On the eighth day of the eighth grade, both answers in the science exercise book should be AB.

1 where is the water saving?

1.( 1) Ocean water glaciers and permanent snow-covered groundwater (2) Ocean water groundwater (3) Glaciers and permanent snow-covered groundwater (4) are incorrect. The water we use every day is mainly river fresh water, but the fresh water reserves in the earth's water bodies are very small. 2.C 3。 Water 4. (1) C (2) This view is incorrect, because pollution will be transferred to other water bodies through water circulation. 5.( 1) ① precipitation ② evaporation ③ water vapor transport ④ plant transpiration (2) water cycle 6. Living things can't live without water. In the water-deficient environment, some organisms can adapt to the water-deficient environment through automatic adjustment.

The second water-saving ingredient

1. Solid-liquid gas sublimation, melting and liquefaction 2. Right oxygen light blue hydrogen and oxygen water hydrogen+oxygen.

3.0℃ 0℃ 0℃ 4. Physical chemistry 5.d6.b7. Yes, put the wooden strips with Mars in the gas container, and it is oxygen that makes the wooden strips rekindle.

Third, the density of water saving

( 1)

1.(1)1.51.5 (2) 22 (3) Omit (4) mass to volume ratio (5) proportion ratio 2. A certain density ρ 3. The mass of copper with a volume of 1 m3 is 8.9×103kg8.94.c5.a6.c7.b8.c9. (1) The ratio of mass to volume of the same substance is constant (2) 1 and.

(2)

1 .2. Mass and bulk density 3.4743

4.b5.c6.c7 Gasoline

8.( 1) Solution:

Answer: The density of oil is 0.82× 103kg/m3.

(2) Solution:

A: The loading quality is 2.46× 104 kg.

9.V = 9m× 6m× 3.5m = 189m3

A: The classroom air quality is about 243.8kg..

10. (1)10g (2)11.25g (3) The selected titanium alloy has a relatively small mass of 31.25g..

(3)

1. mass and volume 2. It can reach 3.77.4g, 30cm, 32.58x103kg/m 34. C5.0.7× 1036。 ( 1) BACD (2)

Fourth water saving pressure

( 1)

1. Vertical surface 200 2. Pressure size stress area pressure unit area pressure stress area pressure 3. Nm 2 Pascal Pappa 4. Reduce the stress area and increase the pressure by 5. Pressure leveling 6.C7.C8. (1) When the stress area is constant, the greater the pressure, the greater the pressure. (2) When the pressure is constant, the smaller the stress area, the greater the pressure. (3) The magnitude of pressure and stress zone is 9. 1.96× 104 Pa instead of 10. There are two mistakes: one is the stress area s; The second is the pressure f, and the correction value is as follows: s = 0.1m× 2m× 2 = 0.4m2f = 620np =1.55x103pa11.3x/kloc.

(2)

1.( 1) Reduce stress area and increase pressure (2) Increase stress area and decrease pressure (3) Increase stress area and decrease pressure.

2 . C3 . a4 . b5 . a6 . C7 . a 8 . 4 . 6× 105 pa 9 . 0 . 82 m2

10.( 1)600N(2)0.2 m2(3)3.2× 104 Pa 1 1。 ( 1) 600g (2) 1.7。

(3)

1. The liquid has pressure on the bottom of the container and the liquid has pressure on the side wall of the container. 2. The greater the height difference, the greater the pressure of the liquid on the object put in it. At the same depth, the greater the pressure of liquid in all directions.

3.B4。 A 5。 Convex upward, horizontal, convex downward, convex upward 6. (1) A, b, C (2)E, F (3)B, d, e (or c, d, e or a, d, e)

7.3, 4 and 5 At the same depth, the pressure of liquid in all directions is equal.

5、6

8. It is equal to the depth of the metal box immersed in the liquid, and the depth of the metal box immersed in the liquid is small.

Fifth, the buoyancy of water saving.

( 1)

1.D

2. Buoyancy of water

3. Gravity balance force

2.3 Vertical upward

5.( 1) 6.75 2.5 (2) Relevance (3) C.

