2011 Jilin Province Changchun City High School Physics Examination Syllabus

Summary of knowledge points for the Physics Examination

1. Mass point

The point with mass used to replace an object is called a mass point. This is an idealized model proposed for studying object motion.

When the shape and size of the object have no or little impact on the research problem, the object can be abstracted into a particle.

2． Reference system

When describing the motion of an object, the object used as a reference is called a reference system.

3． Distance and Displacement

Distance is the length of the movement trajectory of the particle, and distance is a scalar quantity.

Displacement represents the change in the position of an object. The size is equal to the straight-line distance between the starting and ending positions, and the direction is from the starting position to the ending position. Displacement is a vector quantity.

When an object makes one-way linear motion, the magnitude of the displacement is equal to the distance.

4. Speed ??Average speed and instantaneous speed

Speed ??is the physics that describes how fast an object moves, v=Δx/Δt, speed is a vector, and its direction is the same as the direction of motion.

Average speed: the speed of a moving object at a certain time (or a certain process).

Instantaneous speed: the speed of a moving object at a certain moment (or a certain position), and the direction is along the tangent direction of the point on the trajectory where the particle is located.

5. Uniform linear motion

In linear motion, the motion in which the displacement of an object is equal in any equal time is called uniform linear motion. Uniform linear motion is also called motion with constant speed.

6. Acceleration

Acceleration is a physical quantity that describes the speed of speed change. It is equal to the ratio of the speed change to the time taken to occur. The definition formula is a=Δv/Δt=(vt-v0)/Δt, Acceleration is a vector whose direction is the same as the change in velocity, regardless of the direction of velocity.

7. Use an electric spark timer (or electromagnetic dot timer) to measure the speed

The electromagnetic dot timer uses an AC power supply, and the working voltage is below 10V. The spark timer uses AC power and the working voltage is 220V. When the frequency of the power supply is 50Hz, they all hit a point every 0.02s.

If is shorter, the average speed will be closer to the instantaneous speed at that point

8. Use an electric spark timer (or electromagnetic dot timer) to explore how the speed of a uniformly variable linear motion changes with time

When a uniformly variable linear motion moves, the speed of an object at the middle moment of a certain period of time is equal to the speed of that period of time. Average speed

9. Laws of uniform linear motion

Speed ??formula: Displacement formula:

Displacement speed formula: Average speed formula:

10. The speed-time image of the law of uniform linear motion

The ordinate represents the speed of the object's movement, and the abscissa represents time

Image meaning: represents the change of the object's speed with time

① means that the object moves in a straight line with uniform speed;

② means that the object moves in a straight line with uniform acceleration;

③ means that the object moves in a straight line with uniform deceleration;

①②③The ordinate of the intersection point indicates that the speeds of the three moving objects are equal;

The area of ??the shaded area in the figure indicates the displacement of ② within the time period from 0 to t1

11. Displacement time image of uniform linear motion

The ordinate represents the displacement of the object, and the abscissa represents time

Image meaning: represents the change of the object's displacement with time

< p>① means that the object is at rest;

② means that the object is moving in a straight line at a uniform speed;

③ means that the object is moving in a straight line at a uniform speed;

①②③The ordinate of the intersection point Indicates that the displacements of three moving objects are the same when they meet.

12． Free fall motion

(1) Concept: The movement of an object starting to fall from rest only under the action of gravity is called free fall motion

(2) Essence: Free fall motion is the initial velocity The acceleration of linear motion with zero uniform acceleration is called the acceleration of free fall, also called the acceleration of gravity.

(3) Rule: v= gt; h=; v2= 2gh.

13． Galileo's study of free fall motion

The scientific research process: (1) General observation of the phenomenon (2) Proposing hypotheses (3) Using logic to draw inferences (4) Testing the inferences through experiments (5 ) Revise and promote hypotheses

The core of Galileo's scientific thinking method is the harmonious combination of experiment and logical reasoning.

14. Force

(1) Force is the effect of one object on another object. If there is a force-receiving object, there must be a force-exerting object.

(2) The three elements of force: force has magnitude, direction, point of action, and is a vector.

