(09 Jiangsu). As shown in the figure, when the wire is connected between circuits A and B, the wire is connected to the light bulb. If different conductors are connected between A and B respectively, the switch is closed, and the resistance of different conductors can be judged by observation and comparison. If the resistance of the two conductors is not much different, an ammeter can be used instead of a light bulb for further judgment.
Answer: string bulb brightness current
(09 Chengdu) In the experiment of "Exploring what factors are related to the resistance of conductors".
(1) Xiaoming's guess is: ① the resistance may be related to the material of the conductor;
Xiao Liang's guess is: ② The resistance may be related to the temperature of the conductor;
Xiao Min's guess is: ③ The resistance may be related to the length of the conductor;
According to your electrical knowledge, you think: ④ Resistance is also related.
(2) Figure 15 shows three students doing the above research.
They have completed some prepared experimental equipment.
Physical connection.
If the resistance is negligible due to temperature, explore it.
Guess (1) should be controlled; To explore conjecture ③, choose conductor _ _ _ _, conductor _ _ (fill in the blanks.
Conductor code letters).
Answer:
(09 Chengdu). In the following objects, semiconductor materials are used.
A. intelligent robot dog B. incandescent light bulb C. ordinary dry battery D. sliding rheostat
A: A.
(09 Ningbo) 20. When studying the relationship between current and resistance at a certain voltage, the circuit is shown in the figure. The power supply voltage is constant at 3V, and the words "15Ω1a" are marked on the sliding rheostat. Connect fixed-value resistance rulers with different resistances between A and B in turn, move the slider P to make the voltage expressed as 1.5V, and read the instructions of the ammeter. When a 20 Ω resistor is connected between A and B, the voltage indicates that it will never reach 1.5V, which may be due to ().
A. the resistance of sliding rheostat is too small. B. 3V power supply voltage is too high.
The resistance of C.C.20Ω is too small. D. 1.5V control voltage is too high.
A: A.
(09 Jinhua) 34. When Xiao Ming explored "the relationship between current and voltage passing through conductors", the circuit diagram and physical diagram were as shown in the figure. It is known that the power supply voltage and the resistance value of resistor R 1 are constant, the measuring range of ammeter A is 0 ~ 0.6 A, voltmeter V 1 is 0 ~ 3 V, voltage Qiuv2 is 0 ~ 15 V, and the words "50Ω1a" are marked on the sliding rheostat R2.
(1) Xiaoming connects objects according to the circuit diagram. Before closing the switch, the slider of the sliding rheostat should be placed at the ▲ end (fill in "left" or "right"). When the switch is closed, it is found that the readings of ammeter A and voltmeter V 1 are zero, and the readings of voltmeter V2 are not zero. If the resistor R/Kloc-0 and/or the sliding rheostat R2 in the circuit fails, the fault is ▲.
(2) After troubleshooting, continue the experiment and record the readings of ammeter A and voltmeter V 1 to obtain a set of experimental data, as shown in the following table.
By analyzing the experimental data in the table, it can be concluded that the current passing through the conductor is proportional to the voltage when the resistance of the conductor is constant.
(3) In the experiment, record the readings of ammeter A and voltmeter V2 to obtain a set of experimental data, and make a U-I diagram (solid line) according to the experimental data, as shown in the figure. Under the premise of ensuring the safety of experimental equipment, the maximum current allowed to pass in the circuit is ▲ A.
Answer: (1) Right sliding rheostat R2 is on (2) plus (3)0.3.
(09 Pingyuan County, Shandong Province) The safe voltage of human body is not higher than 36V. When the current passing through human body is close to 30 mA, it will be life-threatening. It can be inferred that the human body is (filled with "conductor" or "insulator") and its resistance is about Ω.
(09 Jiangsu) 22. The rated voltage of the lighting lamp is 36V, and the filament resistance is 24Ω when it emits light normally, so the rated current of the lighting lamp is A. If the power supply voltage is 48V, a resistor with a resistance of Ω can be connected in series to make the lighting lamp emit light normally.
Answer: 1.5 8
Yantai (09) 25. In the experiment of measuring conductor resistance by voltammetry.
(1) The physical circuit connected by Xiaoming is shown in figure 18. There are some mistakes, please put an "X" in the mistakes and correct them.
(2) The following table is the experimental report prepared by Xiao Ming. Please fill in the three blanks in the above report.
Experimental name "Voltammetry to measure resistance"
Experimental purpose to measure the resistance of unknown resistor R.
Experimental principle
Ohm's Law
Experimental circuit diagram
Experimental step ① Connect the circuit according to the circuit diagram, and adjust the slider P of the sliding rheostat to _ _ _ _ _ _ _ _ _ _ _, so as to maximize the resistance of the connected circuit.
② Turn off the switch, adjust the slider P, and read the readings of voltmeter and ammeter.
(3) According to the measured voltage value and current value, find the resistance value of R. ..
The voltage U/V, current I/A and resistance R/ω were recorded experimentally.
2.0 0.20
A brief conclusion of the experiment
(3) From the "experimental steps", what are the main defects?
