Fill in the blanks

1. (Guilin 2005) In the circuit shown in the figure, the power supply voltage is 3V. After the switch is closed, the readings of ammeter and voltmeter are 0. 10A and 2.0V respectively, so the current through R2 is A, the voltage across R2 is V, and the resistance of R 1 is Ω.

2. (Tianjin 2005) In the circuit shown in Figure A, if the readings of voltmeter and ammeter are shown in Figure 8, the resistance of the small bulb is about Ω.

3. (Wuhu City, 2005) The resistance of a wire is 0.008 Ω. If it is accidentally connected directly to the poles of a dry battery, the short-circuit current is A. ..

4. (Shantou City, 2005) The expression of Ohm's Law is that the smaller the resistance R of a conductor, the greater the current I passing through the conductor under the condition of constant voltage U. Two resistors R 1 and R2 (R 1 > R2) are connected in series in the circuit, and the current passing through R 1 (fill in "greater than", "equal to" or "less than") passes through R2.

5. (Quanzhou 2005) As shown in the figure, the power supply voltage is 9V, the ammeter range is 0 ~ 0.6A, and the small bulb resistance is Ω. In order to prevent the current in the circuit from exceeding the range of the ammeter, the minimum resistance of the sliding rheostat connected to the circuit is ω.

6. (Yunfu City, 2005) A classmate designed an anemometer. As shown in the figure, O is the rotating shaft, OC is the metal rod, and the wind receiving plate is connected below. When there is no wind, OC is vertical, and the greater the wind, the greater the deflection angle of OC rod. AB is an arc resistance, and point P is the point where the metal bar contacts the arc resistance. A small light bulb is connected in the circuit. When measuring the wind, just turn off the switch S.

7. (Nantong 2005) In the circuit shown in the figure, close the switch S and move the slider P of the sliding rheostat. When the voltmeter indicates 6V, the current indicates 0.5A；; When the voltmeter indicates 7.2V and the current indicates 0.3A, the resistance R0 is _ _ _ Ω and the power supply voltage is _ _ _ _ V. 。

8. (Panzhihua City, 2005) The rated voltage of a small light bulb is 8V, and the current passing through it is 0.4A when it emits light normally. Now the light bulb is connected to the power supply of 12V, and it needs a _ _ _ _ _ _ _ Ω resistor to emit light normally.

9. (Xiangfan City, 2005) The bulbs L 1 and L2 are connected in series in the circuit. The total voltage across them is 12V, the resistance of L 1 is 8Ω, and the voltage across L2 is 4V, so the current in L 1 is _ _ _ a.

10. (Xiangfan City, 2005) As shown in the figure, it is known that the power supply voltage is 6V and the resistance R 1 is10Ω. After the switch is closed, the current is expressed as 1A, then R2 = _ _ _ _ ω, and the current through R2 is equal to _ _ _ _ _ A.

1 1. (Hechi City, 2005) The circuit is shown in the figure, with the resistance r1= R2 = 4Ω and the power supply voltage unchanged. When S 1 and S2 are closed, the indication of the ammeter is 0.75A at this time, and the circuit is _ _ _ _ _ _ _. When S 1 is closed and S2 is disconnected, the total resistance of the circuit is _ _ _ _ Ω, and the ammeter indicates _ _ _ _ _ A.

12. (Xicheng District, Beijing, 2005) When a voltage of 3V is applied across the conductor, the current passing through the conductor is 0.2A；; When a voltage of 6V is applied to this conductor, the resistance of this conductor is equal to _ _ _ _ _ _ _? .

13. (Gansu 2005) As shown in the figure, it is a schematic diagram of the rotating resistance box panel, and the resistance shown in the figure should be

Ω

14. (Harbin 2005) The school laboratory has an indicator light marked "10ω 1A" and a sliding rheostat marked "20ω 1A". A classmate connected them in parallel and connected them in the circuit. The normal working voltage of the indicator lamp is V, and the maximum allowable current on the main road is A. 。

14. (Huai 'an City, 2005) As shown in the figure, when the switch is closed and the slider moves to the position shown in the figure, the light bulb can just emit light normally. Now, when the slider of the sliding rheostat moves to the left, the pointer of the ammeter will _ _ _ _ _ _ _ (fill in "left bias", "right bias" or "static").