(3) How to express force: You can use a line segment with an arrow to represent force.

15. Gravity

(1) Generation: It is the force exerted on objects due to the attraction of the earth. It is not equal to the universal gravitation, but is a component of the universal gravitation.

(2) Size: G=mg, g is the acceleration of free fall.

(3) Direction: It is a vector, the direction is vertically downward, it cannot be said to be vertically downward.

(4) Center of gravity: the point of action of gravity. The center of gravity does not need to be on the object. For uniform regular objects, the center of gravity is at its geometric center. For irregularly shaped thin plate objects, the position of the center of gravity can be determined by the suspension method. For objects with uneven mass distribution, the position of the center of gravity is not only related to the shape of the object, but also related to the distribution of mass within the object.

16. Deformation and Elasticity

(1) Elastic deformation: The shape or volume of an object changes under the action of force, which is called deformation. Some objects can return to their original shape after deformation. This deformation is called elastic deformation.

(2) Elastic force: An object that undergoes elastic deformation exerts a force on the object in contact with it because it wants to return to its original shape. This force is called elastic force.

(3) Conditions for production: direct contact, mutual extrusion and elastic deformation.

(4) Direction: Opposite to the direction of deformation, acting on the object that forces the object to deform, the pulling force of the rope points along the rope in the direction of the rope contraction. The pressure and supporting force are both elastic forces. The direction are perpendicular to the contact surface of the object.

(5) The size of spring elastic force: within the elastic limit, x is the deformation amount, k is determined by the nature of the spring itself, and is related to the thickness, length and material of the spring.

17． Sliding friction and static friction

(1) Sliding friction: When an object slides on the surface of another object, it will receive a force from the other object that hinders its sliding. This force is called sliding friction.

(2) Conditions for the generation of sliding friction: a. Direct contact b. Rough contact surface c. Relative motion d. Elasticity

(3) Direction of sliding friction : Always opposite to the direction of relative motion, it can be in the same direction as the movement, it can be in the opposite direction of the movement, it can be resistance, it can be power. Both moving and stationary objects can be affected by sliding friction.

(4) The magnitude of sliding friction: , is the positive pressure, is the kinetic friction factor, has no unit, and is determined by the material and roughness of the contact surface. (0 1, N has nothing to do with G)

(5) Static friction: When an object has a tendency to move relative to the surface of another object, it is hindered by another object

(6) Conditions: a. Direct contact b. Rough contact surface c. Relative movement tendency d. Elasticity

(7) Direction: always opposite to the direction of relative movement trend, available Judgment by balancing act. , can be resistance or power, and moving objects can also be subject to static friction.

(8) Size:

18. The synthesis and decomposition of force B

(1) Resultant force and component force: The effect produced by a force is the same as the effect produced by several original forces acting together. This force is called those forces. The resultant force. Those forces are called components of this force. Finding the resultant of several forces is called the synthesis of a force, and finding the components of a force is called the decomposition of a force.

(2) The synthesis method of force: use the parallelogram rule. The resultant force decreases as the angle increases.

The range of the resultant force of two forces

The resultant force is unique.

(3) Decomposition method of force: Using the parallelogram rule, the decomposition of force is the inverse operation of the synthesis of force. The same force can be decomposed into countless pairs of component forces with different sizes and directions. One has How to decompose intelligence depends on the actual situation.

(4) Under what circumstances is the decomposition of force unique? ①The directions of the resultant force and the two component forces are known (not on the same straight line), and find the magnitude of the two component forces. ② Given the magnitude and direction of the resultant force and one component force, find the magnitude and direction of the other component force.

19. ***The equilibrium of an object under the action of a point force A

(1) The concept of ***point force: ***Point force refers to all forces that act on a point or the extension of the line of action intersects at a point force.

(2) The concept of equilibrium of an object under the action of a point force: The state in which an object can remain stationary or move in a straight line at a uniform speed is called a state of equilibrium.

(3) ***The equilibrium condition of an object under the action of a point force: the total external force on the object is zero, that is, Fsum = 0, that is, the acceleration of the object is zero. If you use the orthogonal decomposition method, you can establish the following two equations (F plus x=0 and F plus y=0).

