1 acousto-optic
1. 1 Ears and audible sounds
Lesson 65438
1, 1 .D 2。 C 3。 A
2, 1.√ 2.√ 3.X4。 X5。 X6。 √ 7.√ 8.
1 vocal cord vibration vocal cord 2. Vibration 3. Vibration 4. The sound generator (sound source) vibrates 5. Drum surface vibration 6. Tuning fork vibration 7. Air vibration 8. Water waves propagate sound waves. Energy information 10. Water vibration 1 1. Feima yellow river water
Fourthly, (1) are all caused by the vibration of the air column in the musical instrument. (2) The vibration of the strings drives the vibration of the air column in the * * * resonance box, thus producing an amplified and purer sound. (3) The solid vibrates by knocking.
(4) The answer is not unique, as long as it conforms to the principle of sound production.
second kind
1， 1 . B2 . B3 . D4 . b5 . B6 . B7 . D8 . B9 . b。
2， 1.x2.√ 3。 √ 4.√ 5.√ 6.x (Hint: You can't hear sound without normal hearing devices or sound transmission media. )7，7，X 8。 √9.√ 10.X
Three, 1. Air, water and liquid II. Vibrating vacuum 3. Water can transmit sound. Solid sound transmission gas sound transmission 5. Sound collection and sound transmission function. Water pipes, tap water, air 7. I can't help but make a sound with a normal medium ear. Tympanic membrane, cochlea and auditory nerve 9. Medium, air vacuum, no medium (no air on the moon), different from 340 10. Air liquid (water
Advantages: (1) There is no sound transmission medium in the vacuum glass, which can cut off the passage of outdoor sound into the room and realize indoor noise prevention; (2) It can be insulated without affecting lighting, etc.
5, 1. Fill in the form: the sound you hear next to you is solid (table).
The sound heard when there is a gap is transmitted by air.
Your conclusion: the sound transmission effect of the table is better than that of the air.
2.( 1) The experimental phenomena that can explain the sounding conditions are as follows: ① ④ The object vibrates and sounds.
(2)① It shows that vacuum cannot transmit sound, but air can transmit sound or sound needs medium.
(3) It shows that the length of vibrating air column affects sound production. (To be precise, the vibration speed and frequency of air columns with different lengths are different, which makes the tone of sound different. This knowledge point will be studied in the next section. )
The third category
1、 1 . a2 . C3 . a4 . b5 . D6 . C7 . b8 . C9 . b 10 . d 1 1 . b 12 . c。
13.B 14。 B 15。 C 16。 B 17。 A
Multiple-choice analysis 10: the connotation of maintaining realistic effect of audio equipment is: (l) the components of reproduced sound in each frequency band are the same as the original sound, that is, the spectral characteristics are the same; (2) The loudness and dynamic range of the reproduced sound can be compared with the original sound; (3) The reverberation characteristics of the original sound are preserved in the reproduced sound; (4) Reproduce the spatial characteristics of the original sound; (5) No new noise is introduced, so D is selected.
2, 1.X 2。 X 3。 X 4。 √ 5.X 6。 X 7。 √
Third, 1. Stethoscope can reduce sound dispersion, keep the loudness of ears as constant as possible, and reduce environmental noise interference.
2. Low, big, high and small 3. Bird ox amplitude (amplitude) timbre 4. Tone loudness 5. Loudness, high pitch and good timbre 6. Prevent noise generation, block noise propagation, and prevent noise from entering human ears. Tone loudness 8. Amplitude loudness 9. When the amplitude is increased, the loudness of human ear increases 10, timbre increases 1 1, pitch increases 12, noise increases 13, and the propagation distance of amplitude sound increases 15. dB dB 0 dB。
16. Loudness 17. 20 Hz~20 000 Hz 400 Hz can 18。 Slow, small and low 19. The distance between sound source with large amplitude and human ear is 20. Affect people's normal rest, study and work 2 1. Tone loudness timbre frequency.
Frequency 22. Tight, short and thin
4. 1. (1)340 (2) Noise
2.( 1) You can ask questions from the perspectives of vocalization, transmission, music and noise. As long as they meet the meaning of the question and the answer is not unique.