Answer:
(1) See Figure 3. (voltmeter and ammeter are connected correctly, each 1 min) (2) See Figure 4 for the circuit diagram. (1 min) l0( 1 min) is at the B end or the right end.
(3) Not measured many times. (2 points)
(09 Guangzhou) 23. Measure the resistance value of resistor r with the instrument shown in fig. 20.
(1) Connect the circuit of Figure 20 to the correct measuring circuit.
(2) The sliding rheostat protection circuit in the circuit. Therefore, before the switch is closed, its slider should be moved to the _ _ _ _ _ end (fill in "left" or "right"); In the process of experiment, sliding rheostat and _ _ _ _ _
(3) If the readings of ammeter and voltmeter in the circuit are as shown in Figure 2 1, the readings of ammeter and voltmeter are _ _ _ _ _ _ _ _ _.
Answer: (1) As shown in Figure (2), change the voltage and current at both ends of the resistor to the left, so as to measure the average value many times and reduce the error.
(3) 0.4 A 2.4 V
(09 Fuzhou) 23. (4 points) In the circuit of Figure 14, r1=10Ω, R2 = 20ω. After the switch is closed, the ammeter indicates 0.3A.
What is the voltage across the (1) resistor R 1? (2) What is the current flowing through R2?
Answer: Solution: (1) The result is u1= i1r1= 0.3a×10ω = 3v.
(2)∵R 1, R2 in parallel ∴U2 = U 1= 3V.
= 3v 20ω= 0. 15A
A: Omit.
(09 Chengdu) Repairing electrical appliances requires a 4 Ω resistor, and the repairman has four resistors at hand, their codes and resistance values.
The values are r 1 = 1ω, R2 = 3ω, R3 = 6ω, R4 = 12ω respectively.
(1) Please design a scheme, only two of the resistors are selected, and the "equivalent" resistor with a resistance of 4Ω is obtained by connecting the resistors in series or in parallel.
(It is required to draw the connection diagram of the resistor in the dotted box on the right, and mark the code name of the resistor without any explanation. )
(2) If the obtained "equivalent" resistor with a resistance of 4Ω is connected to both ends of a power supply with a voltage of 6V, find the electric power consumed by the smaller of the two resistors you choose.
Answer:
(09 Hangzhou) 37. The circuit shown in figure 1 is a schematic diagram of an automatic thermostat, which works at an ambient temperature of about 10c. The resistance in the box Rl = 5kΩ, R2 is a thermistor, and the graph of its resistance changing with temperature is shown in Figure 2, and the power supply voltage is 12V. When the voltage Uab between the two access points A and B of the voltage discriminator is less than 2V, the discriminator will turn on the switch S, so that the heating wire in the constant temperature box will be electrified and heated, thus raising the temperature in the box. When Uab is greater than 4V, the discriminator will turn off S and stop heating.
(1), as can be seen from Figure 2, when the ambient temperature is 150C, the thermistor R2 is kω.
(2) In what range will the temperature in the incubator be kept by calculation?
(3) What measures can be taken to reduce the temperature variation range in this incubator on the basis of the second question under the condition that the function of frequency discriminator and thermistor remain unchanged?
(09 Wenzhou) 37. Xiao Ming wants to explore the relationship between the resistance value R of a resistor and the temperature T, and designs the circuit shown in the figure below, in which the fixed resistance RO = 20 ohms and the power supply voltage U = 3 volts. He put the resistor at different temperatures to do experiments and got the resistance value of the resistor at different temperatures (as shown in the table below).
(1) According to the data in the table, the mathematical relationship between resistance value Rt and temperature T is ▲.
(2) Through calculation, how many volts did Xiao Ming observe in the experiment when the temperature was 0℃? ?
(3) During the experiment, Xiao Ming found that when the temperature is high, with the increase of temperature, the voltage expression number has no obvious change. After inspection, the circuit connection is normal and the components are not damaged. What do you think led to Xiaoming's discovery? ▲ 。
(09 Yantai) 27. After learning the related knowledge of electricity, the school held a comprehensive practical activity, the theme of which was to make a simple electronic scale with ammeter or voltmeter. Fig. 20 is a schematic diagram of an electronic scale designed by Xiaohong, where E is a dry battery (2 sections); A is ammeter (digital dial of electronic scale); R0 is a constant resistance (5 Ω); R is a uniform resistance wire with a length of 6cm, and the resistance value is15 Ω. C is the spring, and the relationship between pressure F and compression △L is shown in Figure 2 1 (g is 10N/kg, ignoring the gravity of the plastic disc. When making, adjust the length of the spring so that the slider P is just at the A end of the resistance wire when it is not weighed.
(1) What is the maximum weight of this electronic scale? What is the maximum range of ammeter that can be selected?
⑵ When the ammeter pointer is in O. 3A, what is the weight?
(3) Explain the biggest deficiency of the scheme in theory and draw your design schematic diagram.
Answer:
(09 Huzhou) 37. Zhang Lin designed an anemometer, and Figure A is its schematic diagram. Fixed resistance RO = 10Ohm, Rl is a pressure sensor (its resistance value will change with pressure, and the relationship is shown in Figure B), the power supply voltage is constant at 3 volts, the ammeter range is 0-0.6 A, and the air pressure plate is a rectangular light plastic plate with an area of 0.4 m2.
