Urgent!! What is a physical phenomenon? Urgent!! Which physics expert is here to help me?

The so-called physical phenomena are called "things" on the earth, and the inherent properties of "things", or the properties that we have not discovered or have discovered in themselves, are called "principles". If it is chemically speaking, the breaking of the old chemical bond and the formation of the new chemical bond change the properties of the object itself, so in a real sense. To determine whether it is a physical phenomenon, in the final analysis, it is to judge the chemical bond.

Macroscopically speaking, it is to see that this reflection is the generation of new substance, that is, the substance that was not present in the original reactant. Physical phenomena do not generate anything new, ice, water, and water vapor are all H2O. Therefore, the criterion for judgment is "making something out of nothing".

The only special one is the "flame color reflection", which is combusting, but this is a physical reaction. Absolutely original, hopefully !!

Physical phenomena are manifested by changes in the external structural properties of matter (e.g., height, velocity, temperature, electromagnetic properties, shape), but all natural or man-made phenomena except for changes in the essence (e.g., molecular structure, chemical properties, etc.).

Physical phenomena are the phenomena that you see in physics experiments or in physics. Such as the "white gas" seen when boiling water; The change of the number of meters and the increase, decrease or unchanged of the number of thermometers are all physical phenomena.

Physical phenomena refer to the change of the form, size, structure, and properties (such as height, velocity, temperature, and electromagnetic properties) of matter without the formation of new matter.

1) In order to ensure that the induced current is not generated in the MN rod, the magnetic flux of the closed circuit must not change;

2) magnetic flux 0= t=b0s0=b0l2;

3) When the metal rod Mn moves at a constant velocity to the right along the frame with velocity V, the area of the rectangular region Mden is: S=L(L+VT);

4) Since S increases with time, it can be seen that B gradually decreases with time;

5）ф0=b0s0=b0l2=фt =bs=b l（l+vt）；So, b= b0 l (l+vt).

Solution: In order for no induced current to be generated in MN, the magnetic flux of the closed circuit composed of DENM must be constant, i.e.,

bs=b0l^2

s=l^2+vtl

Coupling: b=(b0l 2 l+vt).

1.There is no air or very little air in the place where the suction cup is in contact with the glass, causing the air pressure on the top of the glass to be less than that below, and the resultant force of the air pressure received is upward, canceling out the gravity.

Density * volume = cubic kilogram cubic meter * 1 * nN.

3.The size is the pressure difference between the air below and the air above, so g = p * s = 1 * 10 to the 5th power * 8 * 10 negative cubic square meter = 800 N that is, 80 kg.

1/1, that is, the air pressure in the washing dish only needs to be 3/4 of the outside, so that the difference from the opposite lower part is 1/4. So little Pa.

d right. When the power supply is turned on, the current in the coil increases, and the magnetic field generated gradually increases, and the gradually increasing magnetic field produces an electric field (Maxwell's electromagnetic theory). At the circumference of the sphere, there is an annular electric field, and the ball is charged and is subjected to the electric field force, which will cause the plate to rotate.

From this analysis, the ball is electrified.

Since the specific direction of the current in the coil is not known, the chargeability of the ball cannot be determined. So, option d right.

I choose D, and I understand it this way: If the coil produces an upward magnetic field, then the metal ball must produce a downward magnetic field, and according to the right-hand spiral, the ball is positively charged clockwise.

For example, if the coil produces a magnetic field that goes down to Bu, then the metal ball must produce an upward magnetic field, and at this time, it is clockwise according to the cavity touching the right hand spiral rule, and the ball can be negatively charged.

Let's choose D. First of all, the rotation of the disc must be forcefully generated, so the source of the land c answer is excluded.

Since the polarity of the magnetic field generated by the coil is uncertain, the affirmative answer will be removed from the hail, excluding ab,

Analysis: Only when the steel ball is charged will it have a strong effect in the magnetic field. is the force experienced by the charge in the macro magnetic field.

This takes into account the relationship between surface tension and polarity.

The bowl and the water are polar, so the water can be sucked on the bowl, and evenly distribute the water is polar, the oil is non-polar, when the oil surface in the soup is blocked by water, the two pieces of oil will not break through the water, everyone repels each other, and the oil can be melted together after breaking the water film with chopsticks.

You can look at the contact point between water and oil, and the oil is concave, which means that it is repulsive; When the bowl is connected to the water, the edge of the water is extended, indicating that they attract.

It's all the action of surface tension.

1) On a clean bowl, the adhesion of water on it is uniform, and due to the action of surface tension, small water droplets will be evenly distributed.

2) If the oil flowers on the soup are not subjected to external force, they will maintain their own oil flower shape due to the action of surface tension;

As soon as another oil splash is encountered, it will melt the two parts into a new oil bloom because of the action of surface tension.

1.The water indicates tension and converges into droplets, which are distributed on the surface of the bowl.

2.Water will wrap around the oil, and the water will have tension and will wrap around the oil. It won't fit in at first.