How to learn questions such as science circuits in junior high school

1。Be proficient in converting circuit diagrams with physical diagrams, and convert physical diagrams into circuit diagrams before solving problems.

2。Remember the characteristics of voltage and current of series circuit (u=u1+u2)(i=i1=i2)(r=r1+r2)(u r=u1 r2=u2 r2), and the characteristics of voltage and current of parallel circuit (u=u1=u2) (1 r=1 r1+1 r2) (i=i1=i2).

There is also the universal formula i=u r and the deformation of the formula, but keep in mind that this formula can only calculate the resistance, but it does not mean that the magnitude of the resistance changes with the magnitude of the current or voltage, that is, the magnitude of the resistance has nothing to do with electricity and current.

3。Because the resistance of the voltmeter is very large, the current passing is very small, so the voltmeter is regarded as a disconnected circuit, and the resistance of the ammeter is very small, so it can be regarded as a wire, so the ammeter can not only be connected to the battery and the voltmeter can.

4。There is a ratio between the effective length and the effective resistance of the sliding rheostat, which can be used in calculation problems.

Although this unit is a little difficult at the beginning, as long as you listen carefully in class, it is not difficult to skillfully apply it to understand the formula, I am also a sophomore junior high school student, the calculation questions are not difficult, do more practice, sometimes the "sea of questions tactics" is also king.

1.Understand series and parallel circuits and their composition.

2。Understand what switches, slide resistors, fixed value resistors, small bulbs (loads), etc., do.

3。Understand the relationship between voltage, resistance, and current.

4。Voltmeter, ammeter, multimeter (resistance measurement, etc.) will be used.

5。Different materials of wires have different resistances, which will be calculated.

I'm basically doing waterways properly to learn, but there are a small part that you don't need to pay attention to, you can try it.

Do all the experiments in the book seriously, and think about the things around you that use it.

Three magic weapons to improve the physics score of the middle school BAI exam.

First, grasp the basics

Clause. Second, heavy experiments.

Clause. 3. Break through the difficult DAO

1] The basic knowledge is specialized.

The eternal theme of the high school entrance examination is to strengthen the understanding and memory of basic knowledge, establish a basic knowledge network in the brain, and oppose rote memorization!

1. Basic knowledge includes: basic concepts (definition), basic laws (laws, principles), and basic methods;

2. Criteria for understanding: What is it that each concept or law can answer? How? Why? Able to use the concepts, laws and methods learned to solve some specific physical problems;

2] Experimental questions have a large score, easy to get and easy to lose, and we should attach great importance to all experiments in sound, light, heat, force, and electricity, 1. To know "what to do?" On what basis? How? ”；

2. Be proficient in the use of various experimental equipment, use rules, functions, and precautions;

3. Pay attention to the arrangement sequence and number of experimental steps (** regular six times, general measurement three times);

4. It should be narrated in physical language;

5. Be able to design**, read**, and fill in**;

Three] break through the difficulties, break through the difficulties must master the methods and skills, must not be brute, brute and laborious, time-consuming and ineffective, but also make yourself lose confidence, let alone engage in the sea of tactics, you must know that it is difficult to master their laws (force, electricity), find ways and skills to solve them, and there is no problem in the high school entrance examination.

Electricity is the most important.

The reply is to recognize the electricity.

Circuit structure, local short circuit can accurately judge the white to, the general junior high school electrical problem circuit structure is related to the local short circuit, after identifying the circuit to draw the equivalent circuit diagram, to further judge the relationship between voltage, current and resistance Annotation conditions, an experienced teacher usually asks you to mark the known conditions in the problem on the diagram when you come into contact with electricity.

Pay attention to the correspondence, current, resistance, electric power, which electrical appliances are used separately, to be clear, in order not to be confused, you will mark in the subscript, with p1 p2 p total and the like to make yourself clearly marked.

There is not much content in junior high school physics and electricity, and it is not difficult to learn this content well, the most important thing is to.

DAO mastered the basic laws and formulas of current return, voltage, electrical resistance and electric power, especially formulas, and needed to be familiar with the basic formulas and their deformations, and these laws and formulas are not many.

Generally speaking, the method and skill of doing the problem is the reverse deduction method, which is to find the quantity to know according to the formula of the quantity sought, if it is satisfied, it can be found directly, if the quantity to be known is not known, it can be found according to another formula related to the quantity, and so on, it can generally be solved. (The more difficult part of this is mainly related to electrical power).

It's not difficult, the main thing is to memorize formulas and theorems. Observe electrical equipment at the same time.

