1. Rice cookers, electric woks and electric kettles all use electric energy to convert into internal energy, and all use heat transfer to cook, cook and boil water.

2. The exhaust fan (range hood) converts electric energy into mechanical energy, and air is converted by air convection.

3. Insert the three-pin plug of the rice cooker, electric frying pan and electric kettle into three hole socket to prevent electric leakage and electric shock.

4. The microwave oven has the advantages of uniform heating, high thermal efficiency and no pollution. The heating principle is to convert electric energy into electromagnetic energy, and then convert electromagnetic energy into internal energy.

The electric light in the kitchen works by converting electric energy into internal energy and light energy by the thermal effect of current.

6. Kitchen stoves (honeycomb coal stoves, liquefied gas stoves, coal stoves and wood stoves) convert chemical energy into internal energy, that is, fuel burns to release heat.

Second, phenomena related to mechanical knowledge.

1, the spout and belly of the electric kettle form a communication device, and the water surface is always flat.

2. The thin edge of the kitchen knife is to reduce the stress area and increase the pressure.

3, the blade of the kitchen knife has oil, in order to cut vegetables when the contact surface is smooth, reduce friction.

4. The handle, spatula handle and electric kettle handle have convex and concave patterns, which make the contact surface rough and increase friction.

5, fire shovel to send coal, is to use the inertia of coal to send coal into the furnace.

6. Pour boiling water into the thermos bottle and know the water level according to the sound. Due to the increase of water volume, the length of air column decreases, the vibration frequency increases and the tone increases.

7. Keep watering when grinding the kitchen knife, because the heat generated by the friction between the kitchen knife and the stone increases the internal energy of the knife, the temperature rises, the hardness of the knife edge becomes smaller, and the knife edge is unfavorable; Watering is to use heat transfer to reduce the internal energy and temperature of the kitchen knife without rising too high.

Third, phenomena related to thermal knowledge.

(a) Phenomena related to thermal expansion and heat transfer.

1, use the stove to boil water or stir fry, and let the bottom of the pot be placed on the outer flame of the flame, and don't let the bottom of the pot press the burner, because the temperature of the outer flame of the flame is high, which can make the temperature of the pot rise rapidly.

2, spatula, spoon, colander, aluminum pot and other cookware handles are made of wood, because wood is a poor conductor of heat, so it will not heat up during cooking.

3. The purpose of installing an exhaust fan above the cooker is to speed up air convection, so that kitchen fumes can be discharged in time to avoid polluting the space.

4. The hot casserole is easy to break on the wetland. This is because casserole is a bad conductor of heat. When the casserole is placed on the wetland, the outer wall of the casserole shrinks quickly, and the temperature of the inner wall drops slowly. The casserole shrinks unevenly inside and outside and is easy to break.

5. When the thermos bottle is filled with boiling water, it can be better insulated without it. Because there is a layer of air in the bottle mouth when it is not filled, it is a bad conductor of heat, which can better prevent heat loss.

6. Cooking mainly uses heat conduction to transfer heat, while cooking and boiling water mainly use convection to transfer heat.

7. Pour some boiling water from the thermos in winter. When you cover the cork tightly, you often see the cork jump up at once. This is because when boiling water is poured out, some cold air enters, and after the cork is plugged, the cold air enters expands rapidly when heated, and the pressure increases, thus pushing the cork away.

8. For the hot soup that just comes out of the pot in winter, it seems that the soup is not hot, but it tastes very hot because there is a layer of oil on the noodle soup that prevents the heat loss (water evaporation) in the soup.

9. In winter or when the temperature is very low, pour boiling water into the glass, and preheat the glass with a small amount of boiling water first, so as to avoid the excessive temperature difference between the inside and outside of the glass, and the thermal expansion of the inner wall is hindered by the outer wall, resulting in the glass breaking.

10. Boiled and scalded eggs are easy to shell when soaked in cold water for a while. Because hot eggshells and protein contract when they are cold, the degree of contraction is different, so they are separated.

