CN107991208B

CN107991208B - Method for reducing equilibrium voltage of Millikan oil drops measured by air pressure

Info

Publication number: CN107991208B
Application number: CN201711164529.7A
Authority: CN
Inventors: 雍志华; 胡再国
Original assignee: Sichuan University
Current assignee: Sichuan University
Priority date: 2015-12-08
Filing date: 2015-12-08
Publication date: 2020-06-19
Anticipated expiration: 2035-12-08
Also published as: CN105510188A; CN108007828A; CN105510188B; CN107991208A

Abstract

The method for reducing the gas pressure to measure the Millikan oil drop balance voltage has the technical scheme that the influence on measuring the oil drop balance voltage is brought by the unbalanced acting force of oil drops caused by reducing gas collision: the method for reducing the equilibrium voltage of the Millikan oil drop measured by air pressure is characterized by comprising the following steps of: the air pressure in the oil drop chamber is reduced to enable the brownian motion phenomenon of the oil drops to be negligible, wherein the negligible phenomenon means that the oil drops cannot be seen in a horizontal direction to drift, namely the oil drops only move in a vertical direction. The beneficial effects are that: the air pressure in the oil drop chamber is reduced, so that the Brownian motion phenomenon of the oil drops can be ignored, and the balance voltage of the oil drops can be more accurately measured; the through holes uniformly distributed on the side surface of the cylinder can promote air flow in the horizontal direction to be balanced with oil drops, so that oil drop movement caused by vacuumizing is avoided.

Description

Method for reducing equilibrium voltage of Millikan oil drops measured by air pressure

The application is a divisional application of patent application of 12.8.2015 of the applicant, and the original patent name is 'method for measuring Millikan oil drop equilibrium voltage by reducing air pressure', and the original patent number is '201510895837.1'.

Technical Field

The invention relates to the field of measurement of physical quantities.

Background

When an object is judged to be in force balance, the object is generally in a static state or in uniform linear motion as a judgment standard, and whether the object is in force balance (the resultant force is 0) is judged in most cases by whether the object is in a static state or not.

The diameter of the Millikan oil drop is approximately in the magnitude order of micrometers, the distance between air molecules is approximately in the magnitude order of nanometers, when the oil drop is close to balance, the oil drop is equivalent to suspended particles, and due to irregular collision of the air molecules, Brownian motion, namely irregular disordered motion, of the oil drop particles can occur, so that judgment of stress balance of the oil drop is difficult. For larger oil drops, the unbalanced acting force of air molecules on the oil drops is smaller than the gravity of the oil drops (namely, the oil drops have large mass and large inertia), the stability of the oil drops during suspension is better, but the oil drops have large mass and small action of the air molecules, the falling speed is faster (namely, the falling time is shorter), and the error of measuring the falling time is larger (limited by the physiological reaction speed of 0.1 second of a person, because the oil drops are smaller, the time cannot be measured by devices such as a photoelectric gate and the like, and generally, the time is measured by judging the position of the oil drops by the person after the enlargement of a microscope and starting and stopping the operation by the person; when oil drops are small, the imbalance under the collision action of air molecules is large in expression, brownian motion is obvious, whether the oil drops are in a balanced state or not cannot be accurately determined, and therefore the measurement error of balanced voltage is large.

Disclosure of Invention

In order to reduce the influence of unbalanced acting force of oil drops caused by gas collision on the measurement of oil drop balance voltage, the invention designs a method for reducing the air pressure to measure the Millikan oil drop balance voltage.

The invention adopts the technical scheme that the purpose of the invention is realized by: the method for reducing the equilibrium voltage of the Millikan oil drop measured by air pressure is characterized by comprising the following steps of: the air pressure in the oil drop chamber is reduced to enable the brownian motion phenomenon of the oil drops to be negligible, wherein the negligible phenomenon means that the oil drops can not drift in the horizontal direction, namely the oil drops (under the action of electric field force and gravity) only move in the vertical direction; the oil dropping hole of the oil dropping chamber is sealed, the lower pole plate of the oil dropping chamber and the lower end of the annular supporting frame of the oil dropping chamber are in a sealing state, the upper pole plate of the oil dropping chamber and the upper end of the annular supporting frame of the oil dropping chamber are in a sealing state, the annular supporting frame, the observation hole and the light inlet hole are in a sealing state, and a through hole is arranged on the side surface of the annular supporting frame and communicated with an air inlet pipeline of the vacuum device.