15. (Suqian 2005) As shown in the figure, the power supply voltage is constant, and the resistance r 1 = R2 = R3 = 10ω. Connect R2 and R3 in parallel, and close the switch. The ammeter indicates I1; Connect R 1 and R2 in series, switch S 1 and S2 should be (filled with "ON" or "OFF"), and the ammeter indicates I2; Then i 1: I2 =.

16. (Nanjing 2005) Circuit diagram, constant power supply voltage, resistance r 1 = 5ω, R2 = 15ω.

(1) If both switches Sl and S2 are turned off, the current representation number is O.2A, and the power supply voltage is V;

(2) If both switches S 1 and S2 are closed, the current is expressed as O.9A, and the current through resistor R3 is a. 。

17. (Wuxi 2005) Xiaoming designed a pressure measuring instrument as shown in the figure, which can reflect the pressure on the metal plate above the spring. Where r' is a sliding rheostat, r is a constant value resistor, the power supply voltage is constant, and the pressure gauge is actually a voltmeter. When the pressure on the metal plate increases, the resistance value and pressure representation of the rheostat (optional "increase", "decrease" or "constant").

18. (Wuxi 2005) At a certain temperature, the relationship between the current in two circuit elements A and B and the voltage at both ends is shown in the figure. As can be seen from the figure, the resistance of element A is ω; If A and B are connected in parallel across a power supply with a voltage of 2. OV, the total current through a and b is a. ..

19. (Chongqing 2005) When the voltage across the conductor is 4V, the current passing through it is 0.5A, and the resistance of the conductor is ω; When no voltage is applied to this conductor, the resistance of this conductor is ω.

20. (Chongqing 2005) Bell, resistance10Ω, rated voltage 6V. At present, there is only one power supply with 9V voltage. In order to make the bell work normally, a resistor with a resistance of Ω should be connected (series or parallel connection is optional).

2 1. (Gansu, 2005) In the circuit shown in the figure, the power supply voltage is U = 10V. When the switch S is closed, the voltage between ac is 5V, and the voltage between B and D is 7V. If the resistance r1= 4Ω is known, the resistance of the resistor with the largest resistance among the three resistors is. .

Second, multiple choice questions

1. (Beijing, 2005) As shown in the figure, the voltage across the power supply is constant, the switch s 1 is closed, and s2 is turned off. If the readings of voltmeter and ammeter increase, the following operations must be feasible ().

A. slide the slider p of the sliding rheostat to the right.

B. the slider p of the sliding rheostat moves to the left.

C. slide the slider p of the rheostat and turn off the switch S2.

D slide the slider p of the sliding rheostat and turn off the switch S 1.

2. (Yunfu City, 2005) As shown in the figure, the power supply voltage is constant. When S is closed and the slider of the sliding rheostat moves to the right, the following statement is correct ().

A. The light bulb lights up and the voltmeter reading remains unchanged. B. The light bulb darkens and the voltmeter reading becomes smaller.

C. the light bulb becomes brighter and the voltmeter reading becomes larger. D. the light bulb becomes brighter and the voltmeter reading becomes smaller.

3. (Beihai City, Liuzhou City, 2005) In the experiment of measuring the resistance of small light bulbs, Xiaoming designed three circuit diagrams shown in Figure L, and the correct one is ().

A.A，C，B，C，A，B，D，A，B，C。

4. (Hebei Province in 2005) In the circuit shown in the figure, the power supply voltage is constant. When the switch S is closed and the slider P of the sliding rheostat moves to the right, the following judgment is correct ().

A. the current means bigger, and the voltage means smaller.

B. Current means smaller, while voltage means constant.

C. the current means smaller, and the voltage means larger.

D. The current means bigger, while the voltage means constant.

5. (Hebei Province in 2005) As shown in the figure, the power supply voltage remains unchanged. When the switch S 1 is turned on and S2 is turned off, the ammeter indicates 0.2A；; When switches S 1 and S2 are closed, the indicator of ammeter is 0.8A, and the ratio of resistance R 1 to R2 is ().

a、 1:3 B、3: 1 C、2:3 D、3:2

6. (Jiaxing City, 2005) As shown in the figure, the resistance of lamp L 1 is R 1, and the resistance of lamp L2 is R2, r 1 > R2. Close the switch, and the current of lines A, B and C is ().

The current in A.a is the largest, and that in B.b is the largest.

Direct current is as big as direct current.

