Nine up and nine physics knowledge points, the more the better, the more detailed the better, thank

There are nine physics knowledge points

1. Gases, liquids and solids can all diffuse. The speed of diffusion is temperature dependent. The diffusion phenomenon shows that the molecules of all substances are in a never-ending irregular motion, and indirectly proves that there is a gap between the molecules.

2. Interaction force between molecules: there is both gravitational force and repulsive force, and gravity and repulsion force exist at the same time.

3. When the distance between molecules is very large (more than 10 times the diameter of the molecule), the interaction force between molecules becomes very weak, and it can be approximated that there is no interaction force between molecules.

4. Thermal motion: The irregular motion of a large number of molecules inside an object is called thermal motion. The speed of the irregular motion of the molecule is related to the temperature, the higher the temperature, the faster the irregular motion of the molecule, and the lower the temperature of the object, the slower the irregular motion of the molecule.

Internal energy is also often referred to as thermal energy.

5. Specific heat capacity: The ratio of the heat absorbed by a certain mass of a certain substance when the temperature rises to its mass and the product of the increased temperature is called the specific heat capacity of the substance, referred to as specific heat. The specific heat capacity is indicated by the symbol c.

This problem mainly requires that when the sliding rheostat slide p is adjusted within this range, the current through the two ammeters does not exceed its range.

In this way, we first figured out which line the ammeter A1 and A2 measure the current on each line.

From the circuit diagram, it can be seen that A1 is connected in series with R1, and the current I1 through the branch of R1 is measured.

The ammeter A2 is in a dry circuit and measures the total current i of the circuit.

R1 = 20 , U1 = U = 10V, the current through the ammeter A1 i1 = U1 R1 = 10 20 = will not exceed.

If the current i through the ammeter A2 does not exceed 3a, then i=u r

r=u i=10 3=3 and 1 3

That is to say, the total resistance cannot be less than 3 and 1 3. The total resistance is formed by the parallel connection of R1 and R2, according to the relationship between the total resistance of the parallel circuit and the sub-resistance, R=R1R2 (R1+R2), that is.

3 and 1 3=20r2 (20+r2).

10/3（20+r2）=20r2

20r2-10/3r2=200/3

50/3r2=200/3

r2=200/3×3/50=4（ω）

To make the total resistance r not less than 10 3, by calculating r2 can not be less than 4. Therefore, the resistance range of the R2 access circuit is 4 10.

w=uit=3v*

p=ui=3v*

2.The same resistance does not indicate the same rated current, but the same rated voltage necessarily indicates the same rated current.

1.Because w=pt

And because p=ui

So w=uit=3v*

p=ui=3v* Because it is two dry batteries, one battery.

2.To normalize the luminous voltage, it is enough to reach the rated voltage, so B is right.

Solution: (1) m winter = 1v1 = points).

m summer = 2v2 = points).

In winter**: 55 yuan kg (1 point).

In summer, ** is: 51 yuan 12kg yuan kg (1 point) so: high in summer**.

2) If the two seasons are the same, that is, the summer ** is RMB kg, then the price of each bottle in summer is: 55 yuan (2 points).

Answer: (1) It is calculated that the summer ** is high.

2) In order to make the summer ** the same as the winter **, the price of each bottle in summer should be 50 yuan (3)** is 55,167 yuan.

The balance has been adjusted, which is weighing, not the nut. Left object right code, pointer to the left, should add weights to the right disk, not [the quality difference between the two sides is less than the minimum weight, at this time the pointer deviation is very small] to move the code. ）

The balance is not adjusted, which is during the leveling phase, when the pointer points to the right and the balance nut is adjusted to the left. ）

Whether the balance is adjusted depends on whether there are objects and weights on the balance at this time.

1. Answer: D.

The reason is that the balance nut is not required and cannot be adjusted when weighing the object, and the answer is ab.

When weighing an object, the object is placed on the left disk of the scale, the weight is placed on the right disk of the scale, and the pointer is biased to the left of the index dial, indicating that the weight mass is less than the mass of the object. It is necessary to add weights to the right disc or move the yard to the right. So the answer C is wrong and D is correct.

2. It is about the balance adjustment before use.

The pointer is offset to the right of the index dial. Explain that the right side of the balance is heavier, and the nut at the right end should be adjusted to the left, and the answer B is correct.

Answer A is in the wrong direction.

Answer: CD is the wrong practice, when the balance is adjusted, the code should be placed in the 0 scale position on the scale, not moving.