The physics final exam paper of the ninth grade last semester contains the answer. 1. Multiple-choice questions (There are four options for each of the following questions, of which only one option for 1-9 meets the meaning of the question, with 2 points for each question; 10- 1 1 The question has more than one option that meets the meaning of the question, and each small question will get 3 points. )
1, as shown on the right, in the process of boiling water on a natural gas stove with aluminum pot ().
A. the higher the water temperature, the more intense the movement of water molecules.
B. change the internal energy of water by doing work.
C the specific heat capacity of aluminum is smaller than that of water, and the heat absorption capacity of aluminum is stronger than that of water.
D. The more fully natural gas is burned, the greater its calorific value.
2. In the following example, the internal energy of an object is increased by doing work ().
A. The hand holding the thermos gets warmer. B. The metal spoon in the hot soup gets warmer.
C. When sawing wood with a saw, the temperature of the saw blade rises. D. After the hot metal sheet is inserted into the water, the water temperature rises.
3. Use two identical electric heaters to heat substance A and water with the same mass, and the relationship between its temperature and heating time is shown in the right figure, so it is judged that the specific heat capacity of substance A is ().
A.2. 1× 103J/(kg？ ℃) B.4.2× 103J/(kg？ ℃)
C. 1.2× 103J/(kg？ C) D. the conditions are insufficient and cannot be determined.
4, the following statement about the conductor is correct ()
The greater the current through the conductor, the smaller the resistance of the conductor.
When there is no current in a conductor, it has no resistance.
C the voltage at both ends of the same conductor increases several times, and the current passing through it also increases several times, and the ratio of voltage to current remains unchanged.
D. the conductor conducts electricity through free electrons.
Xiaoyun's bathroom is equipped with ventilator and lighting. The circuit connection between the ventilator and the lighting lamp is shown in the picture on the right. The following statement is correct ().
A. ventilator and lighting cannot work at the same time.
B. The ventilator and lighting can only work at the same time.
C. When the ventilator and the lighting lamp are working, the current passing through them must be equal.
D. When the ventilator and the lighting lamp are working, the voltages at both ends must be equal.
6, as shown in the figure below, conform to the principle of safe electricity is ().
7. In Figure A, the rated voltage of the small bulb is 6V. Connect the resistance wire AB with uniform thickness (its resistance value does not change with temperature) into the constant voltage circuit at both ends of the power supply through the slider P. When the switch S is closed and the slider P slides from the leftmost end A to the rightmost end B, the I-U relationship image of the small bulb is shown in Figure 8B. When the power consumed by the small light bulb is 2.8W, the following resistance values are closest to the resistance value of the resistance wire AB connected to the circuit at this time ().
A. 1ωb . 3ωc . 5ωd . 6ω
8. In the circuit shown on the right, the voltage at both ends of the power supply remains unchanged, and when the switch S is closed, the lamp L emits light normally. If you slide the slider p of the sliding rheostat to the left, the following statement is correct ().
A. The indicator of the voltmeter becomes larger and the lamp L becomes brighter.
B. The indicator of voltmeter becomes smaller and the lamp L becomes dim.
C. the indicator of voltmeter becomes larger, and the light l becomes dim.
D. The indicator of the voltmeter becomes smaller and the lamp L becomes brighter.
9. In the circuit shown on the right, the power supply voltage is 6V. Only switch S 1 is closed, and the current is 0.2A Then switch S2 is closed, and the current is 0.6A The electric power consumed by R 1 before and after switch S2 is closed is different ().
2W。 0W C. 1。 2W D2 . 2W
10, the following statement about the law of series-parallel circuit is correct ().
A. A circuit with equal voltage at both ends of each electrical appliance is a parallel circuit.
B the total current of parallel circuits is equal to the sum of currents of each branch.
C. The disconnection of one electrical appliance in the parallel circuit will not affect the normal operation of other electrical appliances.