(2) Music affects Xiao Ming's father's reading. For Xiao Ming's father, music is noise at this time.
(3) Xiao Ming wears headphones when listening to music. This will not only let Xiao Ming enjoy music, but also let his father read without interference.
3. Omit 4. These three students reduce noise from three aspects: sound propagation mode, human ear and sounding object.
(1) The sound made by a tuning fork. Because the tuning fork vibrates regularly, it makes a pleasant sound; The vibration of the desk is messy and the sound is annoying.
(2) The analysis is reasonable. For example, the method to prevent the noise caused by dragging feet and stools requires students to correct their learning posture, overcome the bad habit of being active and prevent noise.
(3) (1) The noise mainly comes from the engine sound of passing vehicles, the peddler's hawking, the roar of machinery in factories or construction sites, the whistle of ships passing by on the Yangtze River, and so on.
Hazard: It will affect people's hearing, stimulate people's nerves and interfere with people's work. Long-term noise exceeding 150 dB will lead to the collapse of reinforced concrete buildings.
Measures include: banning motor vehicles from honking their horns in urban areas, banning flogging on holidays, and forcibly shutting down and scrapping old motor vehicles.
Implementation: it is good to ban singing and flogging; The scrapping of old vehicles needs to be strengthened.
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Eight Reference Answers in New Science Classroom
(3) according to the actual answer, reasonable.
1.2 inaudible sound
1, 1 .A 2。 B 3。 D 4。 D 5。 A
2, 1.√ 2.X 3。 X 4。 √ 5.X
3, 1.20 Hz ~20 000 Hz, height 2. Low 3. The sound made by butterfly wings is infrasound outside the range of human hearing 4. Infrasound is infrasound 5. Ultrasonic reflection inspection and processing. Ultrasonic reconnaissance detection Figure 4, omitted.
1.3 eyes and visible light
Lesson 65438
1, 1 .C 2。 C 3。 B 4。 D
2, 1. Intima content in adventitia 2. Photoreceptor of visual cell 3. Long curvature front concave lens
(l)① Pupil ② Cornea ③ Lens ④ Vitreous body Σ retina Σ choroid Σ optic nerve (2) Corneal lens vitreous lens retina optic nerve (3) in front of lens.
The eyeball wall is equivalent to the camera's black box, the cornea and lens are equivalent to the camera's lens, the pupil is equivalent to the camera's aperture, and the camera's negative film, the retina, is equivalent to the photosensitive film.
second kind
1、 1 . C2 . D3 . a4 . b5 . a6 . a7 . A8 . C9 . a 10 . d。
2, 1. Thick convex lens and thick concave lens 2. Focusing on both sides of the main optical axis focus 3. Concave and convex 4. Reversible focus 5. Convex-concave lens 6. Focus 7. Divergent concave is not necessarily 8. Virtual focus 3, omitted.
4, 1. Choose a magnifying glass and paper, put the magnifying glass in the sun, put the paper on the focus of the convex lens, and make a fire by using the condensing property of the convex lens.
2. Analysis: This problem can be distinguished from three angles: (1) the role of light (convex lens has a convergent effect on light, concave lens has a divergent effect on light); (2) From the aspect of appearance (the convex lens is thick in the middle and thin in the edge; The concave lens is thin in the middle and thick in the edge); (3) From the aspect of imaging characteristics (convex lens is inverted reduced image, inverted enlarged image, upright enlarged image, concave lens is not).
From the above three perspectives, there can be a variety of discrimination methods, and with the deepening of learning, more discrimination methods can be obtained.
Answer: Method 1: Point the lens directly at the sun and look for the smallest and brightest point from the other side of the lens. What you can find is a convex lens, otherwise it is a concave lens.
Method 2: Touch the lens surface by hand. The convex lens is thick in the middle and thin in the edge. The concave lens is thin in the middle and thick in the edge.
Method 3: Observe the words on the book with the lens. If you see the words in the book enlarged, this lens is convex, otherwise it is concave.
