CN108682247B - Experimental instrument for demonstrating stress of copper bar in magnetic field and quantitatively measuring copper bar - Google Patents

Abstract

The invention relates to an experimental instrument for demonstrating and quantitatively measuring stress of a copper bar in a magnetic field, which comprises an electric cabinet, an experimental instrument base, a photoelectric sensor fixing longitudinal beam, a copper bar track supporting rod, a correlation photoelectric sensing receiver supporting rod, a copper bar guide rail, a rectangular large coil, an electrified copper bar and a conductive rectangular light blocking copper sheet, wherein the electric cabinet is provided with a plurality of light blocking copper sheets; the experimental instrument base is formed by interconnecting front and rear longitudinal beams and left and right cross beams, and the lower end of the experimental instrument base is provided with base leveling supporting legs; the left support rod of the correlation photoelectric sensing receiver and the right support rod of the correlation photoelectric sensing receiver are respectively fixed at the center positions of the left and right cross beams of the base of the experimental instrument. The beneficial effects of the invention are as follows: the invention adopts the electric cabinet constant current source to provide the coil with the changed current so as to generate the changed magnetic field, the current of the constant current source can be displayed by the display screen, and the change of the current and the direction can be realized by providing the coil with the current direction and the size increasing and decreasing knob by the constant current source with special functions.

Description

An experimental instrument for demonstrating and quantitatively measuring the force of a copper rod in a magnetic field

Technical field

The invention belongs to the technical field of physics experimental devices, and specifically relates to an experimental instrument for demonstrating and quantitatively measuring the force of a copper rod in a magnetic field.

Background technique

In middle school physics teaching, a current-carrying wire will be affected by a magnetic field force in a magnetic field. The direction of this force is judged according to the left-hand rule. The size of the force is proportional to the strength of the magnetic field, the current passing through the wire, and the current flowing through the wire. is directly proportional to the length, which can be expressed by the formula F=BIL. This knowledge point is a very important content in middle school teaching. However, for students who have just entered middle school, it is the first time for students to come into contact with this part of the content and get involved in these concepts. It is generally difficult to understand, and even more difficult to use flexibly and fully master in a short period of time. According to the teaching rules of physics, in order for students to quickly master and practice it skillfully, in addition to the teacher's explanation and a large number of corresponding questions, in fact, a very critical aspect is that the teacher needs to demonstrate the physical phenomenon and let the students observe or personally Demonstrate and observe by hands-on, and then deepen the understanding of this concept, truly realize that the magnetic field force on the current-carrying wire is indeed proportional to the three physical quantities B, I, and L, and judge the direction of the force on the current-carrying wire by using the left-hand rule. correctness.

At present, in middle school physics teaching, there are only a few types of physical experimental instruments used. First, a horseshoe-shaped magnet is used to provide a magnetic field. Copper rods are suspended with copper wires at both ends, and the angle of the copper rod is swung A self-made experimental demonstration instrument to demonstrate the magnitude of the force; secondly, the energized copper rod is also placed in the magnetic field provided by the horseshoe magnet. A copper rod is placed on a guide rail using two copper rods as guide rails. Observe the copper rod. A self-made demonstration experimental device that uses the speed at which the rod is accelerated to determine the magnitude of the force. Throughout these experimental instruments, they all demonstrate qualitatively, or can only change the direction of the current, and there are many disadvantages, such as: first, the size and direction of the magnetic field cannot be changed, and the magnetic field cannot change continuously; second, the experimental guide rail Generally, the width is fixed, and it is difficult to demonstrate changing the length of the energized copper rod, or although the length of the energized copper rod can be changed, the structure of the experimental instrument is not very ideal, the experiment is inaccurate, and the operation is not convenient; thirdly, these experimental instruments Generally, it can only demonstrate qualitative experiments, and it is impossible to conduct quantitative experiments at all, or even more unable to demonstrate multiple quantitative experiments; fourth, it is impossible to measure the instantaneous speed of a energized copper rod at a certain position in the magnetic field, and the acceleration of a certain period of motion; fifth , it is impossible to measure the size of the average magnetic field of the energized coil; sixth, it is impossible to qualitatively measure the magnitude of the induced electromotive force generated on the copper rod during the movement of the energized copper rod.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art and provide an experimental instrument for demonstrating and quantitatively measuring the force of a copper rod in a magnetic field.

This experimental instrument for demonstrating and quantitatively measuring the force of a copper rod in a magnetic field includes an electric control box, an experimental instrument base, a photoelectric sensor fixed longitudinal beam, a copper rod track support rod, a through-beam photoelectric sensor receiver support rod, and a copper rod. Guide rails, large rectangular coils, conductive copper rods and conductive rectangular light-blocking copper sheets;

