R. If the brightness of the light bulb 5 is different and the reading of the ammeter is different, it indicates that the thickness of the resistor affects the resistance value. The thinner the resistor, the greater the hindering effect on the current, that is, the resistance is inversely proportional to the cross - sectional area.

[0040] 3. Long and short comparison experiment:

[0041] (1)Measurement and analysis of long resistance: Close the manual switch 26, connect the current connection claw 11 to the resistance terminal 8 of the long resistance 16, observe the brightness of the light bulb 5, and record the reading I5 of the ammeter 6 and the reading U5 of the voltmeter 7 at this time. Assume the length of the long resistance is l5, the cross-sectional area is S5, and the resistivity is ρ5. According to the resistance law formula, its resistance R5 = ρ5 × S5 / l5.

[0042] (2)Measurement and analysis of medium resistance: Open the manual switch 26, remove the current connection claw 11 from the resistance terminal 8 of the long resistance 16, and connect it to the resistance terminal 8 of the medium resistance 17. Close the manual switch 26 again, observe the difference in the brightness of the light bulb 5 compared with before, and record the reading I6 of the ammeter 6 and the reading U6 of the voltmeter 7. The length of the medium resistance is l6 (l6 < l5), the cross-sectional area is S6 (equal to S5), and the resistivity is ρ6 (equal to ρ5 because the materials are the same), then its resistance R6 = ρ6 × S6 / l6.

[0043] (3)Measurement and analysis of short resistance: Open the manual switch 26, remove the current connection claw 11 from the resistance terminal 8 of 17, and connect it to the resistance terminal 8 of the short resistance 18. Close the manual switch 26, observe the difference in the brightness of the light bulb 5 compared with before, and record the reading I7 of the ammeter 6 and the reading U7 of the voltmeter 7. The length of the short resistance is l7 (l7 < l6 < l5), the cross-sectional area is S7 (equal to S5 and S6), and the resistivity is ρ7 (equal to ρ5 and ρ6 because the materials are the same), then its resistance R7 = ρ7 × S7 / l7.

[0044] (4)Experimental conclusion: Compare the brightness of the light bulb 5, the reading of the ammeter 6, and the reading of the voltmeter 7 in the three experiments. Since the materials (i.e., resistivity ρ) and cross-sectional areas S of the long resistance 16, medium resistance 17, and short resistance 18 are the same, according to R = ρ × S / l, when ρ and S remain unchanged, the longer the length l, the greater the resistance R. If the brightness of the light bulb 5 is different and the ammeter readings are different, it means that the longer the resistance length, the greater the resistance to the current, that is, the resistance is proportional to the length.

[0045] 4. Temperature comparison experiment:

[0046] (1)Temperature positively correlated resistance experiment (taking the tungsten wire coil as an example):

[0047] ① Initial State Analysis: Close the manual switch 26 and connect the current terminal 11 to the resistance terminal 8 of the temperature-dependent resistor (containing a tungsten wire coil). Observe the brightness of the light bulb 5 and record the readings I8 of the ammeter 6 and U8 of the voltmeter 7. Assume the length of the tungsten wire coil is l8, the cross-sectional area is S8, and the resistivity is ρ8. According to the resistance law formula, its resistance R8 = ρ8 × S8 / l8.

[0048] ② Observation and Analysis of the Heating Process: Slowly heat the tungsten filament coil using a heating device (such as a lighter, alcohol lamp, etc., but pay attention to safe operating distance and protection), continuously observe the changes in the brightness of the light bulb 5, and simultaneously record the real-time changes in the readings of ammeter 6 and voltmeter 7. As the temperature rises, the resistivity ρ of the tungsten filament increases. With the length l and cross-sectional area S remaining essentially constant, according to R=ρ×S / l, the resistance R increases. If the light bulb 5 dims and the ammeter 6 reading decreases, it indicates that the resistance increases with increasing temperature, demonstrating a positive correlation between temperature and resistance.