(2)

1. An object immersed in a liquid is subjected to upward buoyancy, which is equal to the gravity of the liquid displaced by the object. 2. Same, same, same. 3.( 1) 36 (2) Liquid density (3) 1566 4.9.85. C6 b7。 (1)1.50.438+0.90.50.5. The buoyancy of stone is equal to the gravity of boiling water. 8.( 1) B (2) 700 cows (3) 70kg 9.1.26kg/m3 10. About 0.5N

(3)

1. Less than 2. b3。 Bigger and unchanging 4. Greater than or equal to 5. d6。 (1) 0.5 (2)11.5 Gravity of discharged water (3) 7. l 1 >； L0, L2≈L0. The rubber band is stretched to L 1 under the tension of water. Because the gravity of the plastic bag can be ignored, after the plastic bag is immersed in water, the rubber band is almost unaffected by the buoyancy of water, and the rubber band returns to its original length L0. 8. The judgment is based on the fluctuation of the object 9.0.2025 kg 10. (1) 0.6 zero (2)0.04 kg.

Section 6 Dispersion of Substances in Water

1. Solute solvent 555502. B3.1254637 4.d5.a6.c7.a8.d9. No gasoline, alcohol, acetone 10. Measuring cylinder balance glass rod 136 36 100 At a certain temperature, the amount of a solute dissolved in a certain amount of solvent is limited:11.41and three (or two plus four) and two (or three). Mainly manifested in the stimulation of human skin and eyes. The environmental impact is mainly manifested in the eutrophication of water bodies and the destruction of aquatic ecosystems.

Section 7 Dissolution of Substance in Water

( 1)

1.b 2。 Unsaturation 3. The concentrated solution and dilute solution are 4.36 grams and 5.202 6 respectively. The saturated dilute solution is not necessarily 7. C8.D9.A 10。 A 1 1。 D 12。 You can flush more water; Wash the medicine with hot water as much as possible; Drink the first dose before flushing, etc. 13.c 14。 The dissolution rate of (1) is related to the particle size. (2) Different substances have different solubility. (3) Heating can improve the solubility of salt, but the extent is not great.

(2)

1. Properties and temperatures of solutes and solvents 2. Add or subtract 3. (1) At 20 t 1℃, 20g of substance A was dissolved in 100g of water, just saturated with (2)B (3). A C A increase or decrease by 4.80g 5.32 100 6. C7.A8.20g 9。 Pressure and temperature 10. ( 1) ② ① (2) 0.024.

(3)

1.52.20 % 3.0 . 54.54 . 2.550ml 47.55 . C6 . C7 . a 8.9g 9。 ( 1) 1g(2)5800g 0.0 17% 65438。

Section 8 Crystallization of Substances in Water

1. Conventional melting point 2. Evaporating the solvent cools the hot saturated solution. The temperature of evaporated solvent sugar water decreases, and the solubility decreases. 5.c6.a7.b8. Salt and other substances are dissolved in human sweat. After sweat is stained on clothes, with the evaporation of water, solute crystals such as salt will form white patterns. 9.B 10。 The solubility of (1) sodium chloride in soda ash is less affected by temperature, while the solubility of soda ash decreases obviously with the decrease of temperature. (2) The solvent evaporates in summer.

Ninth, the utilization and protection of water saving.

( 1)

1.B2。 D3。 Time and space: Xiajiang runoff flows south, north, east and west. 4.( 1) 17 liters (2) saving water is homophonic with receiving water, which means saving every drop of water (3) omitted.

(2)

1.A2。 D3。 C4。 Precipitation, filtration, distillation and distillation of distilled water. The filter plate, funnel, glass rod, beaker and filter paper are broken or the filtrate is higher than the edge of filter paper (1). Glass rods are not used for drainage (2) The edge of the filter paper is higher than the edge of the funnel (3). The end of the funnel is not close to the inner wall of the beaker. 6.( 1) B (2) D (3) filtration (4) is not 7. (1) crystallization (2) filtration (8). D9。 B 10。 Vaporization and liquefaction.

Review exercises

1.A 2。 D 3。 A 4。 C 5。 D 6。 C 7。 An eight. B 9。 B 1O。 D 1 1。 C 12。 A 13。 D 14。 C 65438+ 05。 C 16。 (1) ocean water, land fresh water, glacier water and underground fresh water (2) ocean water and glacier water 17. Oxygen, hydrogen, hydrogen and oxygen 18. Increase the equal density 19. The gravity of the liquid discharged upward is 20. The increment is constant 2 1.2.5 × 104 22. (1) Unsaturation (2) Increase the temperature or add water 23. (1) Solute solvent (2) Relationship between solubility and temperature 24. With the increase of salt water density, potatoes will float but not sink. The error is greater than 25. (1) benzoic acid has little solubility at room temperature. (2) Benzoic acid is dissolved in large quantities at high temperature. (3) slowly cooling to room temperature. 26. Increase or decrease of (1). (2) is equal to (3) 2 10.527.0.9× 65438+. P0, therefore, the pressure of the vehicle on the road surface exceeds the specified value (2). Excessive pressure damages the road surface, the mass of the vehicle is too large (the inertia of the vehicle is large), it is difficult to control, and traffic accidents are prone to occur. 30.( 1) The distance h from the water surface to the "0 N" scale line is directly proportional to the weight g (2) 7 (3)10 n.

