Time is like an arrow, the sun and the moon are like shuttle!In a blink of an eye, only seven months left next years middle school entrance examination!The ninth grade learning task is very heavy and the time is very tight. At this stage, junior high school students may be a little slack, and they may be with the ideal high school!
The most important knowledge module of the ninth grade physics and the highest score in the middle school entrance examination is -electrical!
All the electrical knowledge from the beginning to the end is actually very systematic, and the types of question involved are relatively fixed. In general, there are so many. Therefore, if you want to learn electrical, onlyTo understand and firmly grasp all knowledge and methods and laws, do more questions, more research questions, and summarizes, and can smoothly solve the electrical module!
Today, we take the experimental title of a nine onto the physical electrical experiment as an example to study the relevant questions and see what knowledge and methods need such questions!
Look at this experimental question:
This experiment is "Inquiry currentThe relationship with voltage and resistance ", regarding this experiment, most junior high school students painting light road maps are okay. All ninth grade students who study carefully should be very familiar with this circuit diagram because this circuit diagram still appears inIn the experiment of "measured resistance" and "measurement of electricity".
It should be noted that (2) Some students are filled in 2.6, 0.26, which is very unsatisfactory.Wrong, dont read these two numbers!Later, I asked that this part of the students did not read the number of exponents, but the data based on the form, and they felt that the difference between the two adjacent sets in the form of the form was 0.2 and 0.02, so they got these two two.Error data!They did not take a closer look or think about the value of the existence of Figure 2 when they tried the questions!Its surprising and regrettable!
The most worthy of all the students attention and attention is (3), the scoring rate of this question is extremely low!Almost the whole army is covered!Because most of the usual experimental questions are mostly a straight line that draws vosus images through drawing points, and the image drawn as a straight line with an over -coordinate original point, so that the current is proportional to the voltage.Students write conclusions, and rarely see how the conclusion is derived. Therefore, many students wrote that more students wrote "the larger the voltage, the larger the current"!They all forgotten that the teachers reasoning method of judging the positive and negative proportions through data judgment by data when explaining such positive ratio.In fact, only the relationship between the positive and negative proportional function in mathematics can be concluded: "When the ratio of the two variables is a fixed value, the two are proportional";In contrast "!Students must keep in mind this method, and there will be no problems when they encounter such questions in the future.
About (4), when the fixed value resistance is replaced with a large resistance, we should immediately think of "change the big tone", that is, change to changeAfter the large resistance, in order to maintain the voltage of both ends, the resistance value of the sliding resistor needs to be increased!However, according to the series of pressure division, the maximum resistance of the sliding resistor is too small. What should I do?You only need to connect a resistor in series to the sliding barrier. This resistance can be divided into a part of the voltage, which can make the voltage of the sliding resistor smaller. Therefore, even if the maximum resistance of the sliding resistor is small, it can also make the fixed value resistor when its change.The voltage at both ends is maintained at 2V.If you choose A, because the power supply voltage is too large, the sliding resistor resistance value is too small. According to the series voltage, it can be seen that the voltage ends of the fixed -value resistance will always be greater than 3V, and it will never reach 2V, so it is not correct.
Through this question, it can be seen that you must not remember the hard back physical knowledge.At the same time, we must pay attention to summary, study more wrong questions, and improve physical results in the summary!