[0049] ③ Observation of the cooling process: After heating for a period of time, stop heating and wait for the tungsten wire coil to cool down naturally. Observe the gradual recovery of the brightness of the light bulb 5 and the reverse change of the readings of the ammeter 6 and voltmeter 7 to further verify the positive correlation between temperature and resistance.

[0050] (2) Temperature-negative resistance experiment (taking semiconductor thermistor as an example):

[0051] ① Initial State Analysis: Disconnect manual switch 26, remove current terminal 11 from the resistor terminal 8 of the temperature-positively correlated resistor, and connect it to the resistor terminal 8 of the temperature-negatively correlated resistor (including the semiconductor thermistor). Close manual switch 26, observe the brightness of light bulb 5, and record the readings I9 of ammeter 6 and U9 of voltmeter 7. Assume the length of the semiconductor thermistor is l9, the cross-sectional area is S9, and the resistivity is ρ9. According to the resistance law formula, its resistance R9 = ρ9 × S9 / l9.

[0052] ② Observation and Analysis of the Heating Process: Slowly heat the semiconductor thermistor using a heating device, continuously observe the changes in the brightness of the light bulb 5, and simultaneously record the real-time changes in the readings of ammeter 6 and voltmeter 7. As the temperature rises, the resistivity ρ of the semiconductor thermistor decreases. With the length l and cross-sectional area S remaining essentially constant, according to R=ρ×S / l, the resistance R decreases. If the light bulb 5 becomes brighter and the ammeter 6 reading increases as the temperature rises, it indicates that the resistance decreases with increasing temperature, demonstrating a negative correlation between temperature and resistance.

[0053] ③ Observation of the cooling process: After heating is stopped, wait for the semiconductor thermistor to cool down, observe the brightness of the light bulb 5 and the corresponding changes in the readings of the ammeter 6 and voltmeter 7, and confirm the negative correlation between temperature and resistance.

[0054] 5. Electric power calculation:

[0055] In the above-mentioned experiments, select any set of recorded ammeter 6 readings (e.g., the current I in a certain experiment) and voltmeter 7 readings (e.g., the corresponding voltage U). Substitute the recorded current and voltage values ​​into the formula P=U / I to calculate the power. For example, if I=0.5A and U=3V in a certain experiment, then the power P=0.5A×3V=1.5W. By calculating the power under different experimental conditions multiple times, students can further deepen their understanding of the law of resistance and the concept of power, and understand the relationship between power, current, and voltage.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model, and they should all be covered within the scope of the claims and specification of this utility model.

Claims

1. A teaching aid for demonstrating the law of resistance, comprising a backboard (1), characterized in that: The backplate (1) is provided with a DC power supply (4), a light bulb (5), an ammeter (6), a voltmeter (7), and various resistors; the various resistors include material comparison resistors (12, 13), thickness comparison resistors (14, 15), length comparison resistors (16, 17, 18), and temperature comparison resistors (19, 20); the DC power supply (4) is connected to the current terminal (11) through the positive current wire (9) and the negative current wire (10); the voltmeter (7) is connected to the voltage terminal (25) through the positive voltage wire (23) and the negative voltage wire (24); the resistors are connected to the circuit through the resistor terminals (8).

2. The teaching aid for demonstrating the law of resistance according to claim 1, characterized in that: A manual switch (26) is connected in series on the positive current conductor (9) or the negative current conductor (10).

3. The teaching aid for demonstrating the law of resistance according to claim 1, characterized in that: The temperature comparison resistor includes a temperature positive correlation resistor (19) and a temperature negative correlation resistor (20). The temperature positive correlation resistor (19) includes a ceramic rod (27) and a spirally wound tungsten wire (28).

4. The teaching aid for demonstrating the law of resistance according to claim 3, characterized in that: The resistor terminal (8) is a magnetic terminal, including a magnetic terminal block (29) and a terminal post (30).

5. The teaching aid for demonstrating the law of resistance according to claim 4, characterized in that: The back plate (1) is provided with a current terminal block (31) and a voltage terminal block (32).

6. The teaching aid for demonstrating the law of resistance according to any one of claims 1 to 5, characterized in that: The back panel (1) has a support (2) at the bottom and a handle (3) at the top.

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