7. (Lujiang County, 2005) Connect two resistance wires A and B to the same voltage, and the current in wire A is greater than that in wire B, ignoring the influence of temperature. The following judgment is wrong ().

A. When their materials and thicknesses are the same, the length of line A is longer than that of line B. When their materials and lengths are the same, the thickness of line A is thicker than that of line B..

C. When their length and thickness are the same, the materials of the two wires must be different. D the materials, lengths and thicknesses of the two resistance wires a and b cannot be exactly the same.

8. (Panzhihua City, 2005) As shown in the figure, the power supply voltage is unchanged, and the lamp L can emit light after the switch S is closed. When the slider p slides to the right, the following judgment is wrong ().

A. when the light l is on, the indicator of voltmeter v becomes larger. B the indication of ammeter A 1 becomes larger, and the indication of A2 becomes smaller.

C. the electric power consumed by the resistor R0 is reduced. The lamp l goes dark and the voltmeter v goes down.

9. (Suzhou, 2005) As shown in the figure, AB and BC are two conductors made of the same material with the same length and different cross-sectional areas, which are connected in series to access the circuit. Comparing the voltage across the two conductors with the current through them, there is ().

A.UAB & gt； UBC，IAB & ltIBC·UAB & lt； UBC，IAB=IBC

C.UAB & gt； UBC，IAB = IBC D UAB = UBC，IAB & ltIBC

10. (Taizhou, 2005) As shown in the figure, the battery voltage is constant. About the working state of the circuit, the following statement is correct ().

A. when only S 1 is turned off, two bulbs are connected in series.

B if S 1 is turned off first, and then S2 is turned off, the readings of voltmeter and ammeter will become smaller.

C if S 1 is turned off first, then S2 is turned off, the readings of voltmeter and ammeter will become larger.

D if S 1 is turned off first, and then S2 is turned off, the voltmeter reading remains unchanged and the ammeter reading becomes larger.

1 1. (Wuhan, 2005) As shown in Figure (a), when the switch S is closed, the readings of two ammeters are read out from Figures (b) and (c) respectively, then the current in the lamp L 1 is ().

a、0.8A B、0. 16A C、0.52A D、 1.28A

12. (Wuhan, 2005) In the figure, R 1 is a constant resistor and R2 is a sliding rheostat, so the following statement is correct ().

When (1)R2 is constant, the ratio of V 1 reading to A reading is equal to R 1 (2)R2 is constant, the ratio of V2 reading to A reading is equal to R 1 (3)R2 changes by a certain amount, and the absolute value of the ratio of V2 reading to A reading is equal to R1(.

a 、( 1)3)4)B 、( 2)3)4)C 、( 2)3)D 、( 2)4)

13. (Hechi City, 2005) 24. As shown in figure 12, when the switch s in the A circuit is closed,

When the pointer positions of the two voltmeters are shown in Figure B, the voltages across the resistors R 1 and R2 are () respectively.

a、 1.2V、6V

c、4.8V、 1.2V D、 1.2V、4.8V

The circuit in 14. (Bijie, 2005) is shown in the figure; Keep the power supply voltage and bulb resistance unchanged, close the switch S, move the slider P of the sliding rheostat to the right, and then ().

A. current means increase and voltage means decrease. B. Current means decrease and voltage means increase.

C. current means increase, and voltage means increase. D. current means decrease, and voltage means decrease.

15. (Harbin, 2005) As shown in the figure, when the sliding blade of the sliding rheostat moves between two points, the reading range of the ammeter is between 1A and 2A, and the reading range of the voltmeter is between 6V and 9V. Then the resistance value and power supply voltage of the constant resistor R are .........................................

a . 3ω 15V b . 6ω 15V

c . 3ω 12V d . 6ω 12V

16. (Henan Province, 2005) The small light bulb in the circuit shown in Figure 6 emits light normally. If the position of the light bulb and ammeter is reversed, then ().

A. the light bulb doesn't work. Small light bulbs will burn out

C. the current representation remains unchanged. The voltage representation remains unchanged.

17.(2005 Heilongjiang) In the following circuit diagram, the same components have the same specifications. When the switch is closed, the sliding rheostat can be used to change the lamp.

The brightness of the bubble, and will not cause circuit accidents is ()

18. (Jinan, 2005) In the circuit shown in the figure, the power supply voltage is constant. Close the switch S and adjust the sliding rheostat to make the small bulb L emit light normally; If the switch S is turned off again, slide the slider () of the rheostat to make the bulb L still glow normally.

