Junior High School Physics helps to organize and summarize a few knowledge points

Melting: Ice, steel into molten steel, candle burning and melting, ice cream, etc.

Coagulation: Water freezing, etc.

Vaporization: The water on the ground is dry, the vegetables are shriveled, and the "ha" on the glasses is gone.

Liquefaction: Haze on glasses, rain, dew, fog, "gas" on ice cream, smoke on stage, "sweat" on late autumn windows

Sublimation: The mothballs have become smaller, the filaments have become thinner, the frozen clothes in winter have not melted and dried outside, and the snowman that does not see the sun behind the building has become smaller.

Ninghua: Ice flowers, rime, frost, and the wall of the lamp are darkened, and iodine is sublimated in Ninghua first, so salt is put after stir-frying.

Vaporization (from liquid to gaseous) endothermy (raising one's own temperature) :

It is generally easier to vaporize at a higher temperature than the liquid, and it is better to dry clothes in a hot environment).

Liquefaction (from gaseous to liquid) exothermic (lowers its own temperature) :

Generally, it is easy to liquefy it at a lower temperature than the gas temperature] exhalation in winter, and the water vapor is easy to liquefy when it encounters colder air) dissolves (from solid to liquid) endothermy (increases its own temperature) :

It is generally easier to dissolve at a higher temperature than a solid temperature] Ice dissolves in water, if it is colder than ice, will it melt?

This involves the problem of not reaching the melting point of ice).

Coagulation (from liquid to solid) exothermic (reducing its own temperature) is generally easier to solidify at lower temperatures than liquids] Water condenses into ice, put a glass of water in the ice room, and it will freeze after half an hour, which also involves the problem of whether the water reaches the freezing point).

Sublimation (from a solid state to a gaseous state) endothermic (raising one's own temperature) generally occurs at any temperature (but not too much of an exaggeration)] Good example: mothballs in the closet. It's going to get smaller until it's gone, and so on.

Condensation (from gaseous to solid) exothermic (lowering its own temperature) is generally easier to condense at lower temperatures than gases] For example, there will be ice flowers on the window in winter; The formation of frost and so on.

Many students ask, "Is there a shortcut to learning physics?"The answer should be no, but you can only learn deeper physics knowledge after learning the basics of physics, and I have compiled some knowledge points of junior high school physics for your reference. Hope it helps.

Use of voltmeter:

1) The voltmeter must be connected in parallel with the electrical appliance under test;

2) The "+" binding post of the voltmeter is connected to the positive end of the power supply, and the "-binding post is connected to the negative end of the power supply;

3) Select the appropriate range (0 3V; 0～15v)。

The law of the voltage of series and parallel circuits:

1) The total voltage at both ends of the series circuit is equal to the sum of the voltages at both ends of each part of the circuit; (i.e. u-string=u1+u2).

2) The voltage at both ends of each branch of the parallel circuit is equal, which is equal to the power supply voltage. (i.e. u-and=u1=u2).

The resistance is represented by "r" and is in ohms, symbol. The resistance of a conductor is related to the material, length, cross-sectional area and temperature of the conductor. It has nothing to do with the voltage at both ends of the conductor and the current passing through.

Sliding rheostat:

1) Principle: Change the magnitude of the resistance by changing the length of the resistance line of the access circuit.

3) Function: Protect the circuit; Change the magnitude of the current in the circuit.

Ohm's Law. Ohm's law: The current in a conductor is directly proportional to the voltage across the conductor and inversely proportional to the resistance of the conductor.