The base of the experimental instrument is composed of front and rear longitudinal beams and left and right cross beams connected to each other. The lower end of the experimental instrument base is equipped with base leveling support legs; the left support rod of the through-beam photoelectric sensor receiver and the right support rod of the through-beam photoelectric sensor receiver are respectively The center position of the left and right cross beams fixed on the base of the experimental instrument; the left and right support rods of the through-beam photoelectric sensor correspond to the left and right cross beams of the base of the lower end frame, and a lower photoelectric sensor transmitter fixed longitudinal beam is set in the middle, and the upper ends of the left and right support rods of the through-beam photoelectric sensor are set There is an upper photoelectric sensor receiver fixed on the longitudinal beam; the first through-beam photoelectric sensor transmitter and the second through-beam photoelectric sensor transmitter are fixed at the corresponding positions of the lower photoelectric sensor transmitter fixed longitudinal beam, and the two The connecting wires of the first through-beam photoelectric sensor transmitter and the second through-beam photoelectric sensor transmitter are respectively connected to the corresponding terminals of the electric control box; the first through-beam photoelectric sensor receiver and the second pair The radial photoelectric sensor receiver is fixed at the corresponding position of the upper photoelectric sensor receiver fixed longitudinal beam, and the first through-beam photoelectric sensor receiver connecting wire and the second through-beam photoelectric sensor receiver are connected The wires are connected to the corresponding terminal posts of the electric control box;

The large rectangular coil is placed in the middle of the base of the experimental instrument. The incoming coil current connecting wires and the outgoing coil current connecting wires of the rectangular large coil are respectively connected to the corresponding terminals of the electric control box; the left support rod of the front copper rod track and the left support of the rear copper rod track The supporting feet of the rod are respectively fixed on the front and rear ends of the left crossbeam of the experimental instrument base and at corresponding positions symmetrical with respect to the center of the left crossbeam. The supporting feet of the right supporting rod of the front copper rod track and the right supporting rod of the rear copper rod track are respectively fixed on the right side of the experimental instrument base. The front and rear ends of the crossbeam are in corresponding positions that are symmetrical about the center of the right crossbeam; the front copper rod guide rail and the rear copper rod guide rail are respectively installed on the corresponding sets of columns corresponding to the upper ends of the left and right support rods of the front copper rod track and the left and right support rods of the rear copper rod track. The copper rod guide rails are close to the upper surface of the large rectangular coil and are on the same plane; energized copper rods are placed vertically on the front copper rod guide rail and the rear copper rod guide rail, and the energized copper rods are equipped with conductive rectangular light-blocking copper sheets; the front copper rod The guide rail and the rear copper rod guide rail are respectively connected to the corresponding terminal posts of the electric control box through the front copper rod guide rail connecting wire and the rear copper rod guide rail connecting wire.

As a preferred option: the support feet of the left support rod of the through-beam photoelectric sensor receiver are moved from the front and rear copper rod guide rail support feet of the left beam of the experimental instrument base to the center of the left beam, and the through-beam photoelectric sensor receiver The right support rod of the instrument is moved from the front and rear copper rod guide rail support feet of the right crossbeam of the experimental instrument base to the center of the right crossbeam. The two support rods are fixed with fixing screws respectively.

As a preferred option: the support legs of the left support rod of the front copper rod track and the left support rod of the rear copper rod track are respectively inserted into the left crossbeam from the front and rear copper rod guide rail support foot moving slides of the left crossbeam of the experimental instrument base and are symmetrical about the center of the left crossbeam. The two support rods are fixed with fixing screws at the corresponding positions. The center distance between the left support rod of the front copper rod track and the left support rod of the rear copper rod track is the effective length L value of the energized copper rod; the right support rod of the front copper rod track and the rear copper rod The support feet of the right support rod of the rod track are inserted into the right cross beam from the front and rear copper rod guide rail support foot moving slides of the right cross beam of the experimental instrument base and are symmetrical about the center of the right cross beam. The two support rods are fixed with fixing screws. The center distance between the right support rod of the copper rod track and the right support rod of the rear copper rod track is the effective length L value of the energized copper rod.

As a preferred option: the front copper rod guide rail and the rear copper rod guide rail are respectively installed on the corresponding sets of columns corresponding to the upper ends of the left and right support rods of the front copper rod track and the left and right support rods of the rear copper rod track and fixed with fixing screws.

As a preferred option: the two fixed ferrules on the left and right of the upper photoelectric sensor receiver fixed longitudinal beam are respectively placed on the sleeve posts at the top of the left support rod of the through-beam photoelectric sensor receiver and the right support rod of the through-beam photoelectric sensor receiver. And fixed by fixing screws.

As a preferred method: the scale on which the upper photoelectric sensor receiver fixes the longitudinal beam corresponds to the scale on which the lower photoelectric sensor transmitter fixes the longitudinal beam. The first through-beam photoelectric sensor receiver and the second through-beam photoelectric sensor receiver The scale position of the sensing receiver corresponds to the scale position of the first through-beam photoelectric sensor transmitter and the second through-beam photoelectric sensor transmitter respectively.

As a preferred option: the electric control box includes an electric control box power switch, an electric control box indicator light, a through-beam photoelectric sensing time display switch, a through-beam photoelectric sensing time display screen, and a constant current source that provides the coil with current direction and size increase. Decrease knob, constant current source current size display and constant current source provide current direction and size increase and decrease knobs for the energized copper rod.