(2) phenomena related to the state change of objects

1. Liquefied gas is compressed and liquefied at room temperature, and then put into a steel tank; When in use, liquefied gas is decompressed by the pressure reducing valve, changed from liquid to gas, and then enters the stove for combustion.

2. Boil water in a soldering iron pan, and the pot won't burn out. If you don't fill it with water, put it on the fire for a while and it will burn out. This is because at standard atmospheric pressure 1, the boiling point of water is 100℃ and the melting point of tin is 232℃. When boiled with water, as long as the water is not dry, the temperature of the pot will not obviously exceed 100℃, and it will not reach the melting points of tin and iron, so the pot will not burn out. If water is not put on the fire, the temperature of the pot will reach the melting point of tin in a short time, the solder will melt and the pot will burn out.

3. When boiling water or cooking food, the sprayed steam burns more seriously than hot water or hot soup. Because when steam turns into hot water or soup with the same temperature, it will release a lot of heat (liquefaction heat).

4. Cook food in a casserole. After the food is cooked, let the casserole leave the stove, and the food will continue to cook in the pot for a while. This is because when the casserole is out of the oven, the temperature at the bottom of the casserole is higher than 100℃, while the food in the pot is 100℃. After leaving the furnace, the food in the pot can absorb heat from the bottom of the pot and continue to boil until the bottom temperature drops to 100℃.

Cooking food in pressure cooker will be faster. Mainly to improve the air pressure in the pot and the boiling point of water, that is, to improve the temperature of cooking food.

6. In summer, a lot of "sweating" on the wall of the tap water pipe is often a sign of rain. The "sweating" of water pipes is not the water leakage in the pipes, but the water pipes are mostly buried underground and the water temperature is low. When the water vapor in the air contacts the water pipe, it will release heat, liquefy into small water droplets and attach to the outer wall. If there is a lot of "sweating" on the pipe wall, it means that the water vapor content in the air is high and the humidity is high, which is a precursor to rain.

7. Cooking food is not as fast as it gets hotter. Because the temperature of water remains unchanged after boiling, even if the firepower is increased, the water temperature cannot be raised. As a result, it can only accelerate the evaporation of water, make the water in the pot evaporate and waste fuel. The correct way is to boil the water in the pot with a big fire, and then keep the water boiling with a small fire.

8. After the water in the kettle is boiled in winter, you can see the "white gas" at a certain distance from the spout, but you can't see the "white gas" near the spout. This is because the temperature near the spout is high, and the water vapor from the spout cannot be liquefied, but the temperature at a certain distance from the spout is low; The water vapor ejected from the spout gives off heat and liquefies into small water droplets, that is, "white gas".

9. When frying food, splashing water droplets will hear the sound of "beep, beep" and spill oil. This is because the boiling point of water is lower than that of oil and the density of water is higher than that of oil. The water droplets splashed in the oil sink to the bottom of the oil and quickly heat up and boil, and the bubbles generated rise to the oil surface and make a noise.

10. When the temperature of the pot is high, sprinkling some water into the pot will make a "cheep, cheep" sound and release a lot of "white gas". This is because water evaporates quickly, then liquefies and makes a "cheep, cheep" sound.

1 1. When the soup boils and overflows the pot, quickly add cold water to the pot or scoop up the soup, which can reduce the temperature of the soup to below the boiling point. Add cold water. The temperature of cold water is lower than that of boiled soup. After mixing, cold water absorbs heat and soup releases heat. In the process of raising soup, because the air is lower than the temperature of soup, the soup releases heat and the temperature decreases. After pouring into the pot, it absorbs heat from the boiling soup, reducing the temperature of the soup in the pot.

(3) phenomena related to molecular thermal motion in thermodynamics

1. Pickled vegetables often take half a month to become salty, while salt is added for a few minutes when cooking. This is because the higher the temperature, the faster the ion movement of salt.

