JPH0230507B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a Foucault pendulum experimental device.

A Foucault pendulum is a pendulum used to investigate the effect of Earth's rotation on the plane of simple harmonic vibration.

The vibration plane of a pendulum installed on the earth's surface rotates in the direction of the clock hands in the northern hemisphere when viewed from above due to the influence of the earth's rotation, and the hourly rotation angle θ at a latitude point is given by the formula θ=15°sin It is calculated by J. Foucanlt in 1851 string length 67
An experiment was carried out by hanging a 28 kg pendulum from the center of the earth, and it was used as evidence of the earth's rotation.

Conventionally, when conducting such experiments, it has been difficult to maintain the amplitude constant, especially in long-term experiments, and it has been impossible to match theoretical values with experimental values.

A necessary condition for a Foucault pendulum is that it is a simple harmonic motion. In other words, no parasitic vibrations should occur.

The simple vibration plane must be able to rotate 360° around a vertical line drawn from a fixed fulcrum.

To maintain a constant amplitude for a long time.

can be mentioned.

An object of the present invention is to provide a small-sized Foucault pendulum experimental device that satisfies the above conditions and allows long-term experimental values to match theoretical values.

In this invention, an electromagnet is installed so that magnetic force is exerted from a single point, and an attractive force of the same magnetic force is exerted on a pendulum on a concentric circle centered on a vertical line taken down from a fixed fulcrum that fixes the upper end of the swinging string, and the pendulum vibrates. The present invention is characterized in that an electromagnetic force control device is provided which inputs a signal to an electromagnetic coil only in a certain section of the pendulum's journey toward the vertical line, and applies an attractive force to the pendulum.

An embodiment of the present invention will be described below based on the drawings.

In Fig. 1, the fixed fulcrum 1 that supports the pendulum is
The length of the swinging thread 2 can be adjusted by screwing (not shown).

The center of the inner diameter of the shearon ring 3 is arranged below the fixed fulcrum 1 so that it coincides with a vertical line drawn down from the fixed fulcrum 1. The Sharon ring is for preventing parasitic vibrations of the pendulum, and is ring-shaped with a circular perforation. The radius of the circular perforation is slightly smaller than the amplitude of the swinging thread. In the present invention, in order to pursue experimental values that are more consistent with theoretical values, the inner circumferential cross section of the Searon ring is made into a substantially triangular shape, so that the side effects on the pendulum that occur due to the swinging thread coming into contact with the Searon ring are reduced. In order to prevent the effect as much as possible,
, and is trying to make point contact with the Syaron ring 3.

The pendulum 4 has a spherical shape, and a swinging thread 2 is attached to the upper end of the pendulum 4.
A conical protrusion 5 and a conical protrusion 5 are connected to the lower end of the pendulum 4.
An inner circumferential reflective surface 6 is provided on the outer periphery of the base end, with the center point thereof being centered on the axis of the pendulum 4.

The pendulum 4 may have any shape as long as it functions as a circular or truncated conical pendulum.

The protrusion 5 is made of a magnetic metal such as iron. Even if the entire pendulum sphere is made of magnetic metal, there will be no problem in accuracy during experiments lasting several hours.

However, in order to obtain long-term, high-precision experimental values as directed by the present invention, the main body of the pendulum 4 is made of a non-magnetic metal such as brass, and the tip of the protrusion 5 made of a magnetic metal is shaped like a cone. The aim is to prevent the occurrence of side effects as much as possible.

Furthermore, in this embodiment, the tip of the protrusion 5 of the pendulum 4 is made into a conical shape with the intention of receiving the attractive force of the electromagnet with the conical tip and obtaining more accurate experimental measurements.

The angle display scale plate 7 displays angles centered on the above-mentioned vertical line.

The excitation control device provided below the pendulum 4 consists of an electromagnet 8 and an electromagnetic force control device.

The upwardly directed tip 8' of the electromagnetic core is conical and is located on the vertical line and close to the stationary pendulum 4.

The shape of the tip 8' of the core of the electromagnet may be other shapes as long as they exert the same electromagnetic force on concentric circles around the tip. .

The electromagnetic force control device includes a light emitter 10, a photoreceptor 11, and an electric circuit 12 that controls energization of the electromagnetic coil 9.

The light emitting body 10 and the light receiving body 11 are provided near the electromagnet 8 so as to receive the light beam reflected by the reflecting surface 6 just before the vibrating pendulum 4 passes through the core tip 8' of the electromagnet.

The electric circuit 12 connects the light emitting element 1 as shown in FIG.
0, a light receiving element 11, an excitation section 13, Schmitt circuits 14, 14', a delay circuit 15, and a switching transistor 16.

Although an infrared LED 10 is used as the light emitting element in this embodiment, it may be a visible light LED or the like.

This infrared LED 10 is connected to the positive
Connect to a negative power source and emit infrared light upwards.

The excitation section 13 has an electromagnetic coil 9 connected in series with a variable resistor 17, one end of which is connected to a positive power supply, and the other end of which is connected to the collector side of a switching transistor 16 whose emitter is grounded.

The switching transistor 16 is a switching element, and the input potential on the base side is "H" or
It has the function of opening and closing energization to the electromagnetic coil 9 depending on whether it is "L" or not.