The beneficial effects of the present invention are:

1. The present invention uses a constant current source in an electric control box to provide changing current to the coil to generate a changing magnetic field. The current size of the constant current source can be displayed through the display screen. Changes in the current size and direction can be displayed through a special function. The constant current source provides the current direction and size increase and decrease knob for the coil to achieve this. That is, the button is turned up to provide forward current to the coil, and pressed down to provide reverse current to the coil. Regardless of providing forward current or reverse current, the knob clockwise The rotational current continues to increase, and the counterclockwise rotational current continues to decrease, which provides convenience for verifying the left-hand rule to determine the direction of the force.

2. The distance between the front copper rod guide rail and the rear copper rod guide rail can be changed symmetrically about the center of the left and right crossbeams of the base. The support rod feet can change the distance between the energized copper rod guide rails by sliding in the chute. The exact distance between the front and rear copper rod guide rails can be Read on the millimeter scale on the left and right beams of the base.

3. This experimental instrument uses two through-beam photoelectric sensors, which can measure the instantaneous speed of the energized copper rod passing through the two through-beam photoelectric sensors, and calculate the acceleration of the energized copper rod's movement based on the distance between the two sensors. , so that the average magnetic field size generated by the energized coil and the force of the energized copper rod in the magnetic field can be calculated.

4. The experimental device uses an electric control box. The electric control box contains a constant current source that provides the direction and magnitude of current for the coil and a constant current source that provides the direction and magnitude of current for the energized copper rod. The current is provided for the copper rod through The ingenious power transmission of the guide rail avoids the mutual entanglement of wires that would be caused by directly connecting the wires to both ends of the copper rod; at the same time, the electric control box is also equipped with a photoelectric display to promptly display the power of the through-beam sensor due to the energized rectangular sheet. The occlusion time of the received light provides a time parameter for calculating the instantaneous speed of the copper rod passing through the through-beam photoelectric sensor.

5. This experimental instrument can be used for both demonstration experiments and quantitative experiments. Through quantitative experiments, it can measure the force exerted by the energized copper rod in the magnetic field, the average magnetic field strength generated by the coil current, and the uniform motion of the energized copper rod. The magnitude of the induced electromotive force generated by the magnetic field.

6. Be able to demonstrate the relationship between the force in the formula F = BIL and the physical quantities on the right side of the equation: First, when the current I and length L remain unchanged, as the magnetic field B increases, the force increases. When the direction of the magnetic field changes, When the direction of the force on the energized copper rod is opposite; second, when the magnetic field B and current L remain unchanged, the current I increases and the force increases; when the direction of the current changes, the force direction is opposite; third, when the magnetic field B. When the current I remains unchanged, changing the length L of the energized copper rod will cause the force to change. When the length L of the energized copper rod increases, the force increases. When the length L decreases, the force decreases.

7. This experimental instrument has an ingenious design and reasonable structure. It is a comprehensive experimental instrument.

Description of the drawings

Figure 1 is a front view of the overall structure of the experimental instrument of the present invention;

Figure 2 is a right view of the structure of the leveling support legs, base, coil, support rod and photoelectric sensor;

Figure 3 is a top view of the overall structure of the experimental instrument of the present invention;

Figure 4 is a top view of the base, support rods, photoelectric sensors and fixed longitudinal beams;

Figure 5 is an enlarged top view of the base support legs, left and right cross beams, photoelectric sensor support rods, chute, scale, etc.;

Figure 6 is a structural top view of the upper photoelectric sensor, fixed longitudinal beam and fixed ferrule;

Figure 7 is a structural top view of the front and rear copper rod guide rails and fixed ferrules;

Figure 8 is a schematic structural diagram of the copper rod track support rod and the through-beam photoelectric sensor receiver support rod (a is the structural schematic diagram of the copper rod track support rod, b is the structural schematic diagram of the through-beam photoelectric sensor receiver support rod) ;

Figure 9 is a structural top view of the energized copper rod (including the middle conductive rectangular light-blocking copper sheet);

Figure 10 is a schematic diagram of the copper rod track, copper rods, photoelectric sensor fixed longitudinal beams and connections;

Figure 11 is a structural front view of the electric control box.