A transparent hard cylinder is arranged on the inner side of the circular ring-shaped support frame, and the height of the cylinder is equal to the height of the circular ring-shaped support frame; the cylinder and the circular ring-shaped support frame have the same central axis, the outer diameter of the cylinder is 0.5-1mm smaller than the inner diameter of the circular ring-shaped support frame, namely the radial distance between the outer side of the cylinder and the inner side of the circular ring-shaped support frame is 0.5-1mm, the cylinder and the circular ring-shaped support frame have the same circle center in the horizontal cross section, the difference between the outer radius of the cylinder in the diameter direction and the inner radius of the circular ring-shaped support frame is the radial distance, through holes are uniformly distributed on the side surface of the cylinder, and the diameter of the through holes is 5-20% of the diameter of the through holes on the side surface.

The invention has the beneficial effects that: the air pressure in the oil drop chamber is reduced, so that the Brownian motion phenomenon of the oil drops can be ignored, and the balance voltage of the oil drops can be more accurately measured; the through holes uniformly distributed on the side surface of the cylinder can promote air flow in the horizontal direction to be balanced with oil drops, so that oil drop movement caused by vacuumizing is avoided. The invention only needs to observe that oil drops do not shift in the horizontal direction, the influence of air pressure collision on balance voltage measurement can be ignored, the balance voltage knob is adjusted to keep oil drops balanced in the vertical direction, the measurement is completed, and then the oil drops can be gradually evacuated to recover to normal pressure (the prior art can solve the problem from vacuum to normal pressure).

Drawings

FIG. 1 is a schematic diagram of experimental apparatus components of Chengdu century Zhongke apparatus Co., Ltd, and FIG. 2 is a schematic diagram of a drop box apparatus; FIG. 3 is a device for equalizing air flow in a drip chamber;

the device comprises a CCD box 1, a CCD box 2, a power socket 3, a focusing knob 4, a Q9 video interface 5, an optical system 6, a lens 7, an observation hole 8, an upper pole plate pressure spring 9, a light inlet hole 10, a light source 11, a confirmation key 12, a state indicator lamp 13, a balance and lifting switch key 14, a 0V and work switch key 15, a timing start and end switch key 16, a level bubble 17, a voltage adjusting knob 18, a set screw 19, a power switch 20, a drop tube storage box placing ring 21 and leveling screws (3); 31. the oil-spraying device comprises a spraying opening, a 32 oil inlet amount switch, a 33 wind shield, a 34 upper pole plate, a 35 oil drop chamber, a 36 lower pole plate, a 37 oil mist cup, a 38 oil dropping hole, a 39 cylinder, a 40 through hole.

Detailed Description

The prior art is as follows:

the prior art oil drop box is generally cylindrical, a lower pole plate 36 is arranged at the lower part of the oil drop box, the lower pole plate provides an electrode for the oil drop box, the oil drop box is generally arranged as a negative pole, a hollow part enclosed by the cylinder is an oil drop suspension space which is called an oil drop chamber 35, the height of the inner space of the oil drop chamber 35 is generally 5mm, three sealed transparent holes (sealed by transparent materials and transparent to light and sealed to gas) are arranged on the side surface of the cylinder, one of the sealed transparent holes is an observation hole 7, the other two transparent holes are light inlet holes 9, the light of the light inlet holes 9 comes from a light emitting diode light source 10, the upper part of the cylinder covers an upper pole plate 34, the upper surface of the upper pole plate 34 is in contact with an upper pole plate pressure spring 8, and the upper pressure. The center of the upper pole plate 34 is provided with an oil dropping hole 38, and the oil dropping hole 38 is a small hole with the diameter of about 0.5 mm. The voltage adjusting knob 17 adjusts the voltage V applied between the upper and

lower plates

34 and 36, thereby adjusting the electric field E = V/5mm between the upper and

lower plates

34 and 36.