A. Move to the finish line. A.B. Move to the finish line. B.C. Stay still. D. unable to judge

19. (Suqian, 2005) Connect the resistors R1= 3Ω and R2 = 6ω into the same circuit. About their total resistance (equivalent resistance), among the following four options, it is impossible to ().

A.9 ω b.2 ω c.9 ω or 2 ω d.3 ω.

20. (Suqian City, 2005) As shown in the figure, among the following four equations, the one that conforms to the characteristics of parallel circuits is: ()

A.I = I 1+I2

B.U = U 1+U2

C.R = R 1+R2

D.

2 1. (Jinhua, 2005) In household circuits, measuring pens are often used to distinguish between live and neutral wires. The voltage of the household circuit is 220 volts. As shown in the figure, when students touch the fire line with a measuring pen with 800 kiloohms resistance, the neon tube glows. The human body resistance between the classmate's hand and the ground is 80 kiloohms, so the current passing through the classmate is ().

A.0.275 mA B.2.75 mA

C.0.25

22. (Jinhua City, 2005) In the circuit shown in the figure, the power supply voltage is always 24 volts, the resistance r 1 = R2 = 120 ohms, and the range of both ammeters is 0-0.6 amps. When the switch is closed, both ammeters read 0.2 ampere. If the fault is caused by one of these two resistors, the fault is ()

A.R2 short circuit B.R2 open circuit

C.R 1 short circuit D.R 1 open circuit.

23. (Lianyungang, 2005) After learning the knowledge of electricity, the physics interest group explored the emergency lamp with adjustable brightness, and found that its brightness level switch is equivalent to a sliding rheostat, and the circuit is shown in the figure. Close the switch, measure with voltmeter and ammeter, and adjust the sliding rheostat to brighten the bulb. During this process, the indication of voltmeter and ammeter changes to (power supply voltage remains unchanged).

A. the indicator of ammeter a becomes smaller. B. the indication of voltmeter V 1 becomes larger.

C. the indication of voltmeter V 1 becomes smaller. The indication of V2 voltmeter remains unchanged.

24. (Nanjing, 2005) In the circuit shown in Figure 4, the power supply voltage remains unchanged. After closing the switch s, when sliding,

When the slider P of the rheostat moves to the left, the following judgment is correct ()

A. the current means bigger, and the voltage means smaller. B. Current means bigger, and voltage means bigger.

C. the current means smaller, and the voltage means larger. D. Current means smaller, and voltage means smaller.

25. (Nanjing, 2005) has two constant resistors R 1 and R2 with different resistances, and their current-voltage relationship diagram is shown in Figure 7. If R 1 and R2 are connected in series, the total resistance is R series, and the total resistance is R parallel, the following statement about the area where the I-U diagram of R series and R parallel is located is correct.

A. r string in region II, r in region III. B. r string in region III, r in region i.

C.r string in region I, R in region II D.R string in region I, R in region III.

26. (Shaoxing City, 2005) In the circuit shown in the figure, when the switch S is closed and the slider P of the sliding rheostat moves to the right, the changes of the voltmeter and the current indicator are ().

A. the readings of voltmeter and ammeter have increased. The readings of voltmeter and ammeter have dropped.

C. Voltage means bigger, and current means smaller. D. voltage means smaller, and current means larger.

27. (Wuxi, 2005) As shown in the figure, the power supply voltage is constant, and the lamp L can emit light after the switch is closed. When the slider p slides to the left, the following judgment is correct ().

A. voltage means smaller, and current means larger. B. Voltage means bigger, and current means smaller.

C. Voltage means bigger, and current means bigger. D. voltage means smaller, and current means smaller.

28. (Xuzhou City, 2005) As shown in the figure, when the slider of the sliding rheostat slides to the N end, the change of ammeter and voltage representation is ().

A. both representations become larger. Both representations are smaller.

C. the current indicator becomes larger and the voltage indicator becomes smaller. D. The current indicator becomes smaller and the voltage indicator becomes larger.

29. (Yancheng, 2005) Xiao Gang used the circuit shown in the figure to discuss the relationship between current and resistance in the circuit. In this experiment, when the resistance between A and B changes from 5 Ω to10 Ω, the only operation he should take to explore the above problems is ().