Chapter 2 Earth's "coat"-atmosphere

Section 1 Atmosphere

1.10002. (1) ① troposphere ② stratosphere ③ warm layer ④ outer layer (2) ① ③ ④ (3) The atmosphere has strong convection movement (4) ② 3.A4.A5.D6.B7.D8. (1).

Section 2 Weather and Temperature

1. Temperature and humidity. The temperature is hot and cold. The thermometer is 4 degrees Celsius (℃). The temperature of the highest and lowest day is constantly changing. (1) 2 pm before and after sunrise (2) Weather 6.D7.C8.A9. (7+ 15+65438+.

The third quarter atmospheric pressure

1. Atmospheric pressure 2. 10. 1 N 3. Speed and speed 4. C5.A6.B7.A8.B9.C 10。 c 1 1.9× 104 pa 65438。

The fourth quarter atmospheric pressure and human life

1 .atmospheric pressure 2. More than 3. Zero, MINUS 4. Increase boiling water, stop boiling and reduce boiling water. The boiling point of reboiler is related to air pressure. With the increase of air pressure, the boiling point rises by 5. D6。 C7.C8.B9.A 10。 A 1 1。 Reduce the increase of atmospheric pressure.

12.② ② ③ ⑤

Section 5 wind

1.( 1) × (2 )× (3) √ 2. Blow eight 3. A- northwest wind B- north wind C- northeast wind D- east wind E- southeast wind F- south wind G- southwest wind H- west wind 4. The airflow is level 5. B6.A7.D8.A。

Section 6 Why does it rain?

1.(1) × (2 )× (3) √ (4) √ 2. (1) Dry-wet difference: A-2 B-5 C- 1 D-3 E-4 F-5 (2) Relative humidity. D 4。 C 5。 A six. B 7。 (1) Domestic chickens like to be dry, and the henhouse is particularly wet before it rains, so they don't want to go into the henhouse early. (2) There is a lot of water vapor, and the ant nest is particularly wet, so it needs to be moved to another place to live.

What will the weather be like tomorrow?

1.( 1) is greater than15mm (2) 5 ~15mm (3) is less than 5mm. Meteorological information. (1) ups and downs, cold (2) cooling and rainy (4). C5。 B6。 B7。 ①1035②1005③10/0④10/5 (2) A high pressure B low pressure C low pressure D cold front E warm front (3) Rainfall, strong wind and cooling weather occurred in the area controlled by the air pressure system. (4) High pressure Yangtze River basin (middle and upper reaches) 8. (1) The green part represents land, the blue part represents ocean and the white part represents clouds. (2) The whiter the clouds are, the thicker the clouds are, and the places with thick clouds are generally rainy areas.

Section 8 Climate and Factors Affecting Climate

( 1)

1. Average condition and extreme condition 2. 256 1343. 1℃ specific heat capacity 4. (1) Lower north latitude position (2) Lower high temperature (3) Qinghai-Tibet Plateau 5. B6.b7.C8.d9 Heating time 10.

(2)

1. Difference 2. On the contrary, it is close to the opposite. 3.( 1) Northwest Southeast Monsoon (2) The ocean inside the mainland is cold and dry, with high temperature and rainy. 4.( 1) A (2) A (3) Warm and humid air is forced to climb along the windward slope when encountering terrain obstacles, and the water vapor in the air cools and condenses, so it will face the wind. On the leeward slope of the mountain, due to the sinking of airflow, the temperature is rising continuously, and there is less precipitation, so it is difficult for the air to reach supersaturation. 5. 1520m-720m = 800m 800×0.006℃= 4.8℃

28.8℃-4.8℃=24℃ 6.D 7。 B 8。 C

9.( 1) During the day, the temperature on land rises rapidly, and the sea surface temperature is relatively low; At night, the temperature on land drops rapidly, and the sea surface temperature is relatively high. (2) counterclockwise during the day and clockwise at night. (3) During the day, the temperature in coastal areas is lower than that in inland areas, which plays a cooling role.