D. A circuit with equal currents through all electrical appliances is a series circuit.
1 1. Connect two bulbs labeled "6V 3W" and "12V 6W" in different circuits, ignoring the influence of temperature on the lamp resistance. The following statement is correct ().
A. When both light bulbs emit light normally, the currents flowing through the two lamps are equal.
B. When two light bulbs are connected in series to a power supply with appropriate voltage, only one lamp can emit light normally.
When two bulbs are connected in parallel to a 6V power supply, the "6V 3W" lamp consumes more power.
D. When two bulbs are connected in series on the power supply of 12V, the power consumption of "12V 6W" lamp is relatively large.
Two. Fill in the blanks (12- 16 is 1, 17- 19 is 2).
12. Smelling the fragrance of jasmine is a _ _ _ _ _ phenomenon, which means _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.
13, the calorific value of gasoline is 4.6× 107J/kg, and the heat released by complete combustion of 2kg gasoline is J.
14、5kW？ H can be used for an incandescent lamp marked "220V 25W" to work normally.
15, many people once fantasized about being a perpetual motion machine, which can continuously do work outside without power. The fundamental reason why this idea can't be realized is that it violates the law.
16. In the circuit shown in the figure, the power supply voltage is constant, R 1 is a constant resistance, the maximum resistance of the sliding rheostat is R2, R 1=2R2, and the word "12V 9W" is marked on the bulb L. When S 1, S2, By turning on or off the switches S 1, S2 and S3, the position of the slider P of the sliding rheostat can be changed, so that the power consumed by the circuit in a certain state can be minimized, and the minimum power value is P= W (ignoring the influence of temperature on the lamp resistance).
17, Oster found that there is a magnetic field around the electrified wire, which is called current effect.
18, two fixed-value resistors A and B are marked with "16Ω1.5a" and B is marked with "22ω0.5A". Now they are connected in series. In order to ensure the safety of the resistor, the maximum voltage allowed at both ends of the series circuit is V.
19 As shown in figure 1 1, the resistor R is connected to the small light bulb in the circuit. When the switches S 1 and S2 are closed, the resistance R is _ _ _ _ _ _ _, and the electric power of the bulb is 9W. When S 1 is turned off and S2 is turned on, the electric power of the bulb is 1W (regardless of the change of the resistance of the bulb with temperature), so the electric power consumed by the resistor R at this time is _ _ _ _ _ _ _ _ _ _.
Three, painting questions (2 points each)
20. The compressor of the refrigerator and the light bulb of the refrigerating room do not affect each other when working. The compressor is controlled by the temperature control switch, and the light bulb is controlled by the door control switch. Please draw the working circuit diagram of the refrigerator.
2 1, the electric wire is replaced by a stroke line, and the electric lamp and the switch controlling it are correctly connected to the home circuit in the figure.
20 theme map 2 1 theme map
Four, experimental inquiry questions (5 points +6 points +6 points)
22. In order to compare the heat absorption capacity of water and sand, Xiaowen did an experiment as shown in the figure: two identical beakers filled with water and sand respectively and heated with two identical alcohol lamps. The experimental data are recorded in the following table:
(1) Should water and sand be controlled before the experiment? _ _ _ _ _ and _ _ _ _ are the same.
(2) In this experiment, it is used to indicate how much heat is absorbed by water and sand;
(3) By analyzing the experimental data in the table, we can know that the heat absorbed by water and sand with the same mass will be the heat absorbed by sand at the same temperature (optional: "greater than" or "less than");
(4) Water and sand with the same quality will be heated for the same time, and the temperature will be higher (choose "water" or "sand").
23. Xiaoyan uses "Voltammetry" to measure the resistance of constant resistance R. ..
(1) Please add a conductor to complete the physical diagram shown in Figure A;
(2) Before the experiment, turn on the _ _ _ _ _ switch and put the slider P of the sliding rheostat in Figure A at the extreme (select "left" or "right") end;
(3) After checking that the circuit is connected correctly, close the switch S. When the slider P of the sliding rheostat slides to a certain position, the voltmeter indicates as shown in figure 16B, and the ammeter indicates as shown in figure C, then the voltmeter indicates as V, the ammeter indicates as A, and the resistance value of the resistor R is? .