A. keep the rheostat slider still. Move the rheostat slider to the left appropriately.

C. move the rheostat slider to the right appropriately. D. increase the number of batteries.

30. (Zhenjiang City, 2005) As shown in the figure, the resistance r1= 3Ω, R2 = 6ω, and the indicator of ammeter A is 0.6A, then the indicator of ammeter A 1 is ().

A.0.6A B.0.4A C.0.2A D.0. 1A

3 1. (Zhenjiang, 2005) In the figure, 1 and 2 are the curves of the relationship between current and voltage obtained by measuring two constant resistors R 1 and R2 with different resistance values by voltammetry, so the relationship between their resistance values is ().

a . r 1 > r2b . r 1 < r2c . r 1 = r2d。 Can't judge.

32. (Chongqing, 2005), as shown in the figure, is a device for automatically measuring the oil level in the fuel tank. R is a sliding rheostat, and its metal slider is one end of the lever, because the positioning baffle can only slide on the resistor. The height h of the oil level in the oil tank can be known from the scale pointed by the pointer of the oil meter (modified from the ammeter). Known current increases, ammeter pointer deflection to the right, then ()

A, when the oil level drops, ammeter pointer deflects to the right. B, the zero scale line of the oil meter must coincide with the original zero scale line of the ammeter.

C, the scale value of the oil meter increases gradually from left to right. D, the less oil in the tank, the greater the current flowing through the ammeter.

33.(2005 Haidian Volume) Figure 8 is an experimental circuit for Xiao Li to explore circuit changes, where R 1, R2 is a fixed resistor and R0 is a sliding rheostat.

Rmax is the maximum resistance of sliding rheostat, and the voltage at both poles of power supply is constant. R1> is known; R2 & gt； Rmax, when sliding

34. (Changsha, 2005) Scientific methods such as "controlled variable method", "equivalent method" and "analogy method" are often used in physics research. In the following research example, the control variable method is ().

A. When studying the causes of current formation, compare current with water flow, and analyze the formation of current by analyzing the formation of water flow.

B. When studying the current, judge the current according to the effect produced by the current.

C. When studying a circuit composed of multiple resistors, find the total resistance of the circuit, and replace the total effect produced by all resistors with the effect produced by the total resistance.

D. When studying the relationship between current and voltage, keep the resistance constant, change the voltage across the resistance, and observe how the current changes with the voltage.

35. (Gansu in 2005) A and B conductors are connected in parallel, and the ratio of current passing through them is 2: 1, and the ratio of resistance of A and B conductors is ().

a . 2: 1 b . 1: 1 c . 1:2d . 1:3

Third, experiments and inquiry questions

1. (Huanggang, 2005) When Xiaogang measures the resistance of a small 2.5V bulb, the connected circuit is shown in the following figure:

The number of experiments is12 3.

Voltage U/V 2.0 2.5 2.8

Current I/A 0.20 0.24 0.25

(1) Check the circuit and find that there is a wrong wire connection. Please put an "x" on the wrong connection line. If no mistakes are found, turn on the switch and something will happen. Draw the correct connection in the picture. Before closing the switch, he should adjust the sliding blade of the sliding rheostat to the end (fill in "A" or "B").

(2) After Xiao Gang corrected his mistakes, the data measured according to the correct operation are shown in the right table:

The resistance of the small bulb measured at 1 time is: As can be seen from the table, the resistances of the three small bulbs are not equal. What do you think is the possible reason?

2. (Linyi City, 2005) Sun Nan used the circuit shown in the figure to study the relationship between the current in the conductor and the conductor resistance. He successively connected the fixed-value resistors of 5Ω,15Ω and 25Ω to the two points of the circuit A and B, closed the switch S, and read out the current (as shown in the following table). It can be seen from the experimental data that the current I is not inversely proportional to the resistance R.

Q: (1) What equipment is wrong with this experiment? Please name the equipment that should be replaced.

(2) What instruments are needed to ensure the correct experiment?

3. (Qingdao, 2005) The team measured the resistance of small bulbs, and the designed circuit diagram has an error of 1. Please circle the mistakes and correct them on the original picture. Then according to the revised circuit diagram, connect the unfinished physical diagram.

Using the modified experimental circuit, Pony got the following data:

The picture shows the dial of voltmeter in the first experiment. The above table is incomplete in two places. Please fill in completely: At this time, the electric power of the small light bulb is

w .