Explanation of reference signs: 1. Electric control box, 1-0. Electric control box power switch, 1-1. Electric control box indicator light, 1-2. Through-beam photoelectric sensing time display switch, 1-3. Right Radial photoelectric sensing time display, 1-4. The constant current source provides the current direction and size increase and decrease knob for the coil, 1-5. The constant current source current size display, 1-6. The constant current source is an energized copper rod. Provides current direction and size increase and decrease knobs, 2. Experimental instrument base, 2-0, base leveling support legs, 2-00, front and rear copper rod guide rail support feet moving slides, 2-1, base left beam ruler, 2- 2. Scale of the right beam of the base, 2-10, chute section, 3. Lower photoelectric sensor transmitter fixed longitudinal beam, 3-1, first through-beam photoelectric sensor transmitter, 3-2, second through-beam type photoelectric sensing transmitter, 3-10. Connect the wire to the first through-beam photoelectric sensing transmitter, 3-20. Connect the wire to the second through-beam photoelectric sensing transmitter, 4. Fix the upper photoelectric sensing receiver Longitudinal beam, 4-00, upper photoelectric sensor receiver fixed longitudinal beam fixed ferrule, 4-1, first through-beam photoelectric sensor receiver, 4-2, second through-beam photoelectric sensor receiver, 4-10. The connecting wire of the first through-beam photoelectric sensing receiver, 4-20. The connecting wire of the second through-beaming photoelectric sensing receiver, 5-1. The left support rod of the front copper rod track, 5-01. Front copper rod track left support rod foot, 5-02, front copper rod track left support rod foot fixing screw, 5-04, front and rear copper rod guide rail fixing ferrule sleeve column, 5-05, front and rear copper rod track fixing ferrule fixing screws , 5-10, rear copper rod track left support rod, 5-11, rear copper rod track left support rod foot, 5-12, rear copper rod track left support rod foot fixing screw, 5-2, front copper rod track right Support rod, 5-20, rear copper rod track right support rod, 5-21, front copper rod track right support rod foot, 5-22, front copper rod track right support rod foot fixing screw, 5-25, rear copper rod Track right support pole foot, 5-26, rear copper rod track right support pole foot fixing screw, 6-1, through-beam photoelectric sensor receiver left support rod, 6-11, through-beam photoelectric sensor receiver fixation The left support leg of the longitudinal beam, 6-12. The through-beam photoelectric sensor receiver is fixed to the left support leg of the longitudinal beam. The fixing screw is 6-05. The upper photoelectric sensor receiver is fixed to the longitudinal beam and the collar is fixed to the column. 6-06 , the upper photoelectric sensor receiver fixes the longitudinal beam and fixes the ferrule fixing screw, 6-2, the through-beam photoelectric sensor receiver right support rod, 6-21, the through-beam photoelectric sensor receiver fixes the longitudinal beam right support rod Feet, 6-22, through-beam photoelectric sensor receiver fixing longitudinal beam right support rod foot fixing screw, 7-1, front copper rod guide rail, 7-2, rear copper rod guide rail, 7-00, front and rear copper rod guide rail Fixed ferrule, 7-10, front copper rod guide rail connection wire, 7-20, rear copper rod guide rail connection wire, 8, rectangular large coil, 8-1, inflow coil current connection wire, 8-2, outflow coil current connection connection Wire, 10, energized copper rod, 10-0, conductive rectangular light-blocking copper sheet.

Detailed ways

The present invention will be further described below in conjunction with examples. The following description of the examples is provided only to assist understanding of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of the claims of the present invention.

The described experimental instrument for demonstration and quantitative measurement of copper rod stress in a magnetic field includes: electric control box 1, experimental instrument base 2, photoelectric sensor fixed longitudinal beam, copper rod track support rod, through-beam photoelectric sensor receiver support Rod, copper rod guide rail, rectangular large coil 8, energized copper rod 10, conductive rectangular light-blocking copper sheet 10-0, as shown in Figure 1.

Install the four base leveling support legs 2-0 at the lower end of the experimental instrument base 2. The experimental instrument base 2 is cleverly connected to each other by the front and rear longitudinal beams and the left and right cross beams to form a quadrilateral. Use the base leveling support legs 2-0 to secure the experimental instrument base. 2. Adjust it to level (use a spirit level to check); insert the supporting legs of the left support rod 6-1 of the through-reflective photoelectric sensor receiver from the left crossbeam slide of the experimental instrument base 2 to the center of the left crossbeam. The support legs of the right support rod 6-2 of the through-beam photoelectric sensor receiver are inserted from the right beam slide of the experimental instrument base 2 to the center of the right beam, and are fixed tightly with fixing screws, as shown in Figures 1, 2, and 3. shown.

According to the spacing and position requirements of the first through-beam photoelectric sensor transmitter 3-1 and the second through-beam photoelectric sensor transmitter 3-2, connect the first through-beam photoelectric sensor transmitter 3-1 and the second through-beam photoelectric sensor transmitter 3-1. The two through-beam photoelectric sensor transmitters 3-2 are fixed at the corresponding positions of the lower photoelectric sensor transmitter fixed longitudinal beam 3 (remember the corresponding scale values), and connect the first through-beam photoelectric sensor transmitter of the two The wire 3-10 and the second through-beam photoelectric sensor transmitter connecting wire 3-20 are respectively connected to the corresponding terminals of the electric control box 1, as shown in Figures 4, 3, and 1.

Place the large rectangular coil 8 at the corresponding position on the base 2 of the experimental instrument, and connect the incoming coil current connecting wire 8-1 and the outgoing coil current connecting wire 8-2 of the rectangular large coil 8 to the corresponding terminal posts of the electric control box 1 respectively. on so that the constant current source of the electric control box supplies power to the coil to generate a magnetic field, as shown in Figures 2, 3, and 1.