Section 9 monsoon in eastern China and arid climate in western China

( 1)

1.( 1) ① temperate monsoon climate ② subtropical monsoon climate ③ tropical monsoon climate ④ temperate continental climate ⑤ plateau alpine climate (2) omitted 2. Prevailing wind: 8 Prevailing wind source: ③ ② Climate characteristics: 4555553. (1) omitted (2) southeast and northwest (3) southeast coast. However, the northwest region goes deep inland, and the summer monsoon can't reach it, so there is less precipitation. 4. D5.B6.B7.C8. (1) BCABBA (2) A temperate continental climate B tropical monsoon climate C plateau alpine climate D temperate monsoon climate E subtropical monsoon climate (3)AC annual precipitation is below 400 mm

(2)

1. Cold wave typhoon flood 2. Cold air and high pressure. Continuous rainstorm typhoon 4. (1) Hundreds of typhoons (2) Typhoon eyes are calm and clouds rarely sink (3) Storms (4) will cause strong winds, heavy rains and storm surges, and damage buildings such as trees and houses. 5.A-⑤ b-⑤ c-⑤ d-⑤ e-⑤ c 7.c 8。 Burning a lot of energy, such as coal, oil and natural gas, and cutting down a lot of forests. 9.( 1) Because the urban population is concentrated and the industry is developed, residents' lives, industrial production and vehicles consume a lot of fuels such as coal, oil and natural gas every day, releasing a lot of heat, which leads to the higher temperature in the city than in the suburbs and makes the city like a warm island. (2) The air rises in the city and sinks in the suburbs, and the descending airflow flows from the suburbs to the city center. (3) Omission

Review exercises

1.A 2。 D 3。 C 4 explosive D 5。 C 6。 C 7。 B 8。 D 9。 C 10。 B 1 1。 D 12。 C 13。 C 14。 C 65438+ 05。 C 16。 Small and large, 17. The atmospheric pressure outside the bottle is greater than that inside the bottle, 18. The latitude position is 19. The blowing wind is 20. Land and land are 2 1. The pressure decreases and the pressure increases. Solar radiation is very low. Height 23. Bubbles should be from small to large 24.4000 25. (1) The high-pressure weather is fine, and the low pressure is rainy. (2) The cold front is cloudy and rainy, and the wind cools down. (3) The northwest wind is 26.b27. (1) 2000 m a (2) The windward slope is 28. (66) Mountain height (2) Latitude difference (3) Coastal and inland difference 29. About 30. 106 Niu 3 1. The pressure cooker takes a long time from boiling water to boiling water. The reason why we say "fast" is because the air pressure in the pot raises the boiling point of water, thus shortening the time from boiling water to cooking. 32.omission

Chapter III Adjustment of Life Activities

1 section the influence of environment on biological behavior

1 .rhythm 2. (1) Weather (humidity, air pressure) (2) Light (3) Temperature (season) 3. (1) hydration of water (2) (3) touches 4.D5 Left and right chemical control 6.D7.C

The magic hormones in the second quarter

( 1)

1.( 1) is long and curved, neither long nor curved.

(2) grow and bending that apical base relate to the apical end of the embryo.

(3) Only long and not bent, both long and bent

(4) Bending growth is related to whether the embryo top is exposed to unilateral illumination. 2.( 1) Are there any substances at the embryo tip that can promote the bending of plants?

(2) The experiment used to compare (3) is as follows.

3. Gibberellin cytokinin

4. Blood sugar 90 mg/100 ml

5.D 6。 B D 7。 C

8. Excessive insulin makes the blood sugar concentration too low. Glucose.

9.( 1) Insulin (2) lowers blood sugar

(2)

1. Catheter hormone circulation system 2. A 3。 B 4。 B 5。 B 6。 Omit 7. It shows that thyroid hormone can promote the development of tadpoles. 8.( 1) Omit (2) sex hormones. Secreted by human gonads.

