Exercises of physical circuit diagram in grade three of junior high school

Exercises of physical circuit diagram in grade three of junior high school

(Wenzhou volume-31) Xiaoming's kitchen has an electric cooker, an induction cooker and a microwave oven. In order to compare the power consumption of these three appliances when heating water, he carried out the experiment with the help of his parents
（1） Measure 500ml of water, measure the initial temperature of the water, turn off other electrical appliances, connect the electric cooker to the circuit separately for water heating. When the turntable of the electric energy meter rotates for 100 turns, cut off the circuit immediately, and measure the final temperature of the water in the electric cooker. Then replace the electric cooker with induction cooker and microwave oven, and repeat the experiment. The results are shown in Table 1
（2） Increase the water quantity and the revolution of the electric energy meter, repeat the above experiment, and the results are shown in Table 2
(1) In addition to the watt hour meter, this experiment also needs the measurement tool is
(2) This experiment compares the power consumption of three kinds of electrical appliances through observation
(3) The preliminary conclusions of this experiment are as follows
5. (yiwujuan-32) in the scientific experiment, in order to measure the electric power of a small bulb with a rated voltage of 2.5 V, a student connected the circuit as shown in the figure
Experiment times
Voltage / volt
Current / A
(1) After closing the switch, he found that in the process of moving the slide of the sliding rheostat, the indication of the voltmeter and ammeter would not change, and the brightness of the bulb was always dark;
(2) After correcting the error, the student measured three sets of data (see the table above), then the rated power of the small bulb is watt;
(3) After the experiment, the student calculated the resistance of the light bulb according to the data in the table, and found that the resistance changed greatly

Physics problems in the third grade of junior high school
After the circuit is correctly connected, no matter how to adjust the sliding rheostat, the bulb will not light, and the voltmeter will show the number, and the current will always be zero. What is the cause of this failure?

The small bulb is short circuited, so there is no current passing through the bulb, and the voltmeter is open circuit, so it cannot pass through the current
That is to say, the voltmeter is directly connected to both sides of the sliding rheostat, so the voltmeter has indication

In the weather of thunder and lightning, in order to avoid the TV being struck by lightning, the following treatment methods are reasonable:
a. Turn off the TV
b. Turn off the TV and unplug it
c. Turn off the TV, unplug the power and ground the antenna
Please explain

b. Turn off the TV and unplug it
It must be right

A multiple choice question about electric current in Physics
When the positive and negative terminals of ammeter are connected reversely, the situation is ()
A. The pointer deflects to the right
B. The ammeter is burnt out
C. The pointer deflected to the side without scale and damaged the ammeter
D. The pointer must have been bent

C. The pointer deflected to the side without scale and damaged the ammeter