Insert the support legs of the front copper rod track left support rod 5-1 and the rear copper rod track left support rod 5-10 from the front and rear chute of the left crossbeam of the experimental instrument base 2 into the left crossbeam chute and about the center of the left crossbeam. Symmetrically corresponding positions, so that the center distance between the left support rod 5-1 of the previous copper rod track and the left support rod 5-10 of the rear copper rod track (the accurate distance can be obtained from the scale) is the effective distance of the energized copper rod required for the experiment. Length L value, and secure the left support rod 5-1 of the front copper rod track and the left support rod 5-10 of the rear copper rod track with fixing screws; then secure the right support rod 5-2 of the front copper rod track with the rear copper rod The support legs of the track right support rod 5-20 are inserted into the right beam chute from the front and rear chute of the right crossbeam of the experimental instrument base 2 and at corresponding positions symmetrical about the center, so that the previous copper rod track right support rod 5-2 and The center distance between the right support rod 5-20 of the rear copper rod track (the accurate distance can be obtained from the scale) is the effective length L value of the energized copper rod required for the experiment. Place the right support rod 5-2 of the copper rod track and the rear copper rod The right support rods 5-20 of the track are tightened with fixing screws respectively, as shown in Figures 2, 3, 4, 5, 8 and 1.

Then install the front copper rod guide rail 7-1 and the rear copper rod guide rail 7-2 respectively on the corresponding sets of columns corresponding to the upper ends of the left and right support rods of the front copper rod track and the left and right support rods of the rear copper rod track. The front and rear copper rod guide rails are both tight. Attach the upper surface of the large rectangular coil 8 to the same plane, and use fixing screws to fix them one by one; place the energized copper rod 10 vertically on the front copper rod guide rail 7-1 and the rear copper rod guide rail 7-2. 10 is provided with a conductive rectangular light-blocking copper sheet in the middle; the front copper rod guide rail 7-1 and the rear copper rod guide rail 7-2 are respectively connected to the front copper rod guide rail connecting wire 7-10 and the rear copper rod guide rail connecting wire 7-20. On the corresponding terminal of the electric control box 1, the sliding copper rod connected to the copper rod guide rail is powered through the constant current source of the electric control box, as shown in Figures 3, 2, 1, 7, 9, and 10.

Place the left and right fixing rings of the upper photoelectric sensor receiver fixed longitudinal beam 4 on the left support rod 6-1 of the through-beam photoelectric sensor receiver and the right support rod 6-2 of the through-beam photoelectric sensor receiver. On the top sleeve column, fixing screws are used to fix it; the scale of the upper photoelectric sensor receiver fixed longitudinal beam 4 corresponds to the scale of the lower photoelectric sensor transmitter fixed longitudinal beam 3. According to the first alignment The scale positions of the through-beam photoelectric sensor transmitter 3-1 and the second through-beam photoelectric sensor transmitter 3-2 are the first through-beam photoelectric sensor receiver 4-1 and the second through-beam photoelectric sensor receiver 4-1. 4-2 is fixed correspondingly; the first through-beam photoelectric sensor transmitter connecting wire 3-10 and the second through-beam photoelectric sensor transmitter connecting wire 3-20 drawn from the electric control box 1 are respectively connected with the first pair The through-beam photoelectric sensor transmitter 3-1 is connected to the second through-beam photoelectric sensor transmitter 3-2, and the first through-beam photoelectric sensor receiver connected from the electric control box 1 is connected to the wire 4-10. The two through-beam photoelectric sensor receiver connecting wires 4-20 are respectively connected to the first through-beam photoelectric sensor receiver 4-1 and the second through-beam photoelectric sensor receiver 4-2, so that the first pair The light emitted by the through-beam photoelectric sensor emitter 3-1 and the second through-beam photoelectric sensor emitter 3-2 can just be absorbed by the first through-beam photoelectric sensor receiver 4-1 and the second through-beam photoelectric sensor receiver 4-1. The sensor receiver 4-2 receives correspondingly; the light emitted by the first through-beam photoelectric sensor transmitter 3-1 and the second through-beam photoelectric sensor transmitter 3-2 is blocked by the conductive rectangular light-blocking copper sheet 10-0 Light blocking and light blocking information are respectively received by the first through-beam photoelectric sensor receiver 4-1 and the second through-beam photoelectric sensor receiver 4-2, which are respectively connected by the first through-beam photoelectric sensor receiver. The wire 4-10 is connected to the second through-beam photoelectric sensor receiver and the wire 4-20 is transmitted to the electric control box 1, thereby displaying the light blocking time on the display screen to provide calculation of the movement speed of the energized copper rod passing through the predetermined position. , as shown in Figures 6, 10, 9, 8, 5, 4, 3, 2, and 1.

1. Structure and principle of special parts of this experimental instrument

1. Production of energized copper rods. An electrified rectangular thin copper sheet of reasonable size is used in the middle of the energized copper rod. The copper rod and the thin copper sheet are connected and conductive. The cross-sectional area of the thin copper sheet is required to be equal to the cross-sectional area of the copper rod. The thin copper sheet acts as a barrier to the through-beam photoelectric sensor. Due to the effect of light, the width of the thin copper sheet can be measured using a vernier caliper. According to the light blocking time displayed on the photoelectric display screen of the electric control box, the instantaneous speed of the energized copper rod moving to the position of the photoelectric sensor can be calculated.

2. The size of the rectangular coil and the number of winding turns are determined according to the needs of specific experiments and are specifically produced and wound.