4. (Qingdao, 2005) Ma Xiao has a circuit box with a red light and a green light on the panel (as shown below), two switches S 1 and S2, and a voltmeter. Without opening the box, he asked other students in the group to explore the circuit structure in the box. To this end, Xiao Zhang did the following experiments:

According to the experiment, please draw the circuit diagram of the circuit in the box:

5. (Wuhu City, 2005) When conducting experimental research on the influence of conductor material, length and cross-sectional area on resistance, the available conductor specifications are as follows:

Material number length /m cross-sectional area /mm2 Material number length /m cross-sectional area /mm2

Nickel-chromium alloy ① 1.5 Mn-Cu ⑤ 1.5.

② 1 1 ⑥ 1 1

③ 1.5 0.5 ⑦ 1.5 0.5

④ 1.5 1 ⑧ 1.5 1

What do you think is the most reasonable group for the conductor to choose ()

Answer. ③ ④ ⑤ ⑥ B、② ③ ⑥ ⑦ C、① ⑤ ⑥ ⑦ D、⑤ ⑥ ⑦ ⑧

6. (Shantou City, 2005) Read the following passage:

Conductors conduct electricity easily, but insulators do not. There are some materials whose conductivity is between conductor and insulator. This material is called semiconductor. In addition to conductivity, semiconductors have many special electrical properties, which make them have many important applications.

The resistance of some semiconductors drops rapidly after being heated; Conversely, with the decrease of temperature, the resistance increases rapidly. This kind of semiconductor can be used to make small-size thermistors. Thermistor can be used to measure the temperature change in a small range with fast response and high accuracy.

Answer the following questions:

(1) If the thermistor, power supply, ammeter and other elements are connected in series to form a circuit, other factors remain unchanged, as long as the temperature in the area where the thermistor is located decreases, the current in the circuit will change (fill in "big" or "small").

(2) In the above circuit, we can replace the current scale in the ammeter with the corresponding temperature scale to directly display the temperature near the thermistor. If the temperature scale in the center of the dial is 20℃ (as shown in figure 15), the scale of 25℃ should be on the side of 20℃ (fill in "left" or "right").

(3) In order to put the thermistor in the vegetable greenhouse to detect the temperature change in the greenhouse, please design a circuit with the equipment (additional components) in Figure 16.

7. (Guilin, 2005) The method of "controlling variables" was adopted in the experiment to explore the factors related to conductor resistance. The following table is a record of the related physical quantities of the conductors used by the experimental group in the experiment:

(l) To explore whether the conductor resistance is related to the length, two conductors should be selected;

(2) To explore whether the conductor resistance is related to the cross-sectional area, two conductors should be selected.

8. (Yichang City, 2005) As shown in the figure, it is an experimental device for measuring resistance with voltmeter and ammeter.

(1) Connect the physical diagram B completely according to the circuit diagram shown in Figure A, and require the ammeter and voltmeter to be connected with low range.

(2) Figure C is the data of voltmeter during a certain measurement, so the reading of voltmeter at this time is, if the reading of ammeter at this time is 0. 16A, the resistance is Ω.

Methyl ethylene propylene

9. (Nantong, 2005) There is a resistor Rx, and its resistance value is not clear, so it needs to be measured.

(1) Xiaoming connects the circuit according to the circuit diagram of Figure 18, and turns off the switch S after checking that it is correct. It is observed that the voltmeter indicates 1.6V, and the ammeter indicates as shown in the figure, so the current flowing through the resistor Rx is _ _ _ _ A, and the resistance of Rx is _ _ _ Ω.

In the experiment, in order to reduce the error, Xiao Ming also needs to do the following.

_______________________________________________________________。

Fig. 20 is a physical picture of the tiger connection in this experiment. Please point out three mistakes or shortcomings.

①_____________________________________________________

②_____________________________________________________

③_____________________________________________________

10. (Lujiang County, 2005) The conductor is represented by a stroke line and connected to the circuit in Figure 5A. Requirements: the light bulb L 1 is connected in parallel with L2; Measure the current in L 1 with an ammeter. When the switch is closed, the ammeter pointer is shown in Figure B, and the current through L 1 is A. ..

