Teaching aid for quantitatively comparing thermal expansion and cold contraction degrees of different metals

Abstract

The utility model provides a teaching aid for quantitatively comparing thermal expansion and cold contraction degrees of different metals. The device comprises a base, an electronic depth vernier caliper, an L-shaped steel plate and long-strip-shaped metal. An L-shaped steel plate is fixed to one end of the base, at least two pieces of long-strip-shaped metal arranged in parallel are further arranged above the base, the left sides of the long-strip-shaped metal abut against the L-shaped steel plate, and in other words, the contact position of the left end of the long-strip-shaped metal and the L-shaped steel plate is the fixed end of the long-strip-shaped metal. The right end of the long-strip-shaped metal is a free end which expands and extends when heated, the free end is connected with the electronic depth vernier caliper, and the number of the long-strip-shaped metal is consistent with that of the electronic depth vernier caliper. A plurality of identical heat sources are placed below the long-strip-shaped metal, and one heat source is placed below each long-strip-shaped metal. The utility model solves the problems that the traditional teaching aid cannot replace test materials and cannot prove that other metals have thermal expansion and cold contraction properties; according to the utility model, the metal expansion process is visually reflected, and the thermal expansion and cold contraction performance differences of different metals are compared.

Description

Technical Field

[0001] The utility model belongs to the field of teaching aids. Background Art

[0002] Electronic depth vernier caliper: An electronic measuring tool for measuring depth or length, with the function of electronically reading the length (including length change) value. Many metals such as copper, iron, and aluminum will expand in volume when heated and shrink in volume when cooled. This phenomenon is called thermal expansion and contraction of metals. "Thermal expansion and contraction" is an important content in primary school science courses. In the "Primary School Science Curriculum Standards", the academic requirements for the teaching content of "thermal expansion and contraction" include four aspects: 1. Know the properties of thermal expansion and contraction and its application examples in production and life; 2. Be able to summarize the thermal expansion and contraction properties of objects with examples; 3. Be able to design experiments to explore the thermal expansion and contraction phenomena of common objects; 4. Be willing to use thermal expansion and contraction and other related principles to solve some problems in life. Therefore, in the teaching of "thermal expansion and contraction" in primary school science and even junior and senior high school physics, it is necessary to use relevant teaching aids to help students intuitively see the phenomenon of metal heating and contraction and the differences in the degree of thermal expansion and contraction of different metals.

[0003] Currently, the most common teaching aid to prove the "thermal expansion and contraction" property of metal is the copper ball thermal expansion and contraction perforation teaching aid. The phenomenon that a cold copper ball can pass through an iron ring, while the copper ball that expands due to heat cannot pass through the iron ring is used to prove that the copper ball expands when heated.

[0004] The existing copper ball thermal expansion and contraction perforation teaching aids have the following disadvantages:

[0005] 1. The test material cannot be changed, and it is impossible to prove that other metals also have the property of thermal expansion and contraction;

[0006] 2. It is impossible to compare the differences in thermal expansion and contraction properties of different metals;

[0007] 3. It is impossible to directly reflect the process of metal expansion;

[0008] 4. It is impossible for students to quantitatively observe the degree and length of metal expansion. Summary of the invention

[0009] The teaching aid for quantitatively comparing the thermal expansion and contraction of different metals described in the utility model mainly consists of a base, two electronic depth vernier calipers (also known as tire tread measuring rulers), a double-headed alcohol lamp, and two long strips of metal made of different materials. The connection diagram is as shown in FIG. Figure 1 shown.

[0010] A teaching aid for quantitatively comparing the thermal expansion and contraction of different metals, characterized by comprising:

[0011] Base (1), electronic depth vernier caliper, L-shaped steel plate (8), double-head alcohol lamp (4) and long metal strip;

[0012] An L-shaped steel plate is fixed to one end of the base (1), and at least two parallel long strips of metal are arranged above the base (1), and the left side of the long strip of metal abuts against the L-shaped steel plate (8), that is, the left end of the long strip of metal and the L-shaped steel plate (8)

[0013] The contact position is the fixed end of the long metal strip; the right end of the long metal strip is a free end that expands due to heat, and the free end is connected to the electronic depth vernier caliper, and the number of the long metal strip and the electronic depth vernier caliper is the same;

[0014] A plurality of identical heat sources are placed under the long metal strip, with one heat source being placed under each long metal strip.

[0015] Further, a long strip of metal is placed above the steel gasket (9).