2. If you scrape a thin layer from the wall in the corner of the coal pile for a long time, you can see that it is black inside. This is because molecules move irregularly endlessly. In the corner where coal molecules have spread into the wall for a long time, you can still see that it is black after scraping off a layer.

In daily life and production, we can improve our ability to observe, analyze and solve physical problems by carefully observing the physical phenomena around us and connecting with the physical knowledge we have learned.

In the kitchen, if we pay attention to cookers, utensils and some phenomena in cooking and frying, we will find that many places need to use physical knowledge.

1. When porridge or rice is hot or cold, the pot makes a beep, beep, and bubbles keep popping up, but once it is tasted, porridge or rice is not hot. Why?

Heating cold porridge or rice is different from boiling water. Although water is a bad body of heat, its conduction speed to heat is very slow, but its fluidity is very good. The water at the bottom of the pot will expand when heated, float when the density becomes smaller, and the surrounding cold water will flow over to fill it. Through this convection, the heat at the bottom of the pot will be continuously transferred to all parts of the water, making the water hot. Cold porridge or cold rice has poor fluidity and is not easy to conduct heat. Therefore, when the porridge or rice at the bottom of the pot absorbs heat, the temperature rises rapidly, but it cannot flow up or around quickly. A lot of heat is concentrated at the bottom of the pot, and the porridge at the bottom of the pot is burnt. Because the heat is difficult to transfer to the porridge, the porridge on it is still cold. When heating cold porridge or rice, add more water to the pot to make porridge thinner and enhance liquidity. In addition, it is necessary to stir frequently and force convection, so that porridge can be heated evenly.

Secondly, when using casserole to cook the meat or cook soup, when the soup is boiled and removed from the stove, the soup will continue to boil for a while, but this phenomenon does not exist in wok and aluminum pot. Why?

Because the casserole is made of clay, and the specific heat of nonmetal is much larger than that of metal, and its heat transfer ability is much worse than that of metal. When the casserole is heated on the stove, the outer temperature of the pot is much higher than 100℃, and the inner temperature is slightly higher than 100℃. At this point, the pot absorbs a lot of heat and stores a lot of heat energy. After the casserole is taken out of the oven, the outer layer of the pot which is much higher than 100℃ will continue to transfer heat to the inner layer, so that the soup in the pot can still reach 100℃ and continue to boil for a period of time, so that the iron aluminum pot will not appear this phenomenon (please analyze the reasons yourself).

Third, the "cooked" in fried meat. On holidays, some people always fry a few meat dishes, so how to fry the meat slices?

If the meat slices are directly put into a hot oil pan and stir-fried, the water contained in the lean fiber will quickly evaporate, making the meat slices dry and hard, and even frying the meat, greatly losing its flavor. In order to stir-fry the sliced meat delicious, chefs often mix the sliced meat with a proper amount of starch in advance. After the meat slices were put into the hot oil pan, the water in the starch paste attached to the meat slices evaporated, but it was difficult to evaporate the water in the meat slices, which still kept the freshness of the raw meat and reduced the loss of nutrition. The meat is almost cooked, which means "cooked as soon as we meet" The sliced meat fried in this way is fresh, tender, delicious and nutritious.

4. What is the best way to thaw frozen meat? Take out the frozen meat and chicken from the refrigerator, how to thaw it?

It is best to use cold water close to 0℃. Because the temperature of frozen meat is below 0℃, if it is thawed in hot water, the frozen meat absorbs heat from hot water, and its outer layer is thawed quickly, so that the temperature rises to above 0℃ rapidly. There is a gap between the meat layers, which reduces the heat transfer ability, making it difficult for the frozen meat inside to absorb heat and thaw, forming a hard core. If frozen meat is put into cold water, the temperature of cold water will drop to 0℃ because of the heat absorption of frozen meat and frozen chicken, and some water will freeze. Because 1g water can release 80 calories when it is frozen (while 1g water can only release 1 calorie when it is lowered to 1℃), after frozen meat absorbs so much heat, the temperature of the outer layer of the meat rises rapidly, while the inner layer is easy to absorb heat, so the temperature of the whole meat also rises rapidly to 0℃. Repeat this several times and the frozen meat can be thawed. From the point of view of nutrition, this method of uniform and slow heating is also scientific.