The outer side of the oil drop box is provided with a ring-shaped wind shield 33 to avoid the influence of the outside air flow on oil drops, the upper part of the wind shield 33 is provided with an oil mist cup 37, the oil mist cup 37 generally comprises a round cylinder, an upper cover and a bottom cover, the side surface of the round cylinder is provided with a spray port 31, the oil mist cup 37 is provided with the upper cover and the bottom cover, the upper cover, the bottom cover and the round cylinder form a cup-shaped structure, the bottom cover is provided with a hole, the hole of the bottom cover is covered by a metal sheet, the metal sheet can move in the diameter direction of the bottom cover, the metal sheet is also provided with a hole, the hole diameter of the metal sheet is generally equal to the hole diameter of the hole of the bottom cover, when the metal sheet is moved to enable the hole of the metal sheet to be opposite to the hole of the bottom cover, part of oil drops sprayed on the oil mist cup pass through the two opposite holes.

The light from the light source 10 illuminates the inner space of the oil drop chamber 35, the lens 6, the optical system 5 and the focusing knob 3 make the suspended oil drops image to the CCD box 1, and the image of the CCD box 1 is connected to the display through the Q9 video interface 4.

The state indicator light 12 indicates whether the oil drop balance is adjusted or the oil drop is in a lifting state, wherein the lifting is to pull the oil drop to the upper part of a visual field, and a voltage of about 200V is added on the basis of the balance voltage to promote the oil drop to move upwards; a balance and elevation switching key 13, a balance and elevation switching button, whose state is determined by the state indicating lamp 12. And 0V and a work switching key 14, wherein 0V is that after the electric field force is cancelled, oil drops move downwards in a gravity field and fall at a constant speed (if Brownian motion is not considered) after accelerated movement for a certain distance under the resistance of air, and work means that under the action of the electric field, balance voltage is adjusted or lifting voltage for lifting the oil drops upwards is adjusted.

The timer start/end switch 15 starts the timer and stops the timer when the timer ends. Since the electric field is perpendicular to the upper plate 34 and the lower plate 36 which are in parallel, and the gravity is in the vertical direction, it is necessary to adjust the upper plate 34 and the lower plate 36 to be horizontal, so that the direction of the gravity is parallel to the direction of the electric field, and therefore the leveling bubble 16 is indicated to be horizontal by adjusting 3 leveling screws 21 (three points determine a plane). The set screw 18 is a fixing device of the CCD box base, the power switch 19 is a power switch for the instrument to work, and the oil dropping pipe storage box installation ring 20 is a storage device for facilitating the oil dropping pipe when not in use, so that the liquid oil of the oil dropping pipe is prevented from dropping on a desktop. The power socket 2 is connected to a 220V alternating current power supply and is an input power supply of the instrument; the confirmation key 11 can record data on a display screen (essentially in a memory), delete current data, calculate the charge amount of oil drops after measurement, and the like.

The improvement measures are as follows:

the method for reducing the balance voltage of the Millikan oil drop measured by air pressure has the advantages that the diameter of the Millikan oil drop is approximately in the order of micrometers, the space between air molecules is approximately in the order of nanometers, and the difference between the air molecules and the air molecules is 10 DEG³On the order of magnitude, the drop area is the square of the length, so the number of molecules in contact with the drop surface is 10⁶The magnitude of the order of magnitude, brownian motion caused by fluctuation is obvious, if the number of contact with air molecules is reduced, namely the air pressure of air is reduced, the number of contact between oil drops and the air molecules can be reduced, fluctuation of kinetic energy of the air molecules (unbalanced force generated by collision acting on the oil drops) is also greatly reduced, and therefore, the technical scheme is as follows: the reduced air pressure inside the drop chamber 35 makes the brownian motion phenomenon of the drops negligible, which means that the drops do not drift in the horizontal direction, i.e. the drops only move in the vertical direction (due to the action of the vertical electric field and gravity).

Since the present invention is concerned with the equilibrium state of the oil droplets, specific data on air pressure may not be measured; if a measurement is to be made, a probe of the gas pressure can be arranged inside the gas duct of the gas withdrawal device.