1 1. (Lujiang County, 2005) When discussing the relationship between current and voltage on a resistor:

(1) What questions will we ask first? ;

(2) Do you or your classmates have any guess? Please say it:

(3) When designing the experiment, the voltage needs to be changed. What methods did you and your classmates use in the experiment? (Name the equipment and methods used);

(4) By analyzing the recorded data, you come to a conclusion.

12. (Suzhou, 2005) Xiaoming did an electrical experiment. By changing the resistance of sliding rheostat R3, the readings of voltmeter and ammeter recorded in turn are shown in the following table.

Analyze the experimental data in the table. It can be inferred that the circuit used in Xiaoming's experiment may be one of the following circuit diagrams ().

13. (Suzhou, 2005) We know that there is always an error in measurement, and the difference between the measured value and the true value is usually called absolute error. The accuracy level of ammeter used in junior middle school electrical experiment is generally 2.5. The significance of class 2.5 ammeter is that the maximum absolute error when measured with this ammeter does not exceed 2.5% of the full-scale value. The following table shows the ammeter when measuring current with a 2.5-level ammeter.

(1) The percentage error corresponding to the last space in the above table should be _ _ _ _ _ _ _%.

(2) As can be seen from the data in the above table, the greater the deflection angle of the ammeter pointer, the _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

(3) If the percentage error is less than 3.75% when measuring with an ammeter with a precision of 2.5, the deflection angle of the ammeter pointer should be greater than _ _ _ _ _ of the full scale.

14. (Taizhou, 2005) Do the experiment of measuring the resistance value of the resistor.

(1) Xiaoming connects the experimental equipment in Figure 2 1 into an experimental circuit according to the circuit diagram shown in Figure 20. Liang Xiao of the same group thinks that there is a wiring error in the experimental circuit from the experimental purpose, and suggests Xiaoming to change it. Please put an "X" on the wrong wire; ② Pull another wire to make the circuit connected correctly; (3) If this line is not connected, the impact on the experiment will be _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.

Explain what the impact is.

(2) After Xiao Ming reconnects the circuit correctly, close the switch and adjust the slider of the rheostat to a certain position. When the voltmeter and ammeter indicate as shown in Figure 22, the voltmeter reads V, the ammeter reads A, and the resistance of the measured resistor Rx is Ω.

(3) Xiao Ming and Xiao Liang are glad that they got the measurement results first in their class, and they will finish the experiment by arranging the experimental equipment. Do you think their experiment is really over? What advice would you give them? Write down your suggestion:

__________________________________________________________________________;

② The purpose of your proposal is: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.

14. (Wuhan, 2005) In the circuit shown in the figure, all the equipment is intact except one wire is broken. The power supplies of RL1=10Ω and RL2 = 5Ω consist of two new batteries. In order to find this lead, Xiaogang adopted the following methods: connect the positive terminal of the electric meter with the positive terminal A of the power supply, and then connect the negative terminal of the electric meter with the terminal B of L 1 and the terminal C of L2 respectively, and judge this lead by observing the instructions of the electric meter.

(1) Which of the following rice should Xiaogang choose before the above operation? Voltmeter with a measuring range of 3V; Voltmeter with range of 15V; C ammeter with a range of 0.6A

(2) After selecting the correct ammeter, when the ammeter is connected to point A and point B, if the ammeter has instructions, it must be disconnected; If the meter doesn't show numbers, the wire may be broken. When the ammeter is connected to point A and point C, if the ammeter has instructions, the conductor is not broken. At this point, the ammeter indicates.

15. (Guigang, 2005) gives the following equipment: a power supply with a voltage of 3V; B. a voltmeter with a measuring range of 3V; C. voltmeter with range of 15V; D. ammeter with measuring range of 0.6A; E. ammeter with a measuring range of 3A; Sliding rheostat; Switches and wires.

Now it is necessary to measure the resistance of a resistor RX, which is about10Ω.

(1) In order to improve the accuracy of the experiment, equipment A, F, G and (fill in the equipment code) should be selected.

(2) Figure 13 is the physical connection diagram during the experiment, in which the sliding rheostat has not been connected. Please indicate the wires connecting it to the circuit with a stroke line.

(3) When the switch is closed to connect the circuit and the slider of the sliding rheostat moves, it is found that the readings of the ammeter and voltmeter are relatively small and do not change with the movement of the slider. The possible reason is that the two terminals of the sliding rheostat are connected to the circuit.