The Schmitt circuits 14, 14' provided between the positive power supply side of the excitation section 13 and the base side of the switching transistor 16 are composed of logic elements,
It shapes the input signal into a square wave and also has a polarity conversion function.

A light receiving element such as a photodiode 11 has one end connected to the input side of the Schmitt circuit 14 and the other end grounded to a negative power supply.

The photodiode 11 has a function of rapidly reducing its resistance when it receives light.

Sensitivity adjustment of such a phototransistor is performed using a variable resistor 20.

Delay circuit 15 includes capacitor 1 connected in parallel.
8 and a variable resistor 19, one of which is connected to the Schmitt circuits 14 and 14', and the other is grounded to the negative power supply.

Next, the relationship between the pendulum 4 and the excitation control device will be explained with reference to FIGS. 2 and 3.

When the phototransistor 11 receives the light beam reflected by the reflecting surface 6 of the pendulum 4 just before the vibrating pendulum 4 passes the tip 8' of the core of the electromagnet (FIG. 3, 2 and 5), the resistance of the phototransistor 11 increases. As the value decreases, the potential at point a in Figure 3 decreases, so the input potential on the base side of switching transistor 16 (point c in Figure 3) becomes "L" and the current to electromagnetic coil 9 is immediately cut off. , the potential at point b becomes "H" and the capacitor 18 is charged.

Therefore, when the pendulum 4 passes the tip of the electromagnet, the pendulum attraction effect due to electromagnetic force becomes zero (OFF).
(Figure 3 2, 5).

When the pendulum 4 passes the tip of the electromagnet and the phototransistor 11 no longer receives the reflected light, the resistance value of the phototransistor 11 increases and the potential at point a in FIG. 3 becomes "H", but there is a delay. Due to the discharge of the capacitor 18 of the circuit 15, the base side of the switching transistor 16 (point c) for a certain period of time
The input potential of is maintained in the "L" state, the energization of the electromagnetic coil 9 is maintained in a cut-off state, and the electromagnetic force remains in a zero state for a certain period of time (OFF) (FIGS. 3 and 6).

Thereafter, when the input potential on the base side (point c) of the switching transistor 16 returns to "H", the electromagnetic coil 9
energization is started, and the pendulum 4 is attracted by electromagnetic force (ON) (Fig. 3, 1, 4).

The timing of opening and closing of this switching transistor 16 is adjusted by a variable resistor 19 in parallel with a capacitor 18 so that the electromagnet is activated only on the way that the pendulum 4 moves toward the core tip 8' of the electromagnet.

Further, the strength of the electromagnetic force is adjusted by a variable resistor 17 in series with the electromagnetic coil 9 in the excitation section 13.

Note that once the variable resistors 17, 19, and 20 are adjusted, there is no need to adjust them again.

Figure 4 shows the actual measured values obtained during a 43-hour experiment using the Foucault pendulum experimental device described above. The solid line shows the theoretical value in the above equation, and the measured value is plotted with points.

As is clear from the above description, the present invention with the above configuration allows Foucault pendulum experiments to be carried out over a long period of time, which was considered impossible in the past, even though it is a miniaturized experimental device. It becomes possible to provide consistent experimental values.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of an embodiment of the present invention, Fig. 2 is an electric circuit in an electromagnetic force control device, Fig. 3 is a diagram showing the relationship between the movement of a pendulum and the action of electromagnetic force, and Fig. 4 is a diagram of the invention 2 is a table showing measured values obtained through an experiment using an example. 4... Pendulum, 5... Magnetic metal, 6... Reflective surface, 8...
Electromagnet, 10... Light emitter, 11... Photoreceptor, 12... Electromagnetic force control electric circuit, 18... Capacitor.

Claims (1)

[Scope of Claims] 1. A Foucault pendulum experimental device consisting of a fixed fulcrum that fixes one end of the pendulum, a pendulum connected at the other end of the pendulum, and an angle display scale plate whose center point is on a vertical line taken down from the fixed fulcrum. In this step, a Syaron ring having an inner diameter center on the vertical line is installed under the fixed fulcrum through the swinging thread, and the pendulum has a protrusion made of magnetic metal at its lower end and a reflective surface formed on the outer periphery of the proximal end of the pendulum. an electromagnet having a core tip facing upward on a vertical line close to the protrusion tip of the lower end of the pendulum in a stationary state, a light emitting body and a light receiving body being disposed near the electromagnet, and the vibrating pendulum being connected to the electromagnet. Immediately before passing through the tip of the core, the light beam from the light emitting body is reflected by the reflecting surface and is received by the light receiving body, and upon receiving this light, the electricity to the electromagnetic coil is stopped, and the stopped state is maintained for a certain period of time. A Foucault pendulum experimental device characterized by being provided with an electric circuit that functions to start energizing the electromagnetic coil again after maintaining the current. 2. In claim 1, the tip of the protrusion made of magnetic metal is shaped like a cone, and the shape of the reflective surface formed on the outer periphery of the proximal end of the protrusion is on the circumference, facing upward in the vertical line. The tip of the electromagnet core is arranged in a conical shape. 3. In claim 1, the inner diameter of the Syaron ring has a substantially triangular cross section.