It s physics, and I didn t learn electricity well in the first unit of my junior high school.

wo doesn't quite understand.

That's how it should be.

The most common faults are short and broken.

Check the voltage with a voltmeter, measure the voltage of each electrical appliance, and find that there is a voltage of 0, which is short.

Check with a voltmeter, the amount of each electrical appliance should be 0, and suddenly one is the power supply voltage, which is broken.

It is more troublesome to use an ammeter to check for faults, because the ammeter has to be connected in series to the circuit. And the whole circuit is all in series, and the current everywhere is equal, and it is not good to measure. Generally, an ammeter is not used to check for series circuit faults.

If you have to use it, you can connect the ammeter in series to the main circuit and remove the individual consumers from the circuit. When the current of an electrical appliance does not change before and after dismantling, it is a short circuit, and if the current is from nothing, it is an open circuit.

Parallel circuit, the ammeter is connected to each branch separately, there is no current is an open circuit, and the parallel circuit is not allowed to short circuit, which will burn the power supply. Moreover, the parallel circuit fault is measured with a voltmeter, and it is basically impossible to measure it.

The electrical short-circuit is because the electrical resistance of the electrical appliance becomes very small, so that the current side of the circuit is very large! In general, the wire is in contact with the wire of the electrical appliance!

The main difficulty of physics and electricity in junior high school lies in the analysis of circuit diagrams and the use of various relationship operations.

If you want to learn junior high school electricity well, you need to 1. Learn to analyze the circuit diagram, and the current starts from the positive electrode and returns to the negative electrode, which is the most basic. If there is an ammeter and voltmeter in a circuit diagram, the meter method is used (the ammeter is regarded as a wire, and the voltmeter is regarded as an open circuit).

2. Find out the difference between the path (normal circuit), open circuit (the circuit cannot operate), and open circuit (directly connect both ends of the power supply, resulting in excessive current).

3. Write down the relevant formulas, such as: Ohm's law i=u r and its variants, Joule's law q=i rt, electrical power p=wt=ui

4. The relationship between voltage and current in series circuit and parallel circuit (series circuit: U becomes I unchanged and parallel circuit: I becomes U constant).

5. Learn to use the known quantities in the problem to find other values.

6. Find out the triboelectric uplift.

7. The resistance value of the fixed value resistor remains unchanged.

If you want to learn electricity well, you need to do a lot of problems until you are completely proficient in arithmetic, and in addition to that, you need to master general conclusions and phenomena.

During the exam: It is necessary to analyze the relationship between the circuit diagram and each value, and learn to use various formulas and their variations.

It's really hard to understand at first, take your time, first easy and then difficult, the circuit diagram will be easy later, just memorize the string of formulas that the teacher added.

Answer: First of all, you have to write down the formula, but not only to memorize, but also to be able to use more questions about the electricity part Practice makes perfect The amount of questions is enough, and when the time comes, you will know that you can use that formula when you look at the question and answer I also came here like this I remember that when I was in junior high school, I would not feel very difficult It would be good to brush up on the questions too much Junior high school physics is actually quite simple Come on (

Electricity is a very fascinating subject, and you can't live without it, because electricity can't be seen, heard, or perceived, and even many college students can't say, what is "electricity"? Therefore, learning must be synchronized with theoretical experiments, from shallow to deep, children can find a teacher with theoretical and practical experience to make up, or easy to understand, so that it is a wealth for the child's life.

If the power supply (battery) is the ideal voltage source according to the understanding of junior high school students, the output voltage is constant, and the internal resistance of the voltmeter is infinite, then the number of the voltmeter will be the same in these three cases.

However, the reality is not ideal. The battery has internal resistance, and the larger the current, the lower and higher the output voltage of the plexus. The internal resistance of the voltmeter is also not zero, so there is a measured current when the voltage is measured.

In the first figure, the voltage of the battery itself is measured.

In the second figure, because the resistors are connected in parallel, the output voltage of the battery is reduced, resulting in a large flow of electroosmotic reed dust.

The third figure should be that the contact at the wire lap is poor, the contact resistance is too large, although the measured current is not large, but it will also cause a large voltage drop, so the voltage value that can be measured by the voltmeter is significantly reduced.

This question should be explained clearly and has been brought to high school physics, because the dry battery you are using is too old, and the internal resistance of the chain is getting bigger.

If you redo more than one experiment with a new pair of batteries or a student power supply for the lab, it's clear that the positive voltmeter readings won't make that much difference.

When the output voltage of the power supply (battery) is constant, the voltmeter is open, so the indication of the voltmeter is the same in these three cases.

However, in fact, the battery has internal resistance, the larger the current, the lower the output voltage, and the voltmeter is not an open circuit, so when measuring the voltage at both ends of the electrical appliance, there will be current.

