A physics problem in the second year of junior high school, help me explain!

Obviously, if the air is dry, that is, the water vapor content is less, the water evaporation rate is faster, and the wet cloth evaporates more water and absorbs more heat, so the difference between the two thermometers is large.

This question is just a little more turning, you can figure it out if you analyze it slowly and think about it slowly.

Life example: When the weather is dry, clothes are easy to dry, which means that the water evaporates quickly, the evaporation per unit time is large, and the water evaporates and absorbs heat, so the cooling, the more evaporation, the more cooling, that's all.

Look at the upstairs.,It's too professional.,The landlord is only in the second year of junior high school.,The diffusion department has come out.,It's scared to death.,How easy to understand me.,Embarrassment.。

The lower the amount of water vapor in the air, the faster the water will evaporate. The thermometer wrapped in a damp cloth absorbs heat when the water evaporates, and the lower the air humidity, the smaller the indicator. The thermometer without a damp cloth shows the correct air temperature.

So the greater the difference between the two thermometers, the lower the humidity, which means the lower the amount of water vapor in the air.

— This is the principle of a hygrometer in reality. The one wrapped in a damp cloth will take away the latent heat due to the volatilization of moisture, so the temperature is lower. The other one without a damp cloth is of course higher than this one.

When the outside humidity is smaller (that is, the lower the water vapor content), the faster the moisture evaporates with the damp cloth, of course, the faster the temperature drops, the lower the indicated temperature, that is, the greater the difference between the number of two thermometers; On the contrary, when the outside humidity is very high and large to saturated humidity, that is, when the relative humidity is 100%, the wet cloth you wrap can no longer volatilize water, so the instructions of the two thermometers tend to be the same, that is, there is no difference.

This should be related to the concept of molecular diffusion in physics.

Encyclopedia diffusion. The rate of diffusion is directly proportional to the concentration gradient of the substance. In other words, the lower the water vapor content in the atmosphere, the faster it spreads, that is, the faster it evaporates.

Hope it helps.

Voltage is the difference in potential between two points in a closed circuit, which can be compared to the voltage by the pressure difference of water.

The water pressure difference pushes the water from high to low, and the voltage pushes the current from the positive to the negative.

There is no voltage in the appliance itself, and there is only a voltage at both ends when it is used, and there is always a certain voltage between the positive and negative poles of the power supply, so I think it is to choose A and C

The work done by the lever to overcome gravity is: w1 gh=196n x

The power does work on the lever, without considering friction: w2 w1

The magnitude of the power is: f w2 s from the formula w2 fs

The work done to overcome gravity is equal to g*x=196n*

The work done by the kinetic force on the lever is converted into the work done by the lever on the object.

3:98n is obtained from the size of the arm that is inversely proportional to the force and the direction of the power is straight downward.

1、e=mgh=gh=196n×

2. All the work done by power is used to overcome gravity, so it is also.

3. E=fs, then f=e=s=

The lever overcomes gravity to do work ( )j, the power does work on the lever ( )j, and the magnitude of the power is (98)n