[0016] The L-shaped steel plate (8) and the steel gasket (9) both play a role in heat insulation. The bolts on the steel gasket are used to ensure that the long strips of metal are placed in parallel. The L-shaped steel plate (8) ensures that the left end of the long strip of metal is fixed and the right end is free to expand.

[0017] Furthermore, the cross section of the base is set to be concave.

[0018] Furthermore, the size of the long metal strip is 25 cm×1 cm×0.2 cm.

[0019] Furthermore, the number of the long metal strips and the number of the electronic depth vernier calipers are both two.

[0020] Furthermore, the heat source adopts a double-head alcohol lamp (4) or two identical alcohol lamps.

[0021] Effects of the utility model

[0022] 1. Solve the problem that traditional teaching aids cannot replace test materials and cannot prove that other metals also have the property of thermal expansion and contraction;

[0023] 2. Solve the problem that traditional teaching aids cannot compare the differences in thermal expansion and contraction properties of different metals;

[0024] 3. Solve the problem that traditional teaching aids cannot directly reflect the metal expansion process;

[0025] 4. Solve the problem that traditional teaching aids cannot allow students to quantitatively observe the degree and length of metal expansion. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of a teaching aid for quantitatively comparing the thermal expansion and contraction of different metals

[0027] Figure 1In the figure, 1 is a base, 2 is a first electronic depth vernier caliper, 3 is a second electronic depth vernier caliper, 4 is a double-headed alcohol lamp, 5 is a long strip of metal of the first material, 6 is a long strip of metal of the second material, 7 is a limit device, 8 is an L-shaped steel plate, and 9 is a steel gasket. DETAILED DESCRIPTION

[0028] The base (1) is concave and is used for placing an electronic depth vernier caliper, fixing an L-shaped steel plate (8), fixing a steel gasket (9), placing a double-head alcohol lamp (4) and placing long strips of metal. The size of each long strip of metal is approximately 25 cm×1 cm×0.2 cm.

[0029] The recessed position of the base (1) is used to place a double-headed alcohol lamp (4). The double-headed alcohol lamp (4) is placed directly below the middle of the long metal strip. Since the double-headed alcohol lamp (4) uses the same wick and fuel and is ignited at the same time, it can provide the same heating energy for the two long metal strips. The double-headed alcohol lamp (4) can be replaced by a double-headed oil lamp, two identical alcohol lamps, two identical oil lamps, or other heating devices that can provide the same heat source.

[0030] Two long metal strips are placed in parallel on the L-shaped steel plate (8) and the steel gasket (9), and the two long metal strips are placed in parallel by the limit device (7). The left side of the long metal strip is against the L-shaped steel plate (8), and the contact position between the left end of the long metal strip and the L-shaped steel plate (8) is the fixed end of the long metal strip that expands and extends when heated, and the right end of the long metal strip is the free end of the long metal strip that expands and extends when heated. The L-shaped steel plate (8) and the steel gasket (9) also play a role in heat insulation, preventing the long metal strip from directly contacting the base and causing damage after being heated.

[0031] The two electronic depth vernier calipers, namely the first electronic depth vernier caliper (2) and the second electronic depth vernier caliper (3), are respectively on the same straight line with the corresponding two long strips of metal, namely the long strip of metal (5) of the first material and the long strip of metal (6) of the second material.

[0032] If you need to measure the thermal shrinkage of three or more long metal strips at the same time, increase the number of long metal strips and add corresponding electronic depth vernier calipers and heating devices.

[0033] This experimental teaching aid uses the principle of "magnification" to make the difficult-to-observe thermal expansion and contraction of metals easier to observe, and even to display them quantitatively. This teaching aid mainly achieves the following three "magnifications":

[0034] (1) The first enlargement of the teaching aid

[0035] When metal is heated, it will generally expand freely in all directions, and it is difficult to measure the actual change value of the metal. In this experiment, one end of the metal is fixed, and the other end is allowed to expand freely after being heated, so that the expansion change of the metal at both ends is concentrated to one end (the free end), achieving the first amplification.

[0036] (2) Second enlargement of teaching aids

[0037] When metal expands due to heat, its volume increases as a whole. In order to more intuitively observe the changes in metal expansion and contraction and amplify the changes in metal expansion, this experiment selected a long strip of metal (about 25 cm in length, 2 mm in thickness, and 1 cm in width) as the experimental object, and took the change in its longitudinal length (25 cm in the direction of length change) as the observation object to achieve the accumulation and amplification of the expansion length, making it easier to observe the change in length and achieve a second amplification.