20. Mechanical Unit System A

(1) The International System of Units (SI) is a unit system composed of basic units and units derived from these basic units.

(2) There are three basic units in mechanics: the unit of length is the meter, the international symbol is m, the unit of mass is the kilogram, the international symbol is ㎏, and the unit of time is the second, the international symbol is s.

21. Newton's First Law A

(1) Galileo's Ideal Experiment

(2) Content of Newton's First Law

(3) The relationship between force and motion:

①The wrong understanding in history is that "movement must be maintained with force"---------Aristotle's point of view;

②The correct understanding is "Motion does not require force to maintain, force is the reason for changing the state of motion of an object."

(4) Understanding of "changing the state of motion of an object" - the change of the state of motion refers to the change of speed. The change of speed includes the change of speed magnitude and speed direction. The change of speed means the existence of acceleration. .

(5) Maintaining its own motion state is the essential attribute of all objects, and this essential attribute is inertia. Mass is a measure of the amount of inertia.

22． Experiment: Explore the relationship between acceleration, force, and mass A

(1) Experimental idea: The basic idea of ????this experiment is to use the control variable method.

(2) Experimental plan: The physical quantities to be measured in this experiment include mass, acceleration and external force. To use a balance to measure mass, you need to study how to measure acceleration and external forces.

①Measurement of acceleration: The most commonly used solution is to use a dot timer and calculate the acceleration based on the difference ΔS=aT2 between the displacements within consecutive equal times T.

②Measuring the external force on the object: Since our above-mentioned method of measuring acceleration can only be applied to uniform linear motion, we must provide a constant external force to the object and measure this external force.

23． Newton's second law B

(1) The content and mathematical expression of Newton's second law: The content of Newton's second law of motion is that the acceleration of an object is directly proportional to the net external force and inversely proportional to the mass. The direction of acceleration is the same as the direction of the net external force. F combined=ma.

(2) The relationship between force and motion:

①The resultant external force on an object produces the resultant acceleration of the object:

When the object is subjected to the magnitude of the resultant external force and the direction remains unchanged, and the direction of the net external force and the direction of the initial velocity are along the same straight line and in the same direction, then the object will move in a straight line with uniform acceleration.

When the magnitude and direction of the net external force on an object remain unchanged, and the direction of the net external force and the direction of the initial velocity are along the same straight line and in opposite directions, the object will move in a straight line with uniform deceleration.

When the net external force on an object changes with time, the net acceleration of the object also changes with time.

②The direction of acceleration is the direction of the resultant external force.

③The relationship between acceleration and the resultant external force is instantaneous. (Force has acceleration)

④ When an object is acted upon by several forces, the acceleration of the object is equal to the vector sum of the accelerations produced by each force when they exist alone, that is, a=a1+a2+a3...

24. Newton's third law

(1) Contents of Newton's third law of motion: The action and reaction forces between two objects are always equal in magnitude and opposite in direction, acting on a straight line.

Application of Newton's Law of Motion 1

There are two basic types of questions about force and motion: one is to determine the motion of the object by knowing the force on the object; the other is Knowing the motion of the object, determine the force on the object.

Force analysis, the force on the object, F combined, the movement of the object

F combined = ma

Application 2 of Newton's law of motion

Overweight And weightlessness

(1) When an object has vertical upward acceleration, the force exerted by the object on the dynamometer is greater than the gravity of the object. This phenomenon is called overgravity. F=m(g+a)

(2) When an object has vertical downward acceleration, the force exerted by the object on the dynamometer is less than the gravity of the object. This phenomenon is called weightlessness. F=m(g-a)

(3) The state in which the force reading of the object on the dynamometer is equal to zero is called a state of complete weightlessness. A liquid in a completely weightless state exerts no pressure on the walls of the vessel.

(4) When an object is in a state of overweight or weightlessness, the gravity exerted by the object does not change.