The third category
1， 1.d2.b3.b4.b5.b6.d7.d8.a。
2, 1. The photosensitive film of convex lens is inverted to restore the truth. 2. Less than 3 are far from it. Enlarge the convex lens vertically and enlarge the virtual image. 4. Enlarge the convex lens vertically. 6.7. 1 times the focal length and vertically enlarge the virtual image with the same focal length of 8. 1 times. 9. Small and small 10. Three photos in one photo, omitted.
4, 1. Hint: The concave lens becomes a vertically reduced virtual image. 2. The semi-circular glass at the bottom of the "Fairy Cup" is like a convex lens, and the photo is fixed on the base of the glass, so the distance between it and the convex lens is greater than the focal length of the lens, so it cannot form an enlarged virtual image. When the cup is full of wine, the focal length f' of the "combined convex lens" formed by the wine and the cup increases, which is greater than the distance between the photo and the lens.
1.4 invisible light
1, 1 .C 2。 C 3。 B 4。 B
2, 1: red, orange, yellow, green, blue, cyan, purple, 2. Strong rise, 3. Bacterial luminescence is good for health and harmful to sunlight, 4. High body temperature and strong infrared rays, 5. Sunlight, ozone layer, ozone layer, freon.
3, 1. Money detector (1) checks the authenticity of money, and ultraviolet rays make fluorescent substances sprayed on objects glow. (2) Bank checks money, etc. 2.( 1) Sunlight (2) Ozone layer in the upper atmosphere (3) Because the refrigerant in the refrigerator is Freon, when the refrigerator is damaged, the Freon inside will diffuse into the atmosphere. It poses a threat to the ecological environment of the earth. (4) In order to protect the living environment of human beings, 1987, the Montreal Protocol on Restricting the Production and Use of such Substances was signed worldwide, and now substitutes for freon have been developed, such as R 134a and cyclopentane. China signed the Montreal Protocol in 19 1.
Scientific quality assessment volume a
1、 1 . D2 . B3 . B4 . D5 . C6 . C7 . c8 . a9 . c 10 . c 1 1 . c 12 . c 13 . d 65438。
2, 1.× 2.x3.x4.x5.x6.√ 7.x8.√ 9。 √ 10.x。
3, 1. Loudness energy 2. Vibrating air 3. Slow and small 4. Ability 5. Transmission information noise 6. 134257. Convex deficiency 8. The larger nine. Enlarge the virtual image vertically by 5 10. Mechanical alarm clock b foam clothes foil paper 1 1. (65438 D concave lens is a 12. Help the human body to form vitamin D, kill microorganisms and make fluorescent substances glow. 13. Extend the focus ring forward.
14.2.7 cm (estimated 2. 5 cm ~ 2. 8 cm) vertical magnification 15.20 10 virtual image.
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Three new science classroom eight reference answers
5.l. The accumulated water is equivalent to a convex lens, which can concentrate sunlight, bake vegetables and even cause a fire.
2. People's gestures and the sound of patting the fish tank may scare the fish away, because goldfish can see fish not only from the air, but also from the water.
Light can also be heard from the fish tank into the water.
Experimental method: (1) Gesture in front of the fish tank, but make no sound, and observe whether the fish will be scared away. If so, it means that gesturing can scare the fish away;
(2) After wrapping half a fish tank with cloth, pat the fish tank through the cloth to see if the fish will be scared away. If it is, it means that the fish will be scared away by the sound.
3. Glasses can be placed slightly close to an object (such as words in a newspaper). If the image of the object is upright and magnified, the glasses are reading glasses. Because reading glasses are convex lenses, when an object (or text) is placed in its focal length, an upright magnified virtual image will appear. Concave lenses can only form upright and reduced virtual images of objects.
Scientific image quality evaluation volume b
1、 1 . B2 . D3 . C4 . C5 . C6 . D7 . b8 . d9 . a 10 . d 1 . c 12 . b 13 . d 65438。
2, 1.√ 2.√ 3.x 4。 √ 5.x 6。 √ 7.√ 8.x 9。 √ 10.x
(3) 1.( 1) Vibration (2) The greater the amplitude, 2. Thin back convex lens (3. F 4, 1) is related to the amplitude of the sound source. (2) The loudness of sound is getting smaller and smaller, indicating that the loudness of sound is also related to the distance from the sound source. (3) After the train passes, the sound becomes "dull" when it is far away. The suspected tone (frequency) is related to the speed and direction of sound source movement.