Physical knowledge in automobiles

First, the mechanical aspect.

1, the mass of the automobile chassis is large, which can reduce the center of gravity of the automobile and increase the stability of the automobile when driving.

2. In order to reduce the resistance when the car is running, the body is designed to be streamlined.

3. The driving force of the car-the friction between the ground and the driving wheel (the friction between the driving wheel and the driven wheel is opposite to the ground).

4. When the car is driving at a uniform speed on a flat road-traction and resistance are balanced with each other, and the gravity borne by the car is balanced with the supporting force of the ground.

5. When the car turns: ① the driver should hit the steering wheel-force is the reason to change the motion state of the object; (2) Passengers will fall in the opposite direction of the curve-because passengers have inertia.

6. When the car suddenly brakes (decelerates), ① the driver's braking force is the reason for changing the motion state of the object; ② Passengers will dump in the direction of the garage-inertia; (3) The driver can stop with the principle of less force-lever; ④ Hard braking-increasing pressure and increasing friction; ⑤ When braking suddenly, the friction between the wheel and the ground changes from rolling friction to sliding friction.

7. There are still differences in the size and number of wheels for different purposes-this is related to the pressure on the road.

8. Car seats are designed to be wide and big, which reduces the pressure on passengers and makes them comfortable to ride.

9. When the car is driving at high speed, a low-pressure area will be formed at the rear of the car, which is why we can often see the curled dust at the rear of the car.

10, the traffic control department requires: ① drivers and front passengers must fasten their seat belts-this can prevent the harm of inertia; (2) It is forbidden to overload vehicles-it is necessary to reduce the damage of vehicles to the road surface and reduce friction and inertia; (3) Prohibit vehicles from speeding-to prevent accidents caused by too long reaction distance and braking distance during sudden braking.

1 1. Application of simple machinery: ① steering wheel, wheels, window handles, etc. They are all axles; ② The speed control lever and the automatic door switch device are levers.

12, when climbing, the car should be adjusted to low speed: from P=Fv, under the condition of constant power, reducing the speed can increase the traction.

13, about the calculation of speed, distance and time; Description of reference object and motion state

14, know the signs such as speed limit, mileage and no singing, and understand their meanings.

Second, acoustics.

1, the car horn should be loud, and the sound of the engine should be eliminated as far as possible (muffler is installed on the engine)-this is to reduce the noise at the sound source.

2. In order to reduce the impact of noise from vehicles on roadside residents, set up barriers or plant trees along the roadside-noise can be reduced during transmission.

3. Speaker sound: electric energy-mechanical energy

Third, heat dissipation.

1, automobile engines often use diesel engines or gasoline engines-they are internal combustion engines-to use internal energy to do work.

2. The engine is equipped with a water jacket, which uses circulating water to help the engine dissipate heat-water has a large specific heat capacity.

In order to prevent the water tank from freezing in winter, the water in the water tank should be drained at night-to prevent the danger of thermal expansion and cold contraction.

A series of heating wires are embedded in the glass plate of the rear window of the car-it can prevent the fog formed in the car from adhering to the glass and condensing.

When you just get on the bus or a car passes by you, you will smell the strong smell of gasoline-diffusion phenomenon.

6. The air-conditioned car window glass is designed to be double-layered to prevent heat transfer.

7. The use of gas fuel in environment-friendly cars can reduce the pollution to the atmosphere.

Fourth, electrical aspects.

1, the engine of an automobile is usually started by a low-voltage motor: the motor is made according to the effect of magnetic field on current, and it converts electric energy into mechanical energy when working.

