Xiaohong and Xiaowei have done the experiment of "measuring the electric power of small light bulb". There are two kinds of power supply (voltage is 6V), voltmeter, ammeter and sliding rheostat (a is marked with "50 Ω & nbsp; & nbsp; 2A", B is marked with "20 Ω & nbsp; & nbsp; It is known that the rated voltage of the two small lamps are 2.5 V and 3.5 V respectively, and the rated current is the same. They choose the equipment to carry out the experiment. Xiaohong connects the circuit correctly, connects a small lamp into the circuit, closes the key, moves the slide of the rheostat, and observes that the small lamp lights normally when the slide is near the midpoint. The ammeter shows the following As shown in the figure. ① during the experiment, the rheostat selected by Xiao Hong is______ (choose "a" or "B"), the rated voltage of the lamp she measured is______ V, rated current of______ Please calculate the rated power of Xiaohong and Xiaowei according to the relevant information______ (write the calculation process)

Xiaohong and Xiaowei have done the experiment of "measuring the electric power of small light bulb". There are two kinds of power supply (voltage is 6V), voltmeter, ammeter and sliding rheostat (a is marked with "50 Ω & nbsp; & nbsp; 2A", B is marked with "20 Ω & nbsp; & nbsp; It is known that the rated voltage of the two small lamps are 2.5 V and 3.5 V respectively, and the rated current is the same. They choose the equipment to carry out the experiment. Xiaohong connects the circuit correctly, connects a small lamp into the circuit, closes the key, moves the slide of the rheostat, and observes that the small lamp lights normally when the slide is near the midpoint. The ammeter shows the following As shown in the figure. ① during the experiment, the rheostat selected by Xiao Hong is______ (choose "a" or "B"), the rated voltage of the lamp she measured is______ V, rated current of______ Please calculate the rated power of Xiaohong and Xiaowei according to the relevant information______ (write the calculation process)

(1) The figure shows that the current representation is 0.26A or 1.3A. When the rated voltage of the bulb is 2.5V and 3.5V in series in 6V circuit, the partial voltage on the sliding rheostat is 6v-2.5v = 3.5V or 6v-3.5v = 2.5V respectively. Because the slide is near the midpoint of the rheostat, it is calculated according to the rheostat adjusted to 25 Ω and 10 Ω respectively

In power measurement, if the position of voltmeter and ammeter is changed, what will happen?

No indication of ammeter
The voltmeter works normally and is close to the supply voltage
Electrical appliances can't work properly

Use an ammeter to connect with the bulb in series. The current is 0.18a. Use a voltmeter to measure the voltage at both ends of the bulb is 220V. Try to calculate the resistance value when the filament is normally emitting

Resistance = 220 / 0.18 = 1222.2 ohm