2. Turn on the TV and use the remote control to switch channels to determine whether the remote control works normally on the TV. Put a piece of paper on the straight path between the remote control and the TV to see if the remote control still works. Change the position of the paper and do it several times. According to the observed phenomenon, we can draw a conclusion that infrared rays propagate in a straight line in the air, and can also be remotely controlled in the direction of walls and floors, because walls and floors reflect infrared rays.
3. Hint: Generally, people's hearing frequency ranges from 20 Hz to 20 000 Hz, and sounds with frequencies below 20 Hz and above 20 000 Hz are imperceptible to most people.
4.( 1) Parallel light sources (candles, sunlight, etc. ), three lenses, optical bench (or ruler), light curtain (or white paper, etc. ).
(2) The main steps of inquiry:
(1) The glass convex lens is facing the sunlight, and the brightest spot is found behind the mirror with a light curtain;
② Measure the distance from the brightest spot to the convex lens with a scale, that is, the focal length FA;
③ Measure the focal lengths fb and fc of the crystalline convex lens and the plastic convex lens in the same way.
(3) experimental phenomena or experimental data record form:
Number of experiments
Focal length fa/cm of glass convex lens
Focal length fb/cm of crystal convex lens
Focal length fc /cm of plastic convex lens
1
2
three
(4) In this inquiry process, the main scientific research method is experiment (comparing and controlling variables).
5.( 1) Water convex lens light curtain (2) Place the candle, water convex lens and light curtain on the optical bench in the order shown in the figure, keep them at approximately the same height, and adjust the position of the water convex lens to make the candle form a clear image on the light curtain; Injecting water into the water convex lens makes the lens thicker, and the candle image formed on the observation screen will become unclear; Put the candle near the water convex lens, and a clear image will appear on the observation screen again.
2. Energy conversion in mechanical motion
2. 1 mechanical energy
Lesson 65438
1， 1.d2.c3.c4.a5.c6.a7.c。
2, 1 .× 2.√ 3.× 4.× 5.√ 6.√
Three, 1. Have the ability to do the work. Moving mass speed 3. Is elevated to a higher quality position 4. (1) kinetic energy (2) gravitational potential energy (3) motion (4) gravitational potential energy (5) kinetic energy and gravitational potential energy 5. (1) Increase (2) Decrease (3)
second kind
1， 1.b2.d3.c4.d5.c6.c。
2, 1. Elastic deformation, elastic deformation, mechanical deformation, 3. Decrease, increase, decrease, increase, gravity potential, 4. Shot put, 5. Gravity potential, dynamic elastic potential, dynamic gravity potential, 6. Dynamic gravity potential, 7. Heavy change, small change, big change, small 8 change, dynamic gravity potential machinery, 9. Small decrease and big increase.
Three, 1. In the process of children sliding down from the top of the slide, the gravitational potential energy is converted into kinetic energy, and the sliding speed of Institute 4 is increasing.
2. Pedal a few times before going uphill, and the speed of the bicycle will increase, thus increasing the kinetic energy. When going uphill, more kinetic energy will be converted into gravitational potential energy, which is convenient for rushing uphill.
3.( 1) The mechanical energy of water is converted into electrical energy. (2) location B. The reason is that the water drop at site B is larger than that at site A, so the potential energy of water can be used more. Or, the water at B is larger than that at A, so the water impacting the turbine has more kinetic energy.
2.2 Work and power
Lesson 65438
1, 1 .C 2。 C 3。 D 4。 C 5。 B 6。 A seven. C
2, 1.√ 2.√ 3.X 4。 √ 5.× 6.√ 7,× 8.√.
Three, 1. The force acting on an object is 2.3000J3.2000J04.50005.5002004,1.800J02. (1) 300N (2) 2400J.
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Eight Reference Answers in New Science Classroom
second kind
1, 1 .D 2。 B 3。 C 4 explosive D 5。 A
2, 1.× 2.× 3,√ 4 .X
Three, 1. How fast does an object do work? Watt 2. This machine can do work every second,150J3.100J25W4.501285.1:33:16.5000J20W7. Less than or greater than.