2. Automobile motors are usually powered by on-board batteries, and wheels can be used to drive the on-board generators to generate electricity and charge the batteries. When charging the battery, the electric energy is converted into chemical energy and stored, and the battery is an electrical appliance at this time; When the battery is used to supply power to the motor, chemical energy is converted into electrical energy, and the battery is the power supply at this time.

3. Car batteries are also used to supply power for air conditioners, fans, tape recorders, CD players and lamps of various purposes, which can be easily converted into mechanical energy, acoustic energy and light energy.

3. Generally, an iron chain is hung at the tail of the tanker to reach the road surface, which is beneficial to make the charge generated by bumps spread to the earth quickly during transportation and avoid the disaster caused by electrostatic discharge.

4, the lights are shining: electric energy-light energy

Verb (abbreviation for verb) optical aspect

1. The rearview mirror beside the car and the observation mirror at the intersection are convex mirrors, which can broaden the field of vision.

2. When the car is driving at night, the lights are generally not turned on in the car, which will hinder the passengers in the car from imaging on the windshield in front of the driver and interfere with the driver's correct judgment.

3. The windshield in front of the car is usually not upright (except for cars with high chassis). This is because the windshield is equivalent to a flat mirror, and the objects in the car can easily be imaged in front of the driver through it, which affects the driver's judgment.

4. Automobile taillight lampshade: The corner reflector can reflect the incoming light to ensure the safety of the vehicles behind.

5. car headlights: concave mirror reflection principle, the short-distance filament is near the focus, and the long-distance filament is at the focus.

Physical knowledge on bicycles

Do you know what physical knowledge there is on the bike? Let's have a look.

1. Friction knowledge on bicycles.

① Why do bicycle tires have uneven patterns?

Friction is related to two factors: pressure and roughness of contact surface. The greater the pressure, the greater the friction; The rougher the contact surface, the greater the friction. Bicycle tires have uneven patterns. By increasing the roughness between the bicycle and the ground, the friction is increased, and the purpose is to prevent the bicycle from slipping.

② Why can bicycles go forward?

When we ride a bicycle, because people and bicycles have pressure on the ground, the tires are not smooth, and there is friction between the bicycle and the road. However, why can bicycles move forward? This is also caused by the friction between the rear wheel and the ground, and the direction of this friction is forward. What is the friction of the front wheel? Hinder the movement of the car! Its direction is opposite to that of the bicycle. It is these two forces that are equal in magnitude and opposite in direction, so the bicycle moves at a constant speed. When a person pushes a bicycle forward on the ground, the friction direction of the front and rear wheels is backward. Then who is balancing these two forces? The friction between the foot and the ground is forward!

③ Why can a bicycle stop after braking?

When braking, the friction between the brake shoe and the rim will hinder the rotation of the rear wheel. The greater the hand pressure, the greater the pressure of the brake shoe on the rim, the greater the friction generated, and the slower the rotation of the rear wheel. If you stop completely, the friction between the rear wheel and the ground becomes sliding friction (originally rolling friction, the direction is forward), and the direction is backward, which hinders the movement of the bicycle, so you stop.

(4) Where are the steel balls installed on the bicycle? Why Zhu Gang?

There are steel balls in the front axle, middle axle, rear axle, handlebar rotation and pedal rotation of bicycles.

People always want to ride bicycles easily, flexibly and with less effort. Rolling instead of sliding can greatly reduce friction. Therefore, in order to install steel balls where the bicycle rotates, we can often add lubricating oil to keep the contact surfaces away from each other, which can reduce the friction.

2. Knowledge of lever and axle of bicycle.

(1) lever on bicycle

A. Lever to control the steering of the front wheel: The handlebar of a bicycle is a labor-saving lever. People can turn the front wheel of a bicycle with little force to control the direction and balance of the bicycle.

B. Lever to control the brake: The brake handle on the handlebar is a labor-saving lever, so people can press the brake on the rim with little force, and the pressure is great.

② Axles on bicycles.