[0038] (3) The third enlargement of the teaching aids

[0039] This teaching aid uses the mechanical magnification principle of the vernier caliper to measure the change in the length of a long metal strip before and after heating, and amplifies the experimental results to achieve the third magnification.

[0040] The use process of the teaching aid for quantitatively comparing the thermal expansion and contraction of different metals:

[0041] (1) Placement: Place the two long metal strips to be measured on the bracket, with the left end of the long metal strip against the L-shaped steel plate, and the right side of the long metal strip against the metal measuring end of the electronic depth vernier caliper, and then return the electronic depth vernier caliper to zero.

[0042] (2) Heating: Place the double-ended alcohol lamp at the lower end of the long metal strip and use a lighter to ignite the two wicks of the double-ended alcohol lamp at the same time.

[0043] (3) Observe the change in the value of metal thermal expansion: Observe the change in the value displayed by the electronic depth vernier caliper caused by the change in the length of the long metal strip after heating.

[0044] (4) Record: After heating for 5-8 minutes, if the value of the electronic depth vernier caliper remains stable, it means that the long strip of metal has expanded to its limit. Record the value. The value displayed on the screen is the change in length of the long strip of metal after thermal expansion (unit: mm).

[0045] (5) Observe the change in the metal shrinkage value: reset the electronic depth vernier caliper to zero, then remove the double-headed alcohol lamp from the bracket and extinguish the double-headed alcohol lamp. Allow the long strip of metal to cool naturally to room temperature. Press the metal measuring end of the electronic depth vernier caliper against the right side of the long strip of metal and observe the change in the value displayed on the electronic depth vernier caliper due to the change in length of the long strip of metal after shrinkage.

[0046] (6) Record: The value displayed on the screen is the change in length of the long strip of metal after it shrinks due to cooling (unit: mm). Record the value.

[0047] 1. Prove that metals will expand when heated and contract when cooled under the same conditions, that is, thermal expansion and contraction. Place a 25 cm iron bar and a 25 cm copper bar on the teaching aids and heat them with a double-headed alcohol lamp. The values ​​of the electronic depth vernier caliper corresponding to the iron bar and the copper bar will increase, proving that the iron bar and the copper bar will become longer when heated, that is, thermal expansion will occur. Reset the electronic depth vernier caliper to zero, then remove the double-headed alcohol lamp from the bracket and extinguish the double-headed alcohol lamp. Let the long iron bar and the long copper bar cool naturally to room temperature. Press the metal measuring end of the electronic depth vernier caliper against the right side of the long metal. Observe the change in the length change of the long metal after the cold contraction, which is caused by the change in the value displayed by the electronic depth vernier caliper. This proves that the iron bar and the copper bar will become shorter when cooled, that is, cold contraction will occur.

[0048] 2. Prove that different metals expand differently under the same conditions. Place a 25 cm iron bar and a 25 cm copper bar on the teaching aid. The values ​​of the electronic depth vernier calipers corresponding to the iron and copper bars increase. After heating with a double-headed alcohol lamp for about 7 minutes, the values ​​of the electronic depth vernier calipers corresponding to the iron and copper bars stabilize. The iron bar expands by 0.48 mm, and the copper bar expands by 0.72 mm, proving that the thermal expansion coefficient of copper is greater than that of the iron bar.

[0049] 3. Observe the process of metal expansion due to heat. Place a 25 cm iron bar and a 25 cm copper bar on the teaching aid and heat them with a double-headed alcohol lamp. The values ​​of the electronic depth vernier caliper corresponding to the iron bar and the copper bar gradually increase. After 7 minutes of heating, the values ​​of the electronic depth vernier caliper corresponding to the iron bar and the copper bar are stable. The gradual increase in the values ​​of the electronic depth vernier caliper reflects the process of metal expansion due to heat. When the values ​​are stable, it means that the metal has reached its limit of expansion due to heat.

[0050] 1. This teaching aid provides a variety of common metals such as copper, iron, aluminum, etc., and any other metal can also be replaced.

[0051] 2. This teaching aid can measure the thermal expansion and contraction properties of two metals at the same time, and intuitively show the differences in the expansion and contraction properties of the two metals. The differences in expansion and contraction properties include the speed of thermal expansion (fast or slow), the degree of expansion (length), the proportion of expansion, etc. under the same heating conditions.

[0052] 3. The reading of the electronic depth vernier caliper in this teaching aid will gradually increase as the heating time of the long strip of metal increases, which can intuitively reflect the gradual process of metal expansion.

[0053] 4. Using this teaching aid, students can quantitatively observe the length of metal expansion and measure the expansion length accurately to 0.01mm.