1(1) 375j (2)125w2.5x106w3.2m/s14700n14700n.
2.3 Simple machinery
Lesson 65438
1, 1 .A 2。 B 3。 C 4 explosive B
2, 1.√ 2.X 3。 X 4.×
Three, 1. Lever 2. Pivot the dynamic resistance power arm resistance arm 3. Finger chopsticks vegetable chopsticks 4. C B。
4. 0.8m from the front end (or 0.6m from the back end).
Fifth, it is necessary to change the arm of force and do more experiments to find out the laws that are generally followed when lever is balanced.
The third category
1, 1 .C 2。 B 3。 C 4 explosive B
2.1.4g2.5n3. It will be more labor-saving to reduce the resistance arm when the resistance and the force arm remain unchanged. 4. Wang Xiaogang's greatest strength arm is the radius of the wheel, and Wang's greatest strength arm is the diameter of the wheel. 5. the same.
Iv. 1 .660 N 825 N
Five, 1. Tie one end of one stick to the middle of another stick with a rope, and hang a bucket near the tie point of this stick at 1 3, as shown in the figure.
2. Experimental steps: 1. Find the midpoint of the thin stick with a scale. 2. Hang the hook code on one end B of the stick, and hang it on a point C in AB with a thin thread to balance the lever. 3. Measure the length of AC and BC. M = BC AC.M
Category 4
1, 1 .A 2。 D 3。 B 4。 D
Two, 1. Deform equal arms and change the direction of strength by force. The power arm is twice as large as the resistance arm. Try to change the direction of power II. 15 2 19 3.400N 200N 4。 500 5.5 108 6.250 7.55 5.
Fourth, because the crown block is not hard, the gravity of the fat man is greater than that of the bag, and the gravity of the bag is greater than that of the thin man, so the fat man can hold the bag, but the thin man can't.
2.4 mechanical efficiency
Lesson 65438
Scientific quality assessment volume a
1， 1D 2 B 3 B 4D 5 A 6 B 7 C 8 C 9D 10 A
2, 1. Dynamic gravity potential 2. = = pb > Pa 2。 Increase the pressure (1) The pressure of the same liquid at the same depth in all directions.
(2) The pressure of different liquids at the same depth is three, slightly.
Fourthly, the pressure of liquid increases with the increase of depth. In order to resist the strong pressure in deep water, the dam bottom should be designed to be wide at the bottom and narrow at the top. Lower the center of gravity, save materials, own pressure and stability.
Category 4
1, 1.B 2。 C 3。 A 4。 A 5。 B
2.l. great equality 2. 3.Pa < pb & ltPc pa iii。 L. The water in the cup exerts upward pressure on the plastic sheet; When the inner and outer water surfaces are almost the same, the plastic sheet sinks; At this time, the downward pressure of the water in the pipe on the plastic sheet is almost equal to the upward pressure of the water in the cup, and the pressure is offset, so the plastic sheet sinks due to its own gravity. 2.5. 15 × 105 Pa 3。 When the pipeline is erected, the water depth in the pipeline becomes larger, the pressure on the vegetable residue increases, and the vegetable residue is washed away under the pressure.
5. Punch holes around the coke bottle and fill it with water, which shows that the liquid pressure is all-round; Drilling several holes at the same height and filling them with water can show that the pressure of liquid is equal in all directions at the same depth; Perforation and water filling at different depths show that the deeper the place, the greater the liquid pressure.
The fifth category
1, 1.B 2。 D 3。 D 4。 B 5。 B
2, 1. Vertical pressure 2. The buoyancy of an object immersed in a liquid is equal to the gravity of the liquid it displaces; G row =m row g=P liquid v row g gas 3.54.0.01200010001010.
5. Stay the same and grow bigger
3, 1. Analysis: This question is an inquiry question, based on Archimedes' principle: F float = P liquid g V row. Buoyancy is only related to the density of liquid and the volume of liquid displaced by the object. The buoyancy of the object in the topic can be calculated by weighing method, because buoyancy is related to two factors at the same time, so we should use the control variable method to keep one of the factors unchanged before exploring.