25. Synthesis and decomposition of motion

(1) The relationship between combined motion and divided motion

① Isochrony The time experienced by combined motion and divided motion is equal

② Independence: An object participates in several partial motions at the same time. Each partial motion proceeds independently and is not affected by other partial motions

③ Equivalence The superposition of the laws of each partial motion is exactly the same as the law of the combined motion. Effect

(2) Operation rules

The synthesis and decomposition of motion refers to the synthesis and decomposition of various physical quantities that describe motion, that is, speed and displacement, because they are vectors.

Therefore, they all follow the parallelogram law

26. The rules of flat tossing motion

(1) Nature of motion

The flat tossing motion is a uniformly variable speed curved motion, which is The combined motion of uniform linear motion in the horizontal direction and uniform linear motion in the vertical direction (free fall motion), the trajectory of flat throw motion is a parabola

(2) Law of motion

In the horizontal direction: aX=0; VX=V0; Speed ??and displacement: S=; V=

27. Uniform circular motion

Uniform circular motion is a curved motion. The linear velocity direction of each point is along the tangent direction, but the magnitude remains unchanged; The direction of acceleration always points to the center of the circle, and the magnitude remains unchanged, but it is a variable-speed motion and a variable-acceleration motion

28. Linear velocity, angular velocity and period

(1) Linear velocity V: Describes the speed of motion, V=S/t, S is the arc length passing within t, the unit is m/s

(2) Angular velocity ω: Describes the speed of rotation, ω=θ/t, the unit is rad/s

(3) Period T: the time to complete a complete circular motion

(4) The relationship between the three: V=rω, ω=2π/T V=2πr/T

29. Centripetal acceleration

Direction: always points along the radius to the center of the circle. In uniform circular motion, the magnitude of centripetal acceleration remains unchanged

Size: a=V2/r =rω2

30. Centripetal force

(1) Centripetal force is the force that causes centripetal acceleration of an object. The direction is the same as the direction of centripetal acceleration. The magnitude is determined by Newton's first The second law can be obtained: F=m V2/r=m rω2

(2) Centripetal force is named according to the effect of the force. It is not a special force. It can be elastic force, friction force or several forces. The centripetal force for uniform circular motion is the resultant external force on the object. (Note: There is no centripetal force in the force analysis)

31. The law of universal gravitation

(1) Content: Any two objects in nature attract each other. The magnitude of the gravitational force is proportional to the product of the object's mass m1 and m2, and is proportional to the square of the distance r between them. Inversely proportional.

(2) Expression: F = G. G = 6.67×10-11N?m2/kg2 (Cavendish measurement)

32. Artificial Earth Satellite

(1) The centripetal force of the satellite in uniform circular motion around the earth is given by The gravitational force it receives provides:

F million = F direction, that is, G = m G =mω2r G =

(2) Geosynchronous satellite: It is stationary relative to the ground and rotates with the earth. synchronized satellites. For satellites to be synchronized with the earth's rotation, the following conditions must be met:

1. The satellite orbits the earth in the same direction as the earth's rotation, and the satellite's operation period is the same as the earth's rotation period (that is, equal to 24 hours).

2． The circular orbit of the satellite must coincide with the Earth's equatorial plane.

3． The satellite's orbit is at a certain altitude (36,000 kilometers above the ground).

33. Cosmic speed

(1) First cosmic speed: v = 7.9 km/s

A is the minimum speed for launching artificial earth satellites

p>

B is the maximum speed orbiting the earth (orbiting speed v = ).

(2) The speed of the second universe: v =11.2 km/s

(3) The speed of the third universe: v = 16.7 km/s

34 ． Work A

(1) Two necessary factors for doing work: force and displacement in the direction of the force

(2) Definition: The work done by a force on an object is equal to the magnitude of the force , the product of the magnitude of the displacement, the cosine of the angle between the force and the displacement. That is,

(3) Work is a scalar quantity, unit: J;

(4) The physical meaning of positive and negative work: a force doing positive work on an object means that the force promotes the movement of the object Action; a force doing negative work on an object means that the force hinders the movement of the object.