The third nerve regulation

( 1)

1. nervous system 2. Neuron photoreceptor cell olfactory cell taste cell 3. (1) Dendritic axon protruding from cell body (2)A Dendritic B nucleus C axon D axon branch 4. (1) A brain b cerebellum c brain stem (2) auditory pathway (3) cerebellum (4) brain stem 5. A6.A7.C8.B9.A 10。 D 1 1。 A 12。 Life centers such as cardiovascular movement center and respiratory center of human body are concentrated in the brain stem, which is located at the back of the brain, so

(2)

1. Reflex receptor afferent nerve center efferent nerve 2. C3。 B4。 (1) A Effector B Efferent Nerve C Spinal Cord D Afferent Nerve E Receptor (2) Receptor Effector (3)E D C B A (4)A (5) The reflex activity of spinal cord is controlled by the brain (6). The reflex conduction or transmission of information to the brain. Auditory efferent nerve effect of auditory nerve (or afferent nerve) 6.c7.b8.c9. (1) Physical exercise and manual labor (2) Omission (3) Omission.

Section 4 Animal Behavior

1. Neurohormone. Innate instinct cerebral cortex acquired learning behavior cerebral cortex 3. Language and writing. D5 D6 . a7 . A8 . d9 . d 10。 B 1 1。 (1) nervous system (2)

Section 5 Temperature Control

1. Skeletal muscle visceral skeletal muscle 2. The skin radiates heat directly, and sweat evaporates 3. Heating and heat dissipation 4. A5.D6.D7.C8.C9. Increase of heat generation and heat dissipation 10. (1) A is higher than (2) Diastolic height increases (3). Sweat evaporation c11.d12.d13.c.

Review exercises

1.A2。 D3.B4.D5.B6.B7.C8.D9.A 10。 D 1 1。 The growth of plants at the tip of the germ. The development of fruits prevented the flowers and fruits from falling, and inhibited the growth of plants 12. Blood sugar 90 mg/ 100 ml 13. Endocrine hormone vascular blood circulation 14. Reflective reflex arc 15. Congenital behavior acquired learning behavior nervous system 16. The number of receptors increased by 17. (1) afferent nerve center efferent nerve.

A, G (3)C Spine Skeletal Muscle 18. It shows that the roots are located in different parts when the seeds germinate, which proves whether the roots grow directionally. 19. The light from the earth's gravity to the ground side affects the distribution of auxin, which makes the stem on the opposite side grow faster. 20.B2 1。 (1) conclusion. Reason: The rate of blindfolded bats successfully avoiding obstacles is basically the same as that of blindfolded bats. (2) Conclusion: Hearing is very important for bats to avoid obstacles. Reason: The rate of successfully avoiding obstacles is only half that of blindfolded bats. (3) Conclusion: Two ears are very important for bats to avoid obstacles. Reason: Although one ear was blindfolded and the other ear could hear, the proportion of successfully avoiding obstacles was basically the same as that of bats blindfolded. (4) Conclusion: It is very important for bats to emit ultrasonic waves to avoid obstacles. Reason: Bats with their mouths covered successfully avoid obstacles like bats with their ears covered when they can't emit ultrasonic waves. (5) Bats rely more on hearing to avoid obstacles, which is beneficial to them, because bats come out at night, the light is dim, and the role of vision is reduced. 22.( 1) Visceral skeletal muscle (2) Exercise and eat hot food such as hot pot or water. 23.( 1) Spiders are born with the behavior of weaving webs. (2) There is no direct relationship between B bell and eating, and dogs can establish a certain relationship between them through long-term training. 24.b Diabetes patients have insufficient insulin secretion and high blood sugar concentration.

Chapter 4 Circuit Exploration

Circuit diagram in section 1

1. Power switch line 2. a，C，B 3。 Series and parallel connection. Parallel L 1 and L2L2 5. C6。 A7。 D8。 Parallel schematic diagram 9. Draft 10. D.

Current measurement in the second quarter

1. The movement direction of positive and negative electrons and electrons is Amp A mA 2. A3.0. 1.24。 Series positive terminal negative terminal 5.320 ~ 3a1a0.1a0.5a0.52a0 ~ 0.6a6. Current of lamp L 1 The main current of lamp L 1 branch is 7. C8.A9.B 10。 B 1 1。 A 12。

Section 3 Conductivity of Substances

1. Conductor insulator 2. Steel ruler, metal compass, rubber, plastic ruler etc. 3. Conductor, conductor and insulator 4. Command 5. Electrons move freely. The blocking current R ohm ω kiloohm Megaohm 7. 1.963 0.00 1963 8. C9.A 10。 D 1 1。 Schematic diagram of conductive metal sheet 65438. Because of its good conductivity, the price is much lower than that of silver. (2) Metals with good electrical conductivity have good thermal conductivity.

