If you want to say that physics is the most difficult in middle school, I am afraid that in addition to mechanics, it is electricity. There are even many people who think that electricity is much more difficult than mechanics. Girls experience this more deeply than boys. For the vast majority of students, electricity is too abstract, and many concepts of electricity are invisible and intangible. For example, current, voltage, electric work, electric power, electric energy, etc., these concepts are non-visual in life, and too abstract knowledge is a cognitive difficulty for most people, not to mention junior high school students who are in contact with electricity for the first time.
Electricity is so difficult, how should middle school students learn it?
In addition to observing the daily circuits, electrical appliances, and various power sources around us, the most important method is to do more experiments, concretize abstract concepts through experiments, and at the same time deepen the understanding of the ins and outs of various electrical concepts and laws, and then consolidate and implement them by doing typical exercises.
In this process, in addition to paying attention to various precautions in electrical experiments, it is also necessary to learn to troubleshoot and judge circuit faults. Today we will summarize the general precautions of electrical experiments, as well as common circuit fault analysis!
1. General precautions for electrical experiments:
- 1. When connecting the circuit, the switch must be in the open state.
- 2. Before the switch is closed, check whether the circuit connection conforms to the schematic diagram, and then close the switch.
- 3. When connecting the circuit, it should start from the positive pole of the power supply and return to the negative pole.
- 4. When connecting the circuit, it is best to use the sequence of connecting in series and then in parallel, and finally connect the voltmeter in parallel at both ends of the resistor to be measured.
- 5. The connection of the sliding rheostat should be connected in series in the circuit in a "one-up-down" manner.
- 6. The ammeter should be connected in series in the circuit.
- 7. The voltmeter should be connected in parallel in the circuit.
- 8. All meter range selection adopts the "touch test method"!
- 9. The positive and negative binding posts of ammeter and voltmeter cannot be reversed!
- 10. Before the switch is closed, the sliding blade of the sliding rheostat should be adjusted to the maximum resistance!
2. Common circuit faults and judgments:
1. There is no indication of the ammeter: the ammeter may be short-circuited when the fault is possible, or the circuit is broken somewhere from the two binding posts of the ammeter to the two poles of the power supply!
2. The voltmeter does not indicate the number: the fault may be that the voltmeter has been short-circuited, or that it has been broken somewhere in the circuit between the two binding posts of the voltmeter and the two poles of the power supply!
3. The ammeter does not have an indication but the voltmeter has an indication and the indication is close to the power supply voltage: it can be affirmed that the circuit between the two terminals of the voltmeter and the two poles of the power supply is the path, so the cause of the fault may be the broken circuit of the electrical appliance under test or the voltmeter is connected in series in the circuit.
Of course, the related electrical experiment problems and circuit fault problems are ever-changing and varied, but they are always the same, and some knowledge is always the same.
More analysis and summary of physics mistakes in the high school entrance examination are summarized in the "Eight Sets of Physics Error Sets for High School Entrance Examinations", which includes almost all junior high school physics methods, skills, various common mistakes, easy mistakes, and difficult points, which are very practical and can quickly improve physics scores in a short period of time!