W1+W2+W3+

(5) Method for finding total work: W total=

Method for finding work: W=Pt

△EK

35． Power A

(1) Concept: P=W/t=FV (F and V are in the same direction) Unit: Watt (W)

(2) Understanding: Average power P＝ W/t＝F

Instantaneous power P＝FV The difference between rated power and actual power

(3) Physical quantity: a physical quantity indicating how fast an object does work

36. Gravitational potential energy, the relationship between gravitational work and gravitational potential energy A

(1) Concept: gravitational potential energy EP=mgh

Gravity work WG=mg(h1-h2)

The increase in gravitational potential energy △Ep=mgh2-mgh1 WG= -△Ep

(2) Understanding: (1) The work done by gravity has nothing to do with the path and is only related to the height difference between the starting and ending positions; (2) Gravity When positive work is done, the gravitational potential energy decreases, and when gravity does negative work, the gravitational potential energy increases; (3) The work done by gravity is equal to the decrease in gravitational potential energy; (4) The gravitational potential energy is relative, unique to the earth, that is, the relative gravitational potential energy sexual and systematic.

37． Elastic potential energy A

The elastic potential energy of a spring is only related to the stiffness coefficient and deformation of the spring.

38． Kinetic energy A

Kinetic energy: EK= mv2 scalar

39. Kinetic energy theorem A

Content of kinetic energy theorem: The work done by the resultant force on an object in a process is equal to the change in kinetic energy of the object in the process

W＝mv22－mv12

40． Law of Conservation of Mechanical Energy B

1. Content: In an object system where only gravity or elastic force does work, kinetic energy and potential energy can be converted into each other, while the total mechanical energy remains unchanged.

2． Condition: Only gravity or elastic force does work

3. Formula: E2=E1, EK2+EP2=EK1+EP2

4. Methods to judge the conservation of mechanical energy: (1) Conservation conditions (2) Whether the total amount of EK+EP remains unchanged

41. Use a dot timer to verify the law of conservation of mechanical energy A

1. The dot timer is an instrument that uses AC power. When the frequency of the alternating current is 50Hz, it dots every 0.02s. The working voltage of the electromagnetic dotting timer is below 10V, while the working voltage of the spark timer is 220V

2． Use the formula mv2/2=mgh to verify the constant law of mechanical energy. The distance between points 1 and 2 of the selected paper tape should be close to 2mm

3. There is no stopwatch or scale in the equipment

42. Law of Conservation of Energy A

Energy will neither disappear nor be created. It will only be converted from one form to other forms, or transferred from one object to another. During the process, the total amount of energy remains unchanged

43. Energy and directionality of energy conversion and transfer A

1. Non-renewable energy: cannot be generated again and cannot be reused

2. Energy dissipation: In the process of energy utilization, some energy is converted into the internal energy of the surrounding environment, and humans cannot collect this internal energy for reuse

3. Although energy can be transformed and transferred, the transformation and transfer are directional

44. Limitations of classical mechanics A

(1) The scope of application of classical mechanics: suitable for low speeds Motion, macroscopic objects, weak interactions.

(2) Classical mechanics is a special case of relativity and quantum mechanics under certain conditions,

45. Charge Law of Conservation of Charge A

(1) Two types of charges in nature: when a glass rod rubs against silk, the glass rod becomes positively charged; when a rubber rod rubs against fur, the rubber rod becomes negatively charged.

(2) The elemental charge e= 1.6×10-19 C. The charge of all objects is an integer multiple of the elemental charge.

(3) There are three ways to charge objects: contact electrification, friction electrification, and induction electrification. No matter which method is used, it is the transfer of charge between objects or from a part of the object. To the other part, the total amount of charge is unchanged.

(4) Law of conservation of charge

46. Coulomb's Law A

(1) The conditions for the establishment of Coulomb's Law: point charges at rest in vacuum.

(2) The conditions under which charged bodies can be regarded as point charges: If the distance between charged bodies is much larger than the size of their own linear dimensions, the shape and size of the charged bodies can affect the interaction force. Negligible, such a charged body can be regarded as a point charge.

(3) Content of the law: The interaction force between two stationary point charges in a vacuum is proportional to the product of their charges and inversely proportional to the square of their distance. The interaction force The direction is on the line connecting them.

(4) Expression: F＝　　, k= 9×109 Nm2/ c2.

47. Electric field Electric field strength Electric field line A

(1) Electric field: the special substance that exists around the charge. Objects and fields are two ways of material existence.