3. Constant current source function of the electric control box. This constant current source current size display can simultaneously display the constant current source current provided to the energized copper rod and provide current to the coil. Among them, the constant current source provides the direction and size of the current to the coil. The increase and decrease knobs 1-4 are multi-purpose knobs. When they are turned up, they provide forward current to the coil, and when pressed down, they provide reverse current to the coil, regardless of whether they provide forward current or reverse. Current, when turning the knob clockwise, the current will increase, and when turning the knob counterclockwise, the current will decrease; the constant current source provides the current direction and size for the energized copper rod. The increase and decrease knobs 1-6 pop up to provide forward current for the copper rod, and push down to provide forward current for the copper rod. The copper rod provides reverse current. Whether it provides forward current or reverse current, the current increases when rotated clockwise and decreases when rotated counterclockwise.

4. The fluorescent screen display function of the photoelectric sensor of the electric control box. As long as it complies with the light blocking principle of the two through-beam photoelectric sensors, the photoelectric sensor display screen will sequentially display the time when the two through-beam photoelectric sensors are blocked. The photoelectric sensor The display switch plays the role of clearing. If the fluorescent screen displays again, just press the button to clear it. The light blocking time of the copper rod passing through the two photoelectric sensors will continue to be displayed next time.

5. A coil that provides a magnetic field for the experiment. The coil used in this experimental instrument is a special rectangular coil that is very similar to the base of the experimental instrument. The height of the coil is appropriate, and the width of the coil is the same as the width of the base of the experimental instrument; the length of the coil needs to be determined according to the power supply The copper rod is accelerated by the force of the magnetic field, and it is better to eventually reach a uniform speed and last for a certain distance to determine the length of the coil; the number of turns of the coil is wound according to the specific requirements of the magnetic field size required by the experimental instrument, and the coil current Provided by a constant current source in the electric control box, the coil current can increase and decrease in sequence, so that the coil can produce a changing magnetic field.

6. Through-beam photoelectric sensor module. The through-beam photoelectric sensor consists of three parts: the transmitter, the receiver and the detection circuit. The laser diode is used as the transmitter, emitting red light, and the receiver is a photodiode. The distance between the transmitter and the receiver can be 1m or even several meters. The front side of the receiver is equipped with an optical element aperture, and the back of the receiver uses a detection A circuit that filters out valid signals and applies that signal. When an object passes between the transmitter and the receiver, the light is cut off, and the receiving end outputs a signal.

7. It should be emphasized that the base of the experimental instrument, the support rod, the coil winding frame and the fixing screws are all made of plastic materials, so that the structure composed of these materials will not affect the magnetic field generated by the energized coil; in addition, the rectangular coil The width is almost the same as the width of the base. The maximum width of the guide rail spacing should be less than or equal to the inner width of the coil. However, the coil length should be determined according to the needs of the test conditions during the manufacturing process of the experimental instrument. The coil length can be longer than the currently designed length, or even The guide rail support rod and the through-beam photoelectric sensor support rod can be included inside the coil length, which may have better experimental results using this experimental instrument.

2. Experimental principles and methods of this experimental instrument

1. Demonstration experiments (including demonstrating the correctness of the left-hand rule)

Theoretical calculation formula for the force exerted on an energized copper rod in a magnetic field

F＝BIL……(1)

In the formula, B represents the magnetic induction intensity, I represents the energizing current, and L represents the length of the energized copper rod in the magnetic field.

(1) Keep the constant current source current I provided by the copper rod and the length L of the copper rod (adjust the distance between the front and rear copper rod guide rail support legs) unchanged, and increase the current provided by the constant current source to the coil (the constant current source provides the current direction for the coil Rotate the size increase and decrease knobs 1-4 clockwise), that is, the magnetic field B generated by the coil increases, the force on the energized copper rod increases, and the copper rod moves faster; if the direction of the magnetic field is opposite (the constant current source provides the current direction for the coil Press down the size increase and decrease knobs 1-4), and the copper rod will move in the opposite direction to the original;

(2) Keep the size of the magnetic field (i.e., the size of the coil current) B and the length of the energized copper rod (i.e., the distance between the front and rear copper rod guide rail support rods) L unchanged. When the current (constant current source) provides the current direction and size increase and decrease knob for the energized copper rod 1-6 Rotate clockwise) I increases, the force of the energized copper rod increases, and the copper rod moves faster; if the current direction is opposite (the constant current source provides the current direction and size for the energized copper rod, press down the increase and decrease knob 1-6 ), the copper rod moves in the opposite direction to its original motion;

(3) Keep the size of the magnetic field (i.e., the size of the coil current) B and the constant current source current I provided by the copper rod unchanged. In the magnetic field, the length of the energized wire (i.e., the distance between the front and rear copper rod track support rods) L increases, and the acting force increases, the copper rod moves faster;

