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On junior middle school physics —— How to quickly judge the fault of the circuit
How to quickly eliminate circuit faults

Looking at the physics examination papers of senior high school entrance examinations all over the country in recent years, we can easily find that the frequency of judging circuit faults is still very high. Many students usually do this kind of problem, but the correct rate in the exam is still relatively low, and some reflect that they don't know where to start. The author helps students to summarize several common main judgment methods to solve this kind of problem:

"Symptom" 1: The electrical appliance is not working.

Diagnosis:

(1) If the circuit in question is a series circuit, see if other appliances can work. If all the appliances don't work, it means there may be a circuit break somewhere. If other appliances are still working, it means that the appliances are short-circuited.

(2) If the circuit in question is a parallel circuit, if all the electrical appliances don't work, the main circuit is broken; If other appliances are still working, it means that the branch where the appliance is located is open.

Symptom 2: The voltage represents zero.

Diagnosis:

(1) The circuit between two terminals of voltmeter and two poles of power supply is open;

(2) The voltmeter is short-circuited between two terminals.

Symptom 3: The current represents zero.

Diagnosis:

(1) There is an open circuit between the circuit where the ammeter is located and the loop formed by the two poles of the power supply.

(2) The resistance of the circuit where the ammeter is located is too large and the current is too small, so that the ammeter pointer hardly moves (if a voltmeter is connected in series in the circuit).

(3) The ammeter is short-circuited.

Symptom 4: The ammeter is burnt out.

Diagnosis:

(1) The circuit where the ammeter is located directly forms a loop between the two poles of the power supply, that is, a short circuit occurs.

(2) The range of ammeter is improper.