24. In order to explore the relationship between heat generated by current and resistance, Xiao Wei adopted an experimental device as shown in the figure, in which R 1.
(1) The reason why bottles A and B contain liquids with the same quality and initial temperature is _ _ _ _ _ _ _ _ _ _.
(2) In the experiment, the connection method of R 1 and R2 (fill in "series connection" or "parallel connection") is to control _ _ _ _ _.
(3) When the power-on time is the same, the kerosene in the two glass tubes rises higher (fill in "A" or "B"). Therefore, _ _ _ _ _ _ _ _ _ _ _
Five, comprehensive application problems (6 points +6 points +9 points)
25. Students from the physics interest group did an experiment: put 500g of water in a beaker, and the water temperature was measured to be 20℃. Then they lit the alcohol lamp to heat the beaker, inserted a thermometer into the water, and observed the change of water temperature. When the pointer of the thermometer is just 70℃, it consumes 65,438+00 grams of alcohol. [C water = 4.2× 103 Joule℃)]
(1) Please calculate how much heat water absorbed in the experiment?
(2) Some students tried to use the heat absorbed by water to calculate the calorific value of alcohol. Please answer, is this ok? And explain why.
26. As shown on the right, it is a typical circuit of hair dryer with rated voltage of 220V, in which the heating wire can generate heat after being electrified, and the motor can supply air after being electrified, and the rated power of the motor is 120W.
(1) When sending cold air, the selector switch should be placed in the _ _ _ _ _ _ position; To transport hot air, the selector switch should be placed in the _ _ _ _ _ position. (Fill in "A", "B" or "C")
(2) If the blower works at rated voltage, what is the work done by electrifying for 8min when sending cold air?
(3) If the blower works at the rated voltage and the total power consumed by the circuit when sending hot air is 560W, what is the resistance of the heating wire R?
27. In the circuit shown in the figure below, the power supply voltage remains unchanged, and the bulbs L 1 and L2 are marked with the words "6V 3W" and "6V 6W" respectively. If the switch S 1 is turned off and S2 is turned on, only one light bulb will emit light normally; When switch S 1 is closed, switch S 1 is closed when S2 is closed. When S2 is turned off, assuming that the filament resistance does not change with the temperature, the indicating ratio of the ammeter is 2∶3. Q:
(1) When switch S 1 is off and S2 is closed, the readings of voltmeter and ammeter;
⑵ Maximum electric power and minimum electric power consumed by the circuit.
Reference answer:
First, multiple choice questions
1-5:ACACD； :6-9:BBCAB； 10: BC; 1 1: automatic call distributor
Second, fill in the blanks
12, diffusion, molecules are constantly doing random motion;
13、9.2× 107;
14、200;
15, energy conservation;
16、 1.5;
17, magnetic;
18、 19;
19, short circuit, 2;
Three, drawing questions (omitted)
Fourth, experimental inquiry questions
22, (1) mass, initial temperature; (2) heating time; (3) greater than; (4) sand;
23, (1) omitted; (2) disconnection and correctness; (3)2.6、0.26、 10;
24. (1) It is convenient to increase the number of reaction resistance wires with a thermometer to release heat; (2) Series connection, current and power-on time; (3) When the current and the power-on time are the same, the greater the resistance, the more heat generated by the current;
V. Comprehensive application problems
25、( 1) 1.05× 105; (2) No, because there is heat loss, the heat released by alcohol combustion cannot be completely absorbed by water;
26 、( 1)B、A； (2)57600j； (3) 1 10Ω;
27. (1)6V, 0.5A (2), 6.75W, 2.7W.