2. Measure the movement speed, acceleration and force of the copper rod

Since the energized copper rod starts to move slowly, two through-beam photoelectric sensors are fixed at a suitable position at the starting end of the movement of the copper rod at a certain distance. The light blocking time of the two through-beam photoelectric sensors is measured as Δt ₁ and Δt ₂ , and the light-blocking width ΔL of the energized rectangular copper sheet is measured, then the speed of the energized first copper rod passing through the through-beam photoelectric sensor and the second through-beam photoelectric sensor are v ₁ = ΔL/Δt ₁ , v ₂ =ΔL/Δt ₂ , and the distance between the first through-beam photoelectric sensor and the second through-beam photoelectric sensor is s, according to the speed and distance relationship formula Then the acceleration of the movement of the copper rod/> Assume the mass of the copper rod is m. For the convenience of calculation, if the magnitude of the induced electromotive force is negligible, according to Newton's second law: Ff=ma, assuming the friction coefficient μ between the copper rod and the copper rod guide rail, then the copper rod is in the copper rod track The friction force f=μmg on the energized copper rod, then the force exerted by the energized copper rod in the magnetic field is F=μmg+ma. Then it can be measured that the average magnetic field generated by the energized coil current is:

3. Measure the induced electromotive force (this experiment is an extended experiment and its feasibility needs to be further studied. Here is just a research idea)

When a moving copper rod (conductor) moves in a magnetic field, it will generate an induced electromotive force. The direction of the induced electromotive force can be judged by the right-hand rule. The magnitude of the induced electromotive force can be calculated by the following formula

ε＝BLv……(3)

Since the energized copper rod moves under the action of the magnetic field force in the magnetic field, the copper rod will be affected by three forces in the direction of movement during the movement, the action force, the friction force, the induced electromotive force generated on the copper rod and the copper The induced current generated by the rod resistance will also be subject to a force. When the copper rod reaches balance under the action of these three forces, that is, when the copper rod movement speed reaches a uniform speed, the two through-beam photoelectric sensors can be separated by a certain distance, respectively. Correspondingly fixed near the end, this will facilitate the movement of the copper rod to reach uniform motion, and then measure the movement speed of the copper rod. Suppose the resistance of the effective length L of the energized copper rod is R. Since the cross-sectional area of the rectangular sheet energized in the middle is s ₀ is the same as the cross-sectional area of the circular copper rod, then according to the resistance law, the resistance of the copper rod with length L The induced current i=ε/r=BLvs ₀ /ρL generated by the induced electromotive force on the copper rod is the same as the direction of the induced current, which is the same as the direction of the current provided by the constant current source to the copper rod. On the contrary, the current on the copper rod is Ii at this time. According to the force of the combined current on the copper rod in the magnetic field, it should be balanced with the resistance of the copper rod, that is, F = f, then there is

B(I-Bvs ₀ /ρ)L=μmg……(4)

According to equation (4), the average magnetic field B generated by the energized coil can be calculated, and then according to (3), the magnitude of the induced electromotive force generated by the energized copper rod in the magnetic field can be calculated; or based on some physical quantities, another one can also be calculated physical quantity.

Claims (7)