Section 4 Factors affecting the size of conductor resistance

1. The increase of the cross-sectional area of the material length decreases the superconductivity 2.0.0175 Ω Ignore 3. The copper wire has a small resistance 4. Different sizes 5. B6.C7. (1) AC (2) CD (3) BC 8. (1) 6666 3 and 6) (2) When the material and cross-sectional area are the same, the longer the conductor, the greater the resistance; (3) When the material and length are the same, the greater the cross-sectional area, the smaller the resistance.

Section 5 Rheostat

1. Resistance wire length current of sliding rheostat 2. A B B terminal becomes smaller by 3. AP gets longer, bigger and darker, BP gets shorter, smaller, bigger and brighter. C 5。 B 6。 A seven. Slightly 8. (1)AB two terminals (2)① AC or BC terminals are connected in series. ③ The position with the greatest resistance ④ The positions with the greatest resistance (3) and (4) are omitted from the figure.

Section 6 Voltage Measurement

1. Voltage supply volt kilovolt millivolt 2. 1.5 volt 3 volt 220 volt 3. 10-4 106 4. Dark light 5. (1) voltmeter is combined with 320 ~ 3 volts 0 ~ 15 volts (2). 2 volts 12.5 volts 0.6 volts 6.0 ~ 3 volts 0 ~ 15 volts cannot be 7d8.b9.b10.b1.12.2000 ~ 5333.

Section 7 Relationship between Current, Voltage and Resistance

( 1)

1. The voltage across this conductor. Resistance experiment of this conductor. 2. Voltage resistance. Voltage and current resistances across the voltage resistor. 3.( 1) omitted. (2) The voltage is directly proportional and the obstruction is inversely proportional. 4.0.32 A 25 Euro 25 Euro 5.4.5 A 6.6 V 7. 10 Euro 8. The current through the ammeter reaches 75 A. 9.85.7 Ampere 428 times 10. C

(2)

1.a2. (1) Voltmeter and ammeter voltammetry (2) Power supply voltmeter and ammeter change current (3) Omit (4) Maximum and minimum value (5) Increase and brighten (6)0.5 4 8 ohm (7)8.3 7.7 6.8 5.6 Figure Omit (8) Change with voltage. 3.( 1) CDEBFA (2) omitted.

Section 8 Circuit Connection

( 1)

1.B2。 Parallel and series. The water flows through a, b and c may be equal. 4. The currents in different series circuits of A, B and C bulbs are equal. 5.( 1) ABBC AC (2) Omit (3) The total voltage on the series circuit is equal to the sum of the voltages on the series conductors. (4)2 volts. 6. It is as big as 7. (1) omitted (2) 1.5 volts. (3)①② (4) The resistance of lamp L 1 and L2 should be different. 8. The voltage between 8.BC was misread in the second measurement, which should be 65438.

(2)

1.d2.a3.d4. (1) Omit (2)Ia=Ib=Ic (3) The current of the main circuit in parallel circuit is equal to the sum of the currents of each branch (4) 0.2A 1A5. O.220.25 6。 Can be used at the same time. 7.

Review exercises

1 . D2 . D3 . C4 . a5 . D6 . C7 . A8 . d9 . c 10 . d 1 1。 Parallel insulated wires will not be connected in series 12. Control variable resistance voltage 65438+ 03. The filament resistance increases with decreasing the temperature rise 14. AP series increases, decreases and darkens 15. Cu-ni-Cr alloy 16. It becomes bigger and bigger from 17. Left 103 18. Omit 19. (1) volts. Zoom in 20 times. (1) slightly (2) out of proportion (3) gradually reduced by 2 1. This experimental scheme has three shortcomings: ① the power supply voltage exceeds the bulb voltage; ② Only a group of bulbs with the same specifications were selected; ③ It is not appropriate to draw a conclusion based on only one measurement data. Improvement measures: ① Choose two dry batteries in series as power supply or add sliding rheostat; ② Different groups of bulbs were selected for experiments; ③ We should analyze the experimental data measured many times and draw a conclusion. 22.( 1) Where the resistance is the largest, (2)B (3) Close the switch, adjust the rheostat slider, read the readings of the voltmeter and the corresponding ammeter at both ends of the fixed resistance respectively, and compare how the ratio of voltage to current changes each time. ④ Control variable 23. The resistance is 3 Ω and the power supply voltage is 3V24. (1) small.