It depends on what angle you look at it, it's all basic, and it's not difficult.

1. Firmly grasp the basic knowledge, including principles and formulas, especially Ohm's law formula, electric work and electric power formulas (including their extended formulas), and the characteristics of series-parallel circuits.

2. Practice more and summarize some problem-solving ideas by yourself in the exercises. Analytical Methods for Dealing with Changing Circuits:

1.Draw the circuit diagram according to the different conditions of the circuit, and simplify the circuit (remove the disconnected or short-circuited, the ammeter is equivalent to the wire, and the voltmeter is equivalent to the disconnected). 2.

According to the circuit diagram of different situations, combined with the characteristics of series and parallel circuits, the relationship between the current, voltage, resistance, electrical power and power supply voltage and other physical quantities of each electrical appliance (or resistance) is analyzed. 3.Compare various situations, judge or analyze the changes or relationships of voltage, current, resistance and power of various electrical appliances (or resistances) under different circumstances.

Generally speaking, if the power supply is not changed, the total voltage of the circuit does not change; In general calculations, when the voltage changes little, the change in resistance of each electrical appliance is negligible. During the movement of the sliding blade of the sliding varistor, the change in resistance is analyzed according to its wiring.

can be listed (don't have two unknowns), that's pretty much it. If you know it's useless, you must ask me to come over like this, if you want to learn physics well, you have to buy a reference book and read more Pay attention to transformation,

Hehe, this is simple, first of all, explain that there are two breakpoints, don't understand it as one, think about whether a wire is broken and there are two heads, hehe.

Let's explain the meaning of this sentence again.

The electric pen is used to detect the live wire, the live wire phase will produce 220V voltage when the neutral line, you put the electric pen touch at the position of the live wire when the neon tube of the electric pen will glow, because we are standing on the ground, the voltage of the earth is 0V and the voltage of the zero line is the same (in fact, the zero line is a wire taken out of the earth, and a metal block is buried in the soil to lead out of 1 wire on it), which shows that the live wire forms a current circuit through the electric pen and our body, Because there is a large cement resistance in the pen, almost no current flows through our body, so we will not be electrocuted, and we are equivalent to providing a neutral line to the neon tube of the pen; If you want to measure the zero line, the zero line and our body itself is a wire, there is no voltage, 0v minus 0v is not still 0v, hehe, it's really simple. Got it.

The second is that the live wire is open or the filament is broken, and the neon tube of the electric tester can be luminous between the break point and the live wire, and the neon tube of the electric pen can not be luminous between the break point and the neutral line; This is not true. Whether it is the live wire broken or the zero line is broken, you can use the electric tester to measure, the result is that one end of the breakpoint glows, one end does not emit light, the live wire is broken to understand, when the zero line is broken, because there is no current, the voltage of the live wire after passing the load is also the mains voltage, so it can be measured with the voltage tester. Sometimes both ends of the side light port of the tester are on, but the bulb is not on, which means that the zero line is broken.

If the filament is broken, it means that one end of the lamp port is on, and the other end is not.

First, the fuse is blown out, not a short circuit, but an open circuit, also called an open circuit. Regarding the question you asked First of all, you should know that the live wire is the end of the high voltage, which is equivalent to the power supply, and the current flows in from the live wire, so it can be a neon tube to emit light. The neutral line is only used as a line, similar to a pipeline, and there is no voltage.

1.Understand series and parallel circuits and their composition.

2。Understand what switches, slippery pants resistors, fixed value resistors, small bulbs (loads), etc., do.

3。Understand the relationship between voltage, resistance and current.

4。Voltmeter, ammeter, multimeter (resistance measurement, etc.) will be used.

5。Different materials of wires have different resistances, and they will calculate the nonsense.

This question selects option A, the first option is used for the circuit is a parallel circuit, and the electrical appliances do not affect each other. So, if you want to change the brightness of the bulb, this option can't be changed.

The second option can be changed. When the switch is closed, the power supply voltage is all added to the bulb, and when the switch is disconnected, the power supply voltage is shared by the bulb and the resistance, so the brightness of the bulb will also be dimmed. Therefore, the second option is completely possible to change the brightness of the bulb.

The third can also change the brightness of the bulb, because after entering the sliding rheostat, by changing the compound words of the sliding rheostat, then the brightness of the bulb can also be changed.

The fourth option is even more good, because change the voltage of the battery. One battery for a while, two batteries for a while, then the brightness of the bulb can also be changed.