(1) The purpose of connecting R0 in the circuit is
(2) After closing the switch, the ammeter reads 0. 15A. What is the pressure on the wind pressure plate?
What is the wind speed at this time?
(3) What do you think of the shortcomings of this anemometer (just write a little).
Answer:
(09 Taian) 2 1. There is a storage battery in the laboratory, the voltage label is fuzzy, and the voltage is about 20V. At present, the laboratory has the following equipment: 1 constant resistance R0 (resistance value is 1 0Ω), 1 sliding rheostat (resistance value ranges from 0 to 20Ω) and1standard resistance box (resistance value ranges from 0 to 999Ω, circuit symbol is ""), with a range of.
Please choose the appropriate equipment to form an experimental circuit to measure the voltage value of the battery.
(1) Draw the experimental circuit diagram you designed in the box.
(2) Briefly describe the measurement steps after connecting the circuit (the measured physical quantities are represented by physical symbols):
(3) Write the expression of battery voltage u (expressed by measured physical quantity and known quantity), where u =.
Answer:
Option 1:
(1) circuit diagram as shown in the figure (3 points)
(2)① Move the sliding blade of the sliding rheostat to the maximum resistance;
② Turn on the switch and read the indicator U 1 of the voltmeter. (2 points)
(3) R0+RRR0U 1 (or 3U 1)(2 points)
Option 2:
(1) circuit diagram as shown in the figure (3 points)
(2)① Move the sliding blade of the sliding rheostat to the maximum resistance; ② Turn on the switch and read the indicator U 1 of the voltmeter. (2 points)
(3) r0+rxrx u 1 (or 32 U 1) (2 points)
Option 3:
(1) circuit diagram as shown in the figure (3 points)
(2)① Adjust the resistance box to the maximum resistance of the resistance; (2) close the switch, adjust the resistance box to a reasonable resistance value (the specific resistance value is reasonable, with points), and read out the voltmeter indicating U 1. (2 points)
(3) R0+RRR0U 1 (or specific multiple relation) (1 fraction)
Note: Other schemes are correct and the scores are equal.
(09 Pingyuan County, Shandong Province) As shown in the figure, the power supply voltage is constant. When the key k is turned off,
A. Voltage means smaller, current means smaller, and the lamp is dimmed.
B. The voltage indicator becomes larger, the current indicator becomes larger, and the light becomes brighter.
C. The voltage representation is constant, the current representation is constant, and the brightness of the lamp is constant.
D. The voltage is constant, the current is smaller, and the lamp is dimmed.
(09 Fuzhou) 13. As shown in Figure 5, it is the schematic diagram of the pressure sensor designed by Tong Tong, in which the upper end of the spring is fixed with the slider P of the sliding rheostat, there is a retractable wire between AB, and R 1 is a fixed resistor. When the switch S is closed and the pressure F increases, the changes of ammeter and voltage are shown as follows.
A. the current means bigger, and the voltage means smaller.
B. Current means smaller, and voltage means larger.
C. The ammeter and voltage indicator are relatively large.
D. the ammeter and voltage indicator have become smaller.
(09 Ningbo) 14. As shown in the figure, R is a magnetic resistance, and its resistance can increase with the enhancement of the surrounding magnetic field. When the magnetic field around the reluctance R increases, the switch S () is closed.
A. the current representation becomes smaller.
B. the voltage representation becomes smaller.
C. the light l is on.
A: A.
(09 Yantai) 10. In the circuit shown in fig. 7, the supply voltage remains constant. When the slider P of the sliding rheostat slides to the right after the switch is closed,
A. current means decrease, and voltage means decrease. B. Current means constant, and voltage means constant.
C. current means increase and voltage means decrease. D. Current means decrease and voltage means increase.
Answer: b
(09 Huzhou). After observing the automatic altimeter on the market, Xiao Ming designed the following four circuits (in which R' is a sliding rheostat, R is a fixed resistor, and the voltage at both ends of the power supply is constant). Among them, the higher the height, the greater the voltage representation.
Answer: b
(09 Jining) 8. In the circuit shown in fig. 6, the resistance value of R 1 is10Ω, the ammeter indicates 0.3A when the switch s 1 is closed and 0.45A when the switch S2 is closed, so the resistance value of R2 is Ω.
Answer: 20
(09 Lishui). As shown in the figure, there are two resistors with resistance values of 5 Ω and10 Ω in the dotted box. Xiao Ming wanted to know the connection mode, so he tested it with 3V power supply, ammeter and switch. After closing the switch, the ammeter reads 0.2A. Then, the two resistors are connected as follows. If you want to increase the reading of ammeter, you can take the following measures.
Answer: Increase the voltage in series or connect only one resistor or connect two resistors in parallel.
(09 Yiwu 2A 20. As shown in the figure, the power supply voltage is constant, and the words "2A20Ohm" are marked on the sliding rheostat. In the following four pictures, the relationship between the current I flowing through the small bulb L when the switch S is closed and the resistance R of the sliding rheostat connected to the circuit can be correctly expressed.
Answer: d