Physics in the second year of junior high school, electricity board, fast, how to learn physics and

In the circuit they designed, the range of the ammeter should be 0 and the sliding rheostat should be c.

The reasons are as follows: because the maximum current is i=u r=4 7=, it is better to use the range of 0 in the ammeter;

Because the resistance to be measured is between 7 and 9, if a 500 sliding rheostat is selected, not only is the current too small to read, but also the current change is too small when the switch is connected to both sides of A and B, and the change cannot be observed. The slip C is about the same size as the resistance to be measured, which avoids the occurrence of the above situation. Therefore, the sliding rheostat is selected C

The steps should be changed to: throw the switch to B, keep the sliding position of the sliding rheostat unchanged, make the pointer of the ammeter point to another appropriate position on the dial, and read out the indication of the ammeter after the circuit is stabilized (denoted as I2).

The reason for this: because the resistance used in the sliding rheostat cannot be read. Only in this way can the system of equations be set to find the value of the resistance to be measured.

rx=u(i2-i1)i1i2+r0

The derivation is as follows: Assuming that the actual resistance of a sliding rheostat is r, according to Ohm's law, there are two cases respectively:

u=i1(rx+r) ①

u=i2(ro+r) ②

：i1/i2=(ro+r)/(rx+r)

Substitute for :

u=i2[ro+(i2ro-i1rx)/(i1-i2)]

rx=u(i2-i1)i1i2+r0 .

The reward is not proportional to the value of the question answered.

It is not difficult to elaborate on the detailed process, but the code words are too troublesome, and I lack motivation.

The picture was eaten by you? Also, are you a little stingy? Do you know how many words you need to code for this question? The first question is good, but the second and third questions are a big one! I'm waiting for you to add points!

Put the diagram up, I'll make it for you, I'm too lazy to find the diagram myself.

Did you study electricity in the second year of junior high school? What grade did you start studying physics? But I can start with the third year of junior high school.

Electricity and work are important knowledge points in the third year of junior high school, and electricity is both the key and the difficult. The first point: mainly to figure out the two ways to connect the circuit:

Series, parallel.

The second point is to correctly understand the main uses of ammeters, voltmeters and sliding rheostats.

Point 3: That's the point! Understand and become proficient in Ohm's law, understand the relationship between current, voltage and resistance and the related calculations.

The main takeaways are divided into three main points. 1. The development of Oersted, that is, the magnetic effect of electric current, mainly understands its definition, the structure of electromagnets, the factors affecting the strength of magnetism and related applications. 2. The effect of magnetic field on electric current is mainly generator.

If you understand its definition, structure, role and principle, you will know how to use it. 3. Electromagnetic induction phenomenon. Mainly for generators, understand their definition, structure, function and principle.

The most important thing to learn physics is to memorize the main definitions of knowledge points and understand the uses of physics. And skillful in the knowledge of physics.

I wish the landlord a happy study.

Why is electricity a headache for so many people? Because electricity is relatively abstract, some problems can only be imagined, and circuit diagrams have high requirements for thinking skills, so many people fall into the pit.

First of all, you need to do a good job of pre-studying, understanding the basic concepts, such as the meaning of electricity, especially the circuit diagram to read several times.

When you are in class, you should listen carefully to the class, especially when the teacher is doing experiments, you should study seriously, and you can also ask the teacher to borrow experimental instruments to do experiments for you after class, so as to enhance your practical ability.

Do more exercises, although the tactics of the sea of questions are not advocated, but the science subjects need to be practiced more, so that they can be more flexible. Remember, it is very important to preview and summarize, after the preview, do the questions yourself, and then summarize some methods, such as what is the reason why the light bulb does not light up, you should memorize it, because you often take the test, and you also know how to measure.

Believe in yourself and don't be discouraged, it's not hard now. It's not until you're in the third year of junior high school that you learn about electricity, and you don't have to think about it if you don't drive you crazy.

As long as you do a good job of pre-studying, it is not so difficult to summarize often, and it is better for you to be one or two lessons ahead of the teacher.

First of all, we must memorize the formula clearly, close our eyes, and all of them must be able to be connected to form a knowledge system. The teacher should be clear about the concepts during the lesson. Of course, this is only theoretical, in practice you have to do more questions, you can also buy a special book on physics and electricity in the third year of junior high school, you must not ask the teacher or classmates if you can't do it, buy a notebook, take the teacher's class notes on the front, and remember the wrong questions on the back Good question, this wrong question is when you surpass others, when others don't know where to start reviewing for the final exam, you can take out the notes to see the wrong questions, know that you have a problem in that link, so as to check and fill in the gaps, and greatly improve learning efficiency, Because when you do the questions you do the first time, you can do them the second time, and the questions you can't do the first time may not necessarily be able to do them the second or third time.

Memorize the content of the formula, the conditions for application, find out the connection between the formulas, and make yourself more proficient by doing more exercises.

In fact, the electricity part is the best to learn, compared to mechanics or something is the best to learn, you just need to memorize more formulas, and then do more exercises, don't know how to ask the teacher, take the class seriously, it's okay

Just take apart the lights at home and take a look at them.

Whether the several fluorescent lights in the classroom are connected in series or parallel.

Read the textbook at least 3 times, and think new about it every time you read it. When listening to lectures in class, you should diverge your thinking and be able to associate!

Make reasonable use of your time.

Make a note of the formula.