Like terrestrial magnetotellurics, ocean magnetotellurics (Ocean MT) also use natural electromagnetic fields (passive sources). Marine MT typically places magnetic signal receivers (magnetic probes) and electrical signal receivers (electrodes) on the seabed. Magnetic receivers are not much different from terrestrial ones. As for the arrangement of electrodes, due to the difficulty of laying large electrode spacings on the seabed, a device called a saltwater bridge chopper is gradually used. Its electrode spacing is only a few meters and can be connected to the instrument box.
Figure 4?4?1 Attenuation of horizontal electromagnetic fields in seawater
As seawater has good electrical conductivity, when electromagnetic waves are transmitted from the sea surface to the seafloor, most of their energy being absorbeded by sea water, its intensity is strongly attenuated, in particular the high frequency part attenuates more quickly. In Figure 4?4?1, the relationship curve between the ratio and period of the seabed electromagnetic field (Esf and Bsf) and the seawater surface electromagnetic field (Ess and Bss) is plotted when the depth of the seabed is 5000 m, 500 m and 100 m. Among them, the conductivity of seawater σ = 3.2 S/m is taken, and the conductivity σ of seabed rock is 0.005 S/m (dashed line) and 0.05 S/m, respectively. (continuous line).
Similarly, it can be seen on the spectrum of the electric field signal measured on the seabed (Figure 4?4?2) that the high frequency part of the electromagnetic wave was strongly attenuated due to of the absorption of sea water.
Figure 4?4?2 Electric field signal spectrum measured on the sea floor
Due to the movement of water from conductive sea in the magnetic fieldterrestrial ethics, electromagnetic fields can be generated. is relative to the source of the MT field. Electromagnetic waves hitting the Earth's surface vertically are a kind of interference, which can also be called "pollution" for the source of the MV field. The frequency band and degree of this "pollution" impact is related to the spatial wavelength and time period of seawater movement as well as the strength of the geomagnetic field in the location. geographical.
Consequently, the frequency bands that can be used by marine MTs are very limited compared to those on land. Current marine MT work is mainly used to study the lithosphere and asthenosphere at depths of several hundred kilometers. This is the only method to date to study the electrical structure of the seabed below 30 km. The research results show that there is aelectrical mutation surface at a depth of 50 to 100 km below the seafloor. Above is a low conductivity layer and below is a high conductivity layer. The change in conductivity is 0.05 to 0.2 S/m. Due to its high lateral resolution, MT is also a useful tool for studying mid-ocean ridges where electrical levels are uneven due to hydrothermal changes.
What are the differences in microwave absorption capabilities between sucrose, salt and butter?
The advantages dancing salt for parents in their children's education are as follows:
This small science experiment can develop children's practical abilities while increasing their interest in science. In small experiments, children can not only have fun, but also understand some simple scientific phenomena and knowledgeples and improve their creativity. It allows children to first discover science in different aspects through practical activities and vocalizations. The charm and experience of the pleasure of science.
1. Dancing salt is the principle of resonance
This means that a physical system vibrates at a specific frequency with a greater amplitude than other frequencies. . It is used in many areas of life. For example, when construction workers pour concrete walls or floors, in order to improve the quality, they always use an oscillator to vibrate when pouring concrete, so that the concrete becomes closer and stronger due to oscillation.
Another example is the microwave oven commonly used in our homes. When heating food, a strong oscillating electromagnetic field is generated in the oven, which causes the molecules to vibrate and resonate.s of water contained in food, thus converting electromagnetic radiation. energy into thermal energy, causing the temperature of the food to rise rapidly.
2. Experimental Conclusions
Through the experiment, we will find that the salt powder which is at rest at the beginning will become static after making a sound for the salt powder. Shake it on the plastic wrap, and the louder the volume, the more violently the salt is shaken. Sound is a sound wave generated by the vibration of an object, propagates through a medium and constitutes a wave phenomenon that can be detected by the hearing organs of humans or animals.
When the sound is made against the salt powder on the glass, it causes the air in the glass to vibrate, which in turn causes the plastic film to vibrate with it, so we see the salt on glass. the plastic film also vibrates. In addition, the louder the sound, the greater the amplitude of vibration.one of the object is large. Therefore, changing the volume of the sound will also cause the amplitude of the salt grains to shake accordingly.
3. Precautions for performing the dancing salt experiment
1 This experiment requires an adult to accompany you throughout the process. to ensure safety.
2. Please handle the glass bowl with care.
3. When spreading salt, be gentle with your hands to avoid spilling salt on the table.
4. Do not rub your eyes with your hands that touch the grains of salt. Wash your little hands after the activity.
5. Once the activity is complete, organize and summarize the material.
How was electricity discovered? Who discovered it?
The differences in the microwave absorption capabilities of sucrose, salt and butter are mainly reflected in the following two aspects:
1 . List of ingredients : The roles and amounts of sucrose, salt and butter in the ingredient list will affect their microwave absorption during the cooking process.
* Sucrose: This is a commonly used sweetener that can improve the taste of foods. Among the food materials suitable for microwave ovens, the addition of sucrose can enhance the heating effect of microwaves on starchy materials, significantly increasing the rate of temperature increase of the materials, and as the Sucrose content increases, this enhanced effect becomes more evident.
* Table salt: Mainly used as a flavoring agent and preservative, which can increase the salinity of foods and inhibit the growth of microorganisms. However, salt should be used as little as possible when cooking in the microwave, especially for meat, as salt will make the meat coarser.
* Cream: higher water contente,In 30 ml of foaming cream, water represents 59.6%. Since water absorbs microwaves, when cream is heated in the microwave, the water particles vibrate and become hotter.
2. Production Steps: In the specific cooking process, how these ingredients are used will also affect their microwave absorption.
* Sucrose: After adding sucrose to microwave-safe ingredients, you must first stir or mix the ingredients so that the sucrose can melt completely. Next, heat the ingredients in the microwave.
* Table salt: When cooking in a microwave oven, if you must use table salt, it is best to add it after the cooking time is over to avoid affect the heating effect.
* Cream: When heating cream in the microwave, it is best to pour it into a container rather than directly into it.in the microwave. If the ingredients contain cream or water, they should also be mixed evenly to ensure even heating.
In general, sucrose and cream are heated primarily by water absorption when heated in a microwave oven, while salt should be used as little as possible or even avoided.
The Arabs were probably the first to understand the nature of lightning. They may also have recognized other sources of electricity before other groups. As early as the 15th century, the Arabs created the Arabic word "raad" for "lightning" and used this word to refer to electric rays.
In ancient cultures of the Mediterranean region, there have long been written records that rubbing amber sticks with cat hair would attract feathers and other substances. Around 600 BC, the Greek philosopher Thales (640-546 BC) made a seriesobservations on static electricity. From these observations, he believed that friction made amber magnetized.
This is very different from the properties of minerals like magnetite; magnetite is naturally magnetic. Thales' opinion was incorrect. But later, science will confirm the close relationship between magnetism and electricity.
Detailed information
Electrification phenomenon:
1. Electrification by friction consists of charging objects by physical phenomena of friction. The triboelectricity step involves using two different insulators to rub against each other, so that their outermost electrons receive enough energy to transfer. After electrification by friction, both insulators must carry the same amount of opposing electricity.
2. Electrostatic adsorption means that when an electrostatically charged object becomesApproaching a small, non-statically charged object, the free charge on the surface of the small object is transferred, inducing the electrical property opposite to that of the electrostatic object. charged object, and is absorbed. Attracts and attaches to electrostatically charged objects. Using the principle of electrostatic attraction of light and small objects, the adsorption effect of industrial dust can be achieved.
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