Answer (1): The relationship between buoyancy and the volume of liquid displaced by the object 12③ or 12④ In the same liquid, the greater the volume of liquid displaced by the object, the greater the buoyancy.
Answer (2): Relationship between buoyancy and liquid density 135 145 When the same object is immersed in different liquids, the greater the liquid density, the greater the buoyancy.
Answer (3): The relationship between buoyancy and the immersion depth of an object in liquid.
2.( 1)6.75 1.50 (2) When an object is not completely submerged, the deeper it invades, the greater its buoyancy (3) After it is completely submerged, its buoyancy is independent of its depth (4 )B
The sixth category
1， 1.b2.d3.b4.a5.a6.c。
2, 1. Buoyancy and gravity 2. Bigger than the same 3. More water is hollow.
Ship number four. Quality of ship cargo. Tips for changing your own gravity: There are symmetrical water tanks on both sides of the submarine. When the water tank is filled with water, the submarine gradually becomes heavier and gradually dives into the water; When part of the water in the water tank is discharged by compressed air, the gravity decreases and the submarine floats. Therefore, the submarine changes its own gravity to dive and float through water intake and drainage. 6. Reduce the buoyancy. 7. Buoyancy is less than volume Tip: After the balloon is inflated, the balloon becomes bigger. According to Archimedes' principle, F float =p air g V, the buoyancy of the air received by the balloon will increase. When it deflates, the volume of the balloon will decrease. Buoyancy decreases. It can be seen that the purpose of changing the balloon volume is to change the buoyancy of the balloon, so as to achieve the purpose of free lifting. 8.4× 108 4× 108 3.88× 108.
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Eight Reference Answers in New Science Classroom
3, 1.( 1) Sinking (2) Suspending (3) Floating Direction: According to Archimedes' principle and the floating and sinking conditions of objects, we can deduce a method to judge the floating and sinking of objects according to the densities of liquids and objects:
(1) When P solution >: P object, the object will float;
(2) When pLiquid = pObject, the object will be suspended;
(3) When liquid P is substance G, the line segment of buoyancy is drawn slightly longer,11×1071071×10365438.
16.( 1) stress zone pressure (2) increases the stress zone and reduces the pressure (3) sharpens the staple mouth, reduces the stress zone and increases the pressure (17). (1) conforms to the objective facts; (2) obeys the law of conservation of mass (18).
3, 1.( 1) Question: Why do eggs float? Guess: the buoyancy of eggs is greater than gravity (or: what is the relationship between buoyancy and liquid density; Conjecture: liquid has high density and high buoyancy) (2) In gas, the higher the speed, the lower the pressure. 2.( 1) The greater the pressure (obviously) (2) It is related to the stress area. (3) On the basis of the picture on the right, keep the water in the bottle unchanged, invert the bottle on the sponge, and observe the sinking degree of the sponge. Compared with the original effect. 3.( 1) density depth (2) depth liquid (in water and salt water) (3) A 4. Solution: Let the side length of small cardboard be a, the mass of a 1 yuan coin be m, the pressure of small cardboard on the bag: Pl, and the pressure of large cardboard on the bag: P2, because Pl >；; P2, so lift the cardboard first. Among them
5.( 1) The gravity of boiling water discharged by the ball is the buoyancy of the ball:
(2) Because the buoyancy is greater than the gravity of the ball, the ball moves upward. When the ball began to surface, the gravity of the discharged water gradually decreased. When the buoyancy is equal to the gravity of the ball, that is, when the buoyancy is equal to 4N, the two forces are balanced and the ball is at rest.