[0054] This experimental teaching aid uses the principle of "magnification" to make the difficult-to-observe thermal expansion and contraction of metal easier to observe, and even to display it quantitatively. This teaching aid mainly achieves the following three "magnifications", which are the core of the design of this utility model:

[0055] 1. The first enlargement of the teaching aids

[0056] When metal is heated, it will generally expand freely in all directions, and it is difficult to measure the actual change value of the metal. In this experiment, one end of the metal is fixed, and the other end is allowed to expand freely after being heated, so that the expansion change of the metal at both ends is concentrated to one end (the free end), achieving the first amplification.

[0057] 2. Second enlargement of teaching aids

[0058] When metal expands due to heat, its volume increases as a whole. In order to more intuitively observe the changes in metal expansion and contraction and amplify the changes in metal expansion, this experiment selected a long strip of metal (about 25cm in length and 4-5mm in thickness) as the experimental object, and took the change in its longitudinal length (25cm in the direction of length change) as the observation object to achieve the accumulation and amplification of the expansion length, making it easier to observe the change in length and achieve a second amplification.

[0059] 3. The third enlargement of teaching aids

[0060] This teaching aid uses the magnification measurement principle of the electronic vernier caliper to measure the change in the length of a long metal strip before and after heating, thus achieving the third magnification.

[0061] 1. The utility model uses one end of the fixed metal, while the other end can expand and extend freely after being heated, so as to concentrate the expansion change of the metal to both ends to one end (free end), thus realizing the amplification of the first expansion; uses the long strip of metal to amplify the accumulated expansion length due to heat, thus realizing the amplification of the second expansion; uses the amplification measurement principle of the electronic vernier caliper to measure the specific change of the length of the long strip of metal before and after being heated, thus realizing the third amplification. After three amplifications, the electronic vernier caliper can accurately measure the length change of the metal expansion due to heat.

[0062] 2. Traditional teaching aids can only qualitatively observe the expansion of the copper ball when heated and the contraction when cooled, but cannot quantitatively observe the change in length of the metal when heated and the change in length when cooled. The utility model can quantitatively observe the change in length of the metal when heated and the change in length when cooled, and the length change can be accurately calculated to 0.01mm.

[0063] 3. Traditional teaching aids can only qualitatively observe the expansion and contraction of one metal (copper ball) when heated and when cooled, and cannot compare the degree of thermal expansion and contraction of different metals. The utility model can simultaneously measure the thermal expansion and contraction properties of two metals, and intuitively display the difference in the expansion and contraction properties of the two metals. The difference in expansion and contraction properties includes the speed (speed), degree (length), and ratio of expansion under the same heating conditions.

[0064] 4. Traditional teaching aids cannot observe the gradual process of metal expansion due to heat. In the utility model, the reading of the electronic depth vernier caliper will gradually increase as the heating time of the long strip of metal becomes longer, so the gradual process of metal expansion can be observed intuitively.

Claims

1. A teaching aid for quantitatively comparing the thermal expansion and contraction of different metals, characterized in that: include: Base (1), electronic depth vernier caliper, L-shaped steel plate (8) and long metal strip; An L-shaped steel plate is fixed to one end of the base (1), and at least two parallel long metal strips are arranged above the base (1). The left side of the long metal strip abuts against the L-shaped steel plate (8), that is, the contact position between the left end of the long metal strip and the L-shaped steel plate (8) is the fixed end of the long metal strip; the right end of the long metal strip is a free end that expands due to heat, and the free end is connected to an electronic depth vernier caliper, and the number of the long metal strip and the electronic depth vernier caliper is the same; A plurality of identical heat sources are placed under the long metal strip, with one heat source being placed under each long metal strip.

2. A teaching aid for quantitatively comparing the degree of thermal expansion and contraction of different metals according to claim 1, characterized in that: The long strip of metal is placed on top of the steel spacer (9).

3. A teaching aid for quantitatively comparing the degree of thermal expansion and contraction of different metals according to claim 1, characterized in that: The base section is set to be concave.

4. A teaching aid for quantitatively comparing the thermal expansion and contraction of different metals according to claim 1, characterized in that: The size of the long metal strip is 25cm×1cm×0.2cm.

5. A teaching aid for quantitatively comparing the thermal expansion and contraction of different metals according to claim 1, characterized in that: There are two long metal strips and two electronic depth vernier calipers.

6. A teaching aid for quantitatively comparing the thermal expansion and contraction of different metals according to claim 1, characterized in that: The heat source is a double-head alcohol lamp (4) or two identical alcohol lamps.

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