1. An experimental instrument for demonstrating and quantitatively measuring the force of a copper rod in a magnetic field, which is characterized by: including an electric control box (1), an experimental instrument base (2), a photoelectric sensor fixed longitudinal beam, a copper rod track support rod, and a pair of Radial photoelectric sensor receiver support rod, copper rod guide rail, rectangular large coil (8), energized copper rod (10) and conductive rectangular light-blocking copper sheet (10-0); The experimental instrument base (2) is composed of front and rear longitudinal beams and left and right cross beams connected to each other. The lower end of the experimental instrument base (2) is provided with a base leveling support leg (2-0); the through-beam photoelectric sensor receiver left support rod (6 -1) and the right support rod (6-2) of the through-beam photoelectric sensor receiver are respectively fixed at the center of the left and right beams of the experimental instrument base (2); the left and right support rods of the through-beam photoelectric sensor correspond to the left and right sides of the base of the lower end frame A lower photoelectric sensing transmitter fixed longitudinal beam (3) is provided in the middle of the beam, and an upper photoelectric sensing receiver fixed longitudinal beam (4) is provided at the upper end of the left and right support rods of the through-beam photoelectric sensor; the first through-beam photoelectric sensor transmitter The transmitter (3-1) and the second through-beam photoelectric sensor transmitter (3-2) are fixed at the corresponding positions of the fixed longitudinal beam (3) of the lower photoelectric sensor transmitter, and the first through-beam photoelectric sensor transmitter of the two is The sensor-emitter connecting wire (3-10) and the second through-beam photoelectric sensor-emitter connecting wire (3-20) are respectively connected to the corresponding terminals of the electric control box (1); the first through-beam photoelectric sensor The receiver (4-1) and the second through-beam photoelectric sensing receiver (4-2) are fixed at the corresponding positions of the upper photoelectric sensing receiver fixed longitudinal beam (4), and the first through-beam type of the two The photoelectric sensor receiver connecting wire (4-10) and the second through-beam photoelectric sensor receiver connecting wire (4-20) are respectively connected to the corresponding terminal posts of the electric control box (1); The large rectangular coil (8) is placed in the middle of the experimental instrument base (2). The inflow coil current connection wire (8-1) and the outflow coil current connection wire (8-2) of the rectangular large coil (8) are connected to the electric control box respectively. (1) On the corresponding terminal; the support legs of the front copper rod track left support rod (5-1) and the rear copper rod track left support rod (5-10) are respectively fixed on the front and rear ends of the left crossbeam of the experimental instrument base (2) And at corresponding positions that are symmetrical about the center of the left crossbeam, the support feet of the right support rod of the front copper rod track (5-2) and the right support rod of the rear copper rod track (5-20) are respectively fixed on the front and rear of the right crossbeam of the experimental instrument base (2) The front copper rod guide rail (7-1) and the rear copper rod guide rail (7-2) are respectively installed on the corresponding left and right support rods of the front copper rod track and the left and right support rods of the rear copper rod track. On the corresponding sleeve column at the upper end, the front and rear copper rod guide rails are close to the upper surface of the large rectangular coil (8) and on the same plane; the front copper rod guide rail (7-1) and the rear copper rod guide rail (7-2) are vertical Place the energized copper rod (10), the middle section of the energized copper rod (10) is a conductive rectangular light-blocking copper sheet (10-0), the cross-sectional area of the conductive rectangular light-blocking copper sheet (10-0) and the energized copper rod (10) The cross-sectional areas at both ends are equal; the front copper rod guide rail (7-1) and the rear copper rod guide rail (7-2) are connected to the wires through the front copper rod guide rail (7-10) and the rear copper rod guide rail (7-20) respectively. ) to the corresponding terminal of the electric control box (1). 2. The experimental instrument for demonstration and quantitative measurement of the force of a copper rod in a magnetic field according to claim 1, characterized in that: the supporting feet of the left support rod (6-1) of the through-beam photoelectric sensing receiver are lifted from the base of the experimental instrument. (2) The front and rear copper rod guide rail support feet of the left crossbeam move the slide (2-00) to the center of the left crossbeam, and the right support rod (6-2) of the through-beam photoelectric sensor receiver moves from the base of the experimental instrument (2) The front and rear copper rod guide rail support feet of the right cross beam (2) are inserted into the sliding slide (2-00) to the center of the right cross beam, and the two support rods are fixed with fixing screws respectively. 3. The experimental instrument for demonstration and quantitative measurement of copper rod stress in a magnetic field according to claim 1, characterized in that: the left support rod (5-1) of the front copper rod track and the left support rod (5-1) of the rear copper rod track. The support legs of 10) are respectively inserted into the left beam from the front and rear copper rod guide rail support foot moving slides (2-00) of the left beam of the experimental instrument base (2) and at corresponding positions symmetrical with respect to the center of the left beam. The two support rods Fix with fixing screws. The center distance between the left support rod of the front copper rod track (5-1) and the left support rod of the rear copper rod track (5-10) is the effective length L value of the energized copper rod (10); the front copper rod track The support legs of the right support rod (5-2) and the right support rod of the rear copper rod track (5-20) are respectively moved from the front and rear copper rod guide rail support foot moving slides (2-00) of the right crossbeam of the experimental instrument base (2) It is inserted into the right cross beam and is symmetrical about the center of the right cross beam. The two support rods are fixed with fixing screws. The right support rod of the front copper rod track (5-2) and the right support rod of the rear copper rod track (5-20) are The center distance is the effective length L of the energized copper rod (10). 4. The experimental instrument for demonstration and quantitative measurement of copper rod stress in a magnetic field according to claim 1, characterized in that: the front copper rod guide rail (7-1) and the rear copper rod guide rail (7-2) are respectively installed on corresponding The left and right support rods of the front copper rod track and the upper ends of the left and right support rods of the rear copper rod track are fixed on the corresponding sets of columns with fixing screws. 5. The experimental instrument for demonstrating and quantitatively measuring the force of a copper rod in a magnetic field according to claim 1, characterized in that: the left and right fixed ferrules of the upper photoelectric sensing receiver fixed longitudinal beam (4) are respectively placed on the opposite side. The left support rod (6-1) of the through-beam photoelectric sensor receiver and the right support rod (6-2) of the through-beam photoelectric sensor receiver are mounted on the sleeve posts at the top and fixed with fixing screws. 6. The experimental instrument for demonstration and quantitative measurement of copper rod stress in a magnetic field according to claim 1, characterized in that: the scale of the upper photoelectric sensing receiver fixed longitudinal beam (4) is fixed to the lower photoelectric sensing transmitter. The scale of the longitudinal beam (3) corresponds to the upper and lower parts. The scale positions of the first through-beam photoelectric sensor receiver (4-1) and the second through-beam photoelectric sensor receiver (4-2) are respectively in line with the first and second through-beam photoelectric sensor receivers. The scale positions of the one through-beam photoelectric sensor transmitter (3-1) and the second through-beam photoelectric sensor transmitter (3-2) correspond to each other. 7. The experimental instrument for demonstration and quantitative measurement of copper rod stress in a magnetic field according to claim 1, characterized in that: the electric control box (1) includes an electric control box power switch (1-0) and an electric control box indicator light. (1-1), through-beam photoelectric sensing time display switch (1-2), through-beam photoelectric sensing time display (1-3), constant current source provides the current direction and size increase and decrease knob for the coil ( 1-4), the constant current source current size display (1-5) and the constant current source provide the current direction and size increase and decrease knob (1-6) for the energized copper rod.