To reduce the pressure of air, the passage of the oil dropping hole 38 can be utilized, the oil dropping hole 38 of the oil drop chamber 35 is communicated with an air inlet pipeline of a vacuum device (the vacuum device is a prior art and reduces air pressure by sucking away air), the lower pole plate 36 of the oil drop chamber 35 and the lower end of the annular support frame of the oil drop chamber 35 are in a sealed state, and the upper pole plate 34 of the oil drop chamber 35 and the upper end of the annular support frame of the oil drop chamber 35 are in a sealed state; the outer side of the oil drop chamber 35 is provided with an observation hole 7 and a light inlet hole 9 of a ring-shaped supporting frame sealed by an annular transparent film. If the observation hole 7 and the light inlet hole 9 are leaked, the annular transparent material is forced to be directed to the oil drop chamber 35 under the action of the internal and external pressure difference, so that the transparent film is deformed inwards, gaps of the transparent film are filled, and the sealing effect is achieved. The rotational speed of adjustment vacuum apparatus's motor, it is little to the influence that the suspension drips that the messenger evacuation leads to the flow of air in the oil drip chamber 35, and the influence is little to indicate not more obvious process of moving up, and the evacuation leads to dripping to receive an ascending effort, can be through the balanced voltage hedging this effect of adjusting oil drip, and when the vacuum was close evacuating device's limit, the evacuation leads to dripping to receive an ascending effort and disappears, and at this moment, brownian motion is also not obvious (relative and ordinary pressure), is favorable to accurate regulation balanced voltage.

Oil drip box comprises ring shape support frame and the last polar plate 34 of ring shape support frame upper end and the bottom polar plate 36 of bottom, the space at oil drip box place is sealed to a sealed mode contact of sealed cover, the electric wire of the bottom polar plate 36 of oil drip box and the electric wire of last polar plate 34 and sealed cover pass through (this can be realized by prior art, for example, wrap up a sealed pad through the melting mode in the outside of electric wire, sealed pad is located the breach of sealed cover bottom, the area of sealed pad is greater than the area of breach, the size of breach mainly holds the radial size of electric wire, the evacuation produces the indoor side strength of a directional oil drip, make this breach sealed), the sealed cover has a through-hole to communicate vacuum apparatus's admission line.

The oil dropping hole of the oil dropping chamber 35 is sealed, the lower pole plate 36 of the oil dropping chamber 35 and the lower end of the annular supporting frame of the oil dropping chamber 35 are in a sealing state, the upper pole plate 34 of the oil dropping chamber 35 and the upper end of the annular supporting frame of the oil dropping chamber 35 are in a sealing state, the annular supporting frame, the observation hole 7 and the light inlet hole 9 are in a sealing state (made of soft transparent materials), and the side surface of the annular supporting frame is provided with an air inlet pipeline communicated with a vacuum device through a through hole.

Claims

1. Reduce method that atmospheric pressure measures michigan oil drip balanced voltage, the oilhole (38) that falls of oil drip room (35) are sealed, and bottom plate (36) of oil drip room (35) are in encapsulated situation with the lower extreme of the ring shape support frame of oil drip room (35), and oil drip room (35) are gone up polar plate (34) and the upper end of the ring shape support frame of oil drip room (35) and are in encapsulated situation, and ring shape support frame all is in encapsulated situation with observation hole (7) and light inlet hole (9), characterized by: a through hole is arranged on the side surface of the circular ring-shaped support frame and is communicated with an air inlet pipeline of a vacuum device; a transparent hard cylinder (39) is arranged on the inner side of the circular ring-shaped support frame, and the height of the cylinder (39) is equal to the height of the circular ring-shaped support frame; the cylinder (39) and the circular ring-shaped support frame have the same central axis, the outer diameter of the cylinder (39) is 0.5-1mm smaller than the inner diameter of the circular ring-shaped support frame, namely the radial distance between the outer side of the cylinder (39) and the inner side of the circular ring-shaped support frame is 0.5-1mm, as the cylinder (39) and the circular ring-shaped support frame have the same central axis, the cylinder (39) and the circular ring-shaped support frame have the same center in the cross section in the horizontal direction, the difference between the outer radius of the cylinder (39) and the inner radius of the circular ring-shaped support frame in one diameter direction is the radial distance, through holes (40) are uniformly distributed on the side surface of the cylinder (39), and the diameter of the through holes; the air pressure in the oil drop chamber (35) is reduced to enable the brownian motion phenomenon of the oil drops to be negligible, wherein the negligible phenomenon means that the oil drops can not be seen in the horizontal direction to drift, namely, the oil drops only move in the vertical direction.