Under a temperature difference between two points of all materials, an electromotive force (voltage) is generated as electric charges are migrated.
This electromotive force causes an electric current to flow and generate a magnetic field (Framing’s left-hand rule).
In this research, a temperature difference was generated between two points of a material such as soil and the potential difference was measured.
Figure 1 shows the temperature difference and charge transfer state of materials.
The materials that are charged positively on the high-temperature side are defined as “positive temperature polarity materials” and those that are charged negatively on the high-temperature side are defined as “negative temperature polarity materials.”
For example, water and iron, are positively charged on the high-temperature side and negatively charged on the low-temperature side. (Table 1).
Contrarily, the negative temperature polarity materials, such as soil and ice, are negatively charged on the high-temperature side and positively charged on the low-temperature side (Table 1).
Water, a positive temperature polarity material, is positively charged on the high-temperature side and negatively charged on the low-temperature side. However, when water is frozen and turns into ice below 0°C, it becomes a negative temperature polarity material with the reversal of the charge polarity.
Because water and ice have opposite temperature polarities, when the cloud (water) is turned into ice particles (hail), charges are transferred owing to the reversal of charge polarity.
The reversal of the charge polarity also occurs when ice particles melt and turn into rain (water).
This is related to the occurrence of lightning.
2.1 Negative temperature polarity experiment
When the temperature of the soil increased, as shown in Figure 2, the voltage was gradually increased from −46.9 mV > −57.5 mV > −70.6 mV > −85.9 mV > −93.5 mV > −110 mV > −126.3 mV.
This shows that an electromotive force is always generated if there is a temperature difference, even in non-metallic materials.
Figure 2 shows the voltage was measured by increasing the temperature of the soil by using an electric heater.
As a result of this experiment, negative temperature polarity materials were soil, ice and stainless steel (Table 1).
2.2 Positive temperature polarity experiment
Figure 3 is a picture of the positive temperature polarity experiment (Water, Water obtained by melting snow, and Snow).
Experiment on positive temperature polar materials.
a) Water (850 mV) is drinking water; (b) Water (978 mV) is water from melted snow; and (c) Snow (864 mV) is snow.
However, Ice had a negative temperature polarity (Table 1).
This seems to be related to the bonding structure of H2O {(a) Water, (b) Water obtained by melting snow, and (c) Snow and Ice}.
2.3 Electromotive force measurements
Table 1 shows the experimental results of measuring the magnitude and direction of the electromotive force according to 16 types of temperature difference.
As shown in Table 1, in the case of soil measurement, the high-temperature side was charged negatively and the low-temperature side was charged positively. Therefore, soil is a negative temperature polarity material.
Ice had a negative temperature polarity (Table 1).
This seems to be related to the bonding structure of H2O {(a) Water, (b) Water obtained by melting snow, and (c) Snow and Ice}.