Using voltmeter and ammeter to measure the resistance of small bulb when it is normally emitting, what problems should be paid attention to

Using voltmeter and ammeter to measure the resistance of small bulb when it is normally emitting, what problems should be paid attention to

The main thing is to see how you connect the ammeter and voltmeter in series or in parallel

If the resistance of a bulb is 10 Ω and the voltage is 4.5 V, which range of voltmeter and ammeter should be selected for accurate measurement

The range of voltmeter is 0-10V, the range of ammeter is 1a. I don't know if there is such a meter. Generally, the pointer should be in the middle of the dial
Now use electronic automatic range, mechanical basically no, test electrician or use pointer meter

As shown in the figure, it is an experimental circuit for a student to measure resistance. When the switch is closed, the pointer of ammeter and voltmeter is slightly deflected. The reason for this phenomenon may be ()
A. Short circuit of sliding rheostat B. open circuit of setting resistor C. larger resistance of setting resistor D. larger resistance of sliding rheostat connected into circuit

A. If the sliding rheostat is short circuited, the voltage at both ends of the setting resistor is the power supply voltage, and the indication of the voltmeter should be 3V. So a is wrong. B. the setting resistor is open circuit, the circuit is disconnected, the circuit current is 0, and the pointer of the ammeter and the voltmeter does not deflect, so B is wrong. C. The setting resistor is large, and the setting resistor should share most of the voltage. The voltage indication is large, so C is wrong The resistance of the rheostat connected to the circuit is large, resulting in small current through the circuit, so the pointer of the ammeter and voltmeter are slightly deflected, so D is correct. So D is selected

In a series circuit, a voltmeter measures the voltage at both ends of a small bulb. If the ammeter and the voltmeter exchange positions and close the switch, what will happen?

It seems to be junior high school physics ah, ammeter is equivalent to short circuit (can be replaced by a wire), voltmeter (internal resistance is very large) is equivalent to short circuit (that is, this road is blocked ah), after changing the position, ammeter and bulb in parallel (bulb does not light, there is no voltage at both ends), the total result is equivalent to ammeter and voltmeter in series and then connected to the power supply