6.( 1) all conform to (2) because only 4Go2 participated in the reaction. 7.( 1) Carbon, H2, Iron and Cobalt
Scientific quality assessment volume b
1、 1 . C2 . a3 . a4 . b5 . B6 . B7 . c8 . B9 . a 10 . d 1 1 . c 12 . b 13 . c。
14.C 15。 A 16。 B 17。 B 18。 D 19。 C 20。 B 2 1。 D 22，A 23。 C
2.1.3×1081.1.2. The stress area decreases with the increase of depth. 3. Atmospheric pressure enters the flask. 4. The middle is small and the middle is big. 5. salt 6. (1) The measured object is subjected to the buoyancy of water (or alcohol) A and C (or D) (2). Explore the relationship between buoyancy and liquid densities d and e 7. Saturated salt water is denser than water, and strong alcohol is pressed at the same depth. 8. The density of natural gas is smaller than that of air, and the leaked natural gas will rise. Only when an alarm is installed on it can the alarm be given in time. 9. Wind accelerates the evaporation of alcohol on the windward side of fingers; Evaporation absorbs heat, which reduces the temperature of the windward side and makes it feel cooler. The newly fished eggs will not be too hot, because the water on the surface of the eggshell evaporates and absorbs heat. The water on the eggshell is dry, the temperature of the egg is still very high, and the fire reaches the hand, and it feels hot 1 1. Ventilation in sunny places has fast air flow, high temperature and fast evaporation 12. Water droplets rise and liquefy to release heat 13. C.
14. The tea leaked from the micropores absorbs heat by evaporation, which reduces the temperature in the pot.
19.①②④
Second, 1. (1) range index value (2) cardboard with holes in the center prevents heat loss and shortens the time from heating to boiling of water (3) Answer 1: If there is too much water, pour out some water. Answer 2: The initial temperature of water is too low. Do experiments with hot water. Answer 3: Use the inner flame of alcohol lamp and heat it with the outer flame. (4) Hear a loud noise or see "white gas" on the water surface before boiling. (5)98℃ remains unchanged. (6) omitted 2. (1) Once the safety valve of the pressure cooker fails, the gas pressure in the cooker is too high and the temperature will also rise. When the temperature reaches the melting point of the fusible piece, heating is continued, the fusible piece begins to melt, and the gas in the pot is ejected from the vent hole, thus reducing the pressure in the pot, thus preventing the occurrence of explosion accidents. (3) 1 150C If this pressure cooker is to be sold in Tibet, the quality of the safety valve should be appropriately improved.
3.( 1)30N(2)30O N 3× 103 Pa
Mid-term scientific quality assessment
1、 1 . C2 . D3 . B4 . C5 . D6 . B7 . c8 . d9 . c 10 . d 1 1 . c 12 . a 13 . d。
14.A 15。 C 16。 B 17。 A 18。 D 19。 C 20。 B
2, 1. Tone loudness 2. Convex and concave 3. Camera combination convex lens (lens) film deformation 4. Thermobiological effect is 5.7×1036.1n1×10-4m3 7.3258.500 400 80%.
4. L. Hint: Measure the focal lengths of the three lenses by the sun focusing method respectively, and then make a judgment. 2. First, measure the gravity G of the stone in the air with a spring dynamometer; Then the gravity g' of the stone in the water is measured by a spring dynamometer; Finally, calculate the density of the stone, p=Gp water /G-G' 3. Equality or inequality. The hydrogen produced by the reaction between zinc and dilute sulfuric acid designed by Xiaohua Xiaoming escapes into the air.
Five, 1. (1) magnifying glass, "presbyopia" lens, projector lens (or slide projector lens) (2) crystal, resin (3) object distance is greater than.
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6 "New Science Classroom" Eight Reference Answers
4 mobile charge
4. 1 cognitive circuit
1, 1 .A 2。 B 3。 D 2， 1。 Electrical switch of power supply 2. Open and close.
Three, 1. The mistake is to mix the physical diagram with the circuit diagram symbols. Switches are physical diagrams, and circuits and bells are symbols of circuit diagrams. Both a and b are wrong. A is wrong because there is no power supply and the switch connected to B will be short-circuited.
4.2 Current
Lesson 65438
1, 1 .A 2。 D 3。 C 4 explosive B 5。 C
Directional motion of 2, 1. charge 2. Positive and negative chemical electricity 3. Plus or minus 4. External power supply from b to a b.
second kind
1， 1.d 2.a，c 3.a，c，d 4.a 5.a，c。
2.1.0 ~ 0.6a0.24a0 ~ 3a0.8a2. (1) Series (2) Positive and negative (3) Range estimation test (4) Electrical apparatus 3. (1) The current exceeds the range used by the ammeter. (2) Connect the 0 ~ 3a range of the ammeter.