A. Pedal and thumbwheel on the central shaft: form a labor-saving wheel shaft (the pedal radius is greater than the thumbwheel radius).

B, bicycle handlebar and front fork axle: form a labor-saving axle (the turning radius of handlebar is greater than the radius of front fork axle).

C. Gears on the rear axle and rear wheel: constitute a laborious axle (the gear radius is smaller than the rear wheel radius).

3. Knowledge of bicycle air pressure.

Inflating the inner tube of bicycle: All kinds of early wheels were wooden wheels and iron wheels, which were uneven. Modern bicycles use inflatable inner tubes mainly to increase the pressure in the fetus, which can play a buffering role and reduce the resistance of bicycles.

Function of valve core: The valve core on the inflatable tube acts as a one-way valve, allowing only gas to enter, preventing gas from leaking out, facilitating air intake and ensuring the tightness of the inflatable tube.

4. Optical knowledge on bicycles.

The red taillight on a bicycle can't glow by itself, but it can remind the driver at night, because the taillight of a bicycle is composed of many honeycomb-shaped "cells", and each "cell" is composed of three reflective surfaces with an angle of about 90 degrees. In this way, at night, when the light of the car behind hits the taillight of the bicycle, it will produce reflected light, which can attract the driver's attention because of its striking red color.

Bicycle is a very popular means of transportation in China. A lot of mechanical knowledge is applied to its "body"

Application of 1. measurement

When measuring the length of the runway, you can use a bicycle. For example, the diameter of an ordinary wheel is 0.7 1 m or 0.66 m. Then the length of a circle is the diameter times π, which is about 2.23 meters or 2.07 meters. Then, let the car roll along the runway, record the number of laps n, and the length of the runway is n×2.23 meters or n×2.07 meters.

2. Application of force and motion

(1) Reduce and increase friction.

The front axle, intermediate axle and rear axle of a car are all rolling to reduce friction. In order to further reduce friction, people often add lubricants to these parts.

Many places are engraved with uneven patterns to increase friction. Such as tires, plastic handle covers, pedal covers, brake handle covers, etc. Changing rolling friction into sliding friction to increase friction. For example, when braking, the wheels stop rolling, but slide on the ground, and the friction is greatly increased, so that the car can stop quickly. At the same time of braking, hold the brake handle by hand to increase the pressure of the brake shoe on the steel ring, so that the wheel stops rolling.

(2) The damping effect of the spring.

There are many springs under the car seat cushion to absorb shock.

3. Application of stress knowledge

(1) Bicycle tires are engraved with loads. If the vehicle is too heavy, the tires will be crushed due to excessive pressure.

(2) The seat cushion is saddle-shaped, which can increase the contact area between the seat cushion and the human body to reduce the pressure on the buttocks, so that people are not easy to feel tired when riding a bicycle.

4. The application of simple mechanical knowledge

The brake handle and connecting rod in the bicycle brake system are labor-saving levers, which can increase the tension on the brake pad. In order to save labor or distance, bicycles also use axles: pedal plates and sprocket plates; Rear wheel and flywheel, faucet and rotating shaft, etc. 5. Knowledge application of work and mechanical energy

(1) According to the principle of work, distance is needed to save labor. So when people go uphill, they often ride the "S-shaped" route, which is the reason.

(2) The mutual transformation between kinetic energy and gravitational potential energy.

For example, before riding uphill, people often have to pedal a few times, which makes it easier to get up. Here, kinetic energy is converted into potential energy. And riding downhill without pedaling, the speed is getting faster and faster, which is the conversion of potential energy into kinetic energy.

6. Application of the Law of Inertia

If the front wheel of a fast bicycle suddenly stops, why does the rear wheel jump? This is because the front wheel suddenly stopped moving because of resistance, while the people and the rear wheel in the car did not. According to the law of inertia, people and the rear wheel should keep moving forward, so the rear wheel will jump.

Remember not to use the bicycle front brake alone when driving downhill or at high speed, otherwise a rollover accident will occur!