When the voltmeter measures the voltage, the voltage of the two dry batteries is exactly 3V, and the two ranges of the voltmeter are 0 ~ 3 and 0 ~ 15. Which range should be selected?

When the voltmeter measures the voltage, the voltage of the two dry batteries is exactly 3V, and the two ranges of the voltmeter are 0 ~ 3 and 0 ~ 15. Which range should be selected?

3V, because the wire will lose a small part of the voltage, so the voltage indication is less than 3V

Xiao Ming has a standard voltmeter with two ranges of 0 ~ 3V and 0 ~ 15V
When it is used to measure the voltage of a battery pack composed of two dry cells in series, the wiring is correct, but the reading he reads is 10V, which is obviously wrong
What is the reason for his mistake?
2. What is the actual voltage?

Wrong reading range
It should be 2V

The following equipments are available: two dry batteries, ammeter (0 ~ 0.6A; 0 ~ 3a), voltmeter (0 ~ 3V; 0 ~ 15V), sliding rheostat (10 Ω 1.5A)
）Please use these devices to measure the rated power and current of a small bulb (rated voltage 2.5V, rated power less than 1W)
(1) According to the requirements of this experiment, use stroke line instead of wire to connect the equipment in figure (a) into a physical circuit (pay attention to the selection of the range of the ammeter, do not cross the wires), and draw the corresponding circuit diagram (this problem can not draw a diagram, just talk about the range of the voltmeter and ammeter)
(2) After closing the switch, adjust the sliding rheostat so that the voltage indication is v. at this time, the ammeter indication is as shown in Figure 5 (b), then the current is a
(3) According to the experimental data, the rated power of the small bulb is w and the resistance is Ω
(4) If a student makes an error when connecting the physical circuit, it is found that no matter how to move the slide of the sliding rheostat, the sum of the ammeter and the voltmeter will not change, and the light of the bulb is dark, the possible cause of the error is
Note: (2), (3) questions need detailed process, thank you!
Figure B in the second question is the pointer I mentioned above, which means that the small range is 0.48 and the large range is 2.4
I know the answer
(2 ) 2.5 0.26
(3 ) 6.5 9.6
(4) two terminals of sliding rheostat are connected below
But I don't know the process of (2) and (3), the key is the process!!
To give you the answer is to help you answer. O(∩_ Thank you

Let me talk about it one by one
(1) The purpose of the experiment is to measure the rated power of the bulb, so we must adjust the voltage to the rated voltage when measuring, so the range of the voltmeter is 0 ~ 3V. There is another condition in the title, which says that the rated power is less than 1W. According to P = UI, we can get I

Three dry cells are connected in series to supply power to a resistor of about 10 Ω. To measure the voltage at both ends of the resistor and the current passing through it with a voltmeter and an ammeter, the selected range is ()
A.15V,0.5A
B.15V,3A
C.3V,16A
D.3V,3A

The total voltage of three dry batteries is 4.5V, so the voltmeter with 0 ~ 3V range can not be selected. After a 10 ohm resistor is connected in series, the current in the circuit is 0.45a. If the range is too large, it is to protect the ammeter, but the reading will increase the error of the experiment, so a smaller range should be selected