4. The "+"one "range of parallel voltage is 5.8.5 V1.7v6. The"+"and" one "terminals of the voltmeter are connected reversely. Switch the leads from the "+"and "one" terminals of the voltmeter and reconnect the 7.0~3 high 0. 1 V 8. L2 one and.
The third category
1, 1 .A 2。 A 3。 A 4。 C 5。 D
2. 1.2 2. The deflection amplitude of ammeter pointer is too small; Connect the wire connected to "3" to "0.6". 3. Zero scale adjustment spiral zero scale 4 .. (1) L2 (2)1.5 (3) b "-"
4. 1. (1) The currents in all parts of the series circuit are equal. (2) The main loop current in parallel circuit is equal to the sum of all branch currents. 2. Answer: The positive and negative poles of the ammeter are connected backwards. B: The choice of ammeter is too wide. C: The selection range of ammeter is too small.
Category 4
1, 1 .A 2。 C 3。 A 4。 D
2, 1. Parallel 2 .3 1.5 3. Current, voltage and current 4. The incorrect fault is that the current flows in from the "one" terminal of the voltmeter and flows out from the "+"terminal 5. Voltage, current and current 6. (1) voltmeter should not be connected in series in L2 branch, but should be connected in parallel at both ends of L2 (2).
4. 1. (1) Series (2) The currents in the series circuit are equal (3) The total voltage across the series circuit is equal to the sum of the voltages across each part of the circuit.
2.
Between BC
close
If there is reading, L2 is on, then L 1 is on.
Between BC
close
Without reading, L2 is turned on, and L 1 is short-circuited.
Between BC
separate
If there is a reading and L2 is on, L 1 is short-circuited.
4.3 resistance
Lesson 65438
1， 1.b2.a3.c4.d5.c6.b7.b。
2, 1. The barrier conductor is not easy to conduct electricity. 2. Conductive leakage and electric shock. 3. Leakage or electric shock. 4. The degree of obstruction. 5.R ohm ω increases. 6. Superconductor semiconductor. 7. When the material and length are the same, the larger the cross-sectional area of the conductor, the smaller the resistance. Control resistance wires with the same length, the same cross-sectional area and different materials by variable method.
(1)a c (2) When the conductor material and cross-sectional area are the same, the longer the conductor, the greater the resistance (the conductor resistance is proportional to the length, etc. (3) Study the relationship between current and voltage and resistance, the relationship between pressure and stress area, and the relationship between kinetic energy of an object and mass and speed (as long as it is reasonable) (4)① Method: wick the waste light bulb and power supply with wires. The ammeter is connected to the circuit shown in the following figure (a), and then the wick is heated with an alcohol lamp. At the same time, observe and analyze the change of current characterization, and discuss the conclusion. (2) The circuit diagram is shown in the following figure (b) (no physical drawing is required).
second kind
1， 1.d2.a3.d4.b5.b6.c7.b。
2, 1. Length current 2. Long, big, small and dark 3. Sliding rheostat resistor 4. Maximum resistance100Ω. The maximum allowable current is 2A5.02040606 Voltage, current and voltage.
1~2. Slightly four, 1. (1) as shown in the figure.
(2)① disconnect a, ② turn on the light bulb, ③ short the light bulb, 2. There are no appliances in the circuit; After the switch is turned on, if the sliding vane of the sliding rheostat is improperly positioned, it will burn out the ammeter and damage the power supply.
4.4 Relationship among Current, Voltage and Resistance
Lesson 65438
1， 1.d2.b3.b4.ac5.a6.b。
2. The resistance of the1.conductor must be 2. The inverse ratio is 3.6a4.6 1. 105. Inverse ratio.
6 .3 200 7. 18Ω
Thirdly, it can't, because there are four current indicators, and the resistance value of the constant resistor is connected to 9V1.125a2.0.75a3.1.33a.
Five, 1. (1) Series power supply (2) The currents in the series circuit are equal (3) The total voltage of the series circuit is equal to the sum of the voltages of all series parts (4) When the resistance is constant, the current is proportional to the voltage (5)10Ω15Ω (6) A65438+.
second kind
1， 1.d2.a3.d4.b5.c6.d。