The first diagram is to connect the voltmeter to both ends of the power supply, which is to measure the voltage of the power supply. Tell Lee.

In the second figure, when the resistor is connected in parallel, the output current of the battery is relatively large, and the output voltage drop is low. Parallel connection has the effect of shunting.

In the third figure, when the wire has poor contact and the contact resistance is too large, the voltage that can be measured by the voltmeter will decrease.

Three steps 1, be able to analyze the connection of the circuit proficiently. Generally, it is connected in series and parallel. You have to analyze whether the electrical appliances and resistors used in series or parallel when a certain switch is closed and disconnected.

2. After analyzing the circuit connection, select the corresponding rules. For example, series connection: i=i1=i2 r=r1+r2 u=u1+u2 series voltage division, mutual influence, series resistance is greater than any of them, etc.

Parallel: i= i1+i2 u=u1=u2 1 r=1 r1+1 r2, parallel shunt, no influence on each other, parallel resistance is smaller than any of them, etc.

3. Know the definition and physical meaning of the concept. For example, the resistance is determined by the properties of the conductor itself, and by the conductor's own material, length, cross-sectional area, and temperature. There is also a regular use environment and so on.

In addition, pay attention to life, science and technology, major events, etc., which are often tested in the high school entrance examination, and in recent years, the test questions that only test electrical calculations in the high school entrance examination are almost non-existent!

The first of the three steps is the most critical!

Don't understand that place?

Carefully analyze each circuit, find out their characteristics, and after doing more, you will know what he wants to test you when you see the diagram, this method is very effective! Also, if you transform abstract thinking into an image, such as an electric current, don't think of it as an electric current, think of it as a group of small people in a queue ......Something like that.

If you don't understand that place, you can come and ask me

The big reason for the electrical problem:

1. Problem analysis is detached from circuit analysis.

2. Physical quantities are not well understood.

Memorize concepts and formulas, and find more precise questions to do.

Listen carefully in class, do homework in a timely manner, and consciously revise.

This, if you are in Shanghai, I can teach you.

I'm a high school physics teacher, so I'll give you a brief:

1. The physical whole is a kind of thought, which is similar to other modules as a whole;

2. The characteristic of electricity is that it can better correspond to the learning of physical objects, and it is easier for students to learn more in this aspect of electricity in life;

3. Even if you haven't observed too much before, it's best to calculate how many electrical appliances are used at home, how many kilowatt-hours of electricity are used in a day, and other questions, and you can even try to do some small experiments (such as after you calculate yourself, carry out the series and parallel connection of small electrical appliances), which will be more helpful.

It is easy to learn, because it generally only involves some common sense of life, and the question type is single, as long as you master the question type.

If you have a good teacher, you won't be afraid.

There are several chapters in Physics and Electricity for junior high school: Electricity and Circuits; Voltage & Resistance; Ohm's Law; electrical power; Home circuits. It's a step-by-step process.

If you don't learn any knowledge point well, it will be more difficult to learn later, as you said, it is not very clear to understand it in depth, even if you know the formula, you don't know how to apply it. For example, when learning about current and circuits, the knowledge of the book is fully understood, but the knowledge that is not in the book is not very clear when drawing the real circuit diagram according to the circuit diagram, drawing the circuit diagram according to the actual diagram, designing the circuit diagram, and drawing a very complex circuit diagram in series or parallel.

After learning the ammeter, when looking at the physical map, the ammeter is to measure whose current, when the ammeter has an indicator, and when the ammeter has no indicator, all of which need you to understand and master. When learning voltmeter, the voltmeter measures the voltage at both ends of the wire, what will happen to the indication, what will happen to the bulb when the voltmeter is connected in series with the bulb, etc. When learning Ohm's law, the equation should be applied with attention to identity and simultaneity.

Ohm's law states that the current is proportional to the voltage, and it is wrong to say that the voltage is proportional to the current, etc. The difference between actual power and rated power, what exactly does the brightness of the bulb depend on. How each component in the home circuit is connected, etc.

The above knowledge points are not clearly written in the book, and most of them are explained by the teacher and need to be understood by yourself. There are too few knowledge points in the textbooks, and the knowledge in the supplementary books is not necessarily gradual.

To learn electricity, understanding is the most important, and it is best to do experiments by yourself, you can go to the teaching instrument station to buy some experimental equipment: batteries, bulbs, ammeters, voltmeters, wires, switches, sliding rheostats, etc. Which one won't be, which diagram can't be understood, actually assemble it, take a look at the effect, the memory is very deep, and then ask the teacher why it is like this.

Another thing to add is that interest is very important, when you answer a difficult question yourself, you will be excited, and with praise from teachers and parents, you will be interested. , is my QQ, if you have any questions, you can ask me, you can also know.