(2) The definition of electric field strength: the ratio of the electric field force experienced by a charge placed at a certain point in the electric field to its electric charge.

Expression: E＝F/q　. The unit of electric field strength is N/C. The strength of the electric field has nothing to do with the charges placed in the field, but is determined only by the electric field itself.

(3) Regulation of the direction of electric field intensity: The direction of the electric field intensity at a certain point in the electric field is the same as the direction of the electric field force exerted by the positive charge at that point. The direction of the electric field force exerted by the negative charge at this point is opposite.

(4) Characteristics of electric field lines: (1) Electric field lines start from positive charges or infinity and end at infinity or negative charges; (2) Electric field lines do not intersect in the electric field; (3) ) Where the electric field is stronger, the electric field lines are denser. Therefore, the electric field lines can not only vividly represent the direction of the electric field, but also roughly represent the relative magnitude of the electric field intensity.

48. Magnetic field Magnetic field lines A

(1) Magnetic field: There is a magnetic field around magnets and currents.

(2 (Magnetic field direction: At a certain point in the magnetic field, the direction of the force exerted on the north pole of the small magnetic needle, that is, the direction in which the north pole points when the small magnetic needle is stationary, is the direction of the magnetic field at that point.

(3) Characteristics of magnetic flux lines: a. Magnetic flux lines are imaginary lines; b. Two magnetic flux lines will not intersect; c. Magnetic flux lines must be closed

50. Ampere's rule for magnetic fields A

(1) Discovery of the magnetic effect of electric current: 1820 Denmark Oersted

(2) Ampere's rule: energized straight wire, energized ring, Electrified solenoid

51. Magnetic induction intensity magnetic flux A

(1) Definition of magnetic induction intensity: When the energized wire is perpendicular to the direction of the magnetic field, the ampere force on the wire is equal to the current The ratio of the product of wire lengths, that is, B=F/IL. Unit: tex (T)

(2) Direction of magnetic induction intensity: direction of magnetic field

(3) Magnetic flux: through The number of magnetic field lines passing through a closed circuit

52. The left-hand rule A of the magnitude of Ampere's force (1) Ampere's force: the force exerted on a current-carrying wire in a magnetic field. It is called Ampere's force

(2) The calculation formula of Ampere's force: F=BIL;

When the energized wire is perpendicular to the direction of the magnetic field, the Ampere's force has a maximum value F=BIL; When the wire is parallel to the direction of the magnetic field, the Ampere force has a minimum value of F=0.

(3) Left-hand rule: Stretch out your left hand so that your thumb is perpendicular to the other four fingers and in contact with the palm of your hand. In the same plane, let the magnetic field lines pass through the palm of the hand and point the four fingers in the direction of the current. The direction pointed by the thumb is the direction of the ampere force exerted by the current-carrying wire in the magnetic field.

53. Direction of force A

(1) Lorentz force: the force exerted by magnetic field on moving charges.

(2) Ampere force is the macroscopic manifestation of Lorentz force.

p>

(3) The left hand rule determines the direction of the Lorentz force: Stretch out your left hand, make the thumb perpendicular to the other four fingers, and in the same plane as the palm, let the magnetic induction lines penetrate into the palm of the hand, and Point the four fingers in the direction of the movement of the positive charge. At this time, the direction pointed by the thumb is the direction of the Lorentz force exerted by the moving positive charge in the magnetic field. The direction of the force on the negative charge is opposite to that of the positive charge. /p>

54. Electromagnetic induction phenomenon and its applications A

(1) In 1831, the British physicist Faraday discovered the electromagnetic induction phenomenon.

(2) Electromagnetic induction Phenomenon: The phenomenon of using a magnetic field to generate current is called electromagnetic induction. The current generated by electromagnetic induction is called induced current.

(3) The conditions for generating induced current: the magnetic flux passing through the closed loop changes.< /p>

55. Law of electromagnetic induction A

(1) Induced electromotive force: the electromotive force generated in the phenomenon of electromagnetic induction.

(2) Law of electromagnetic induction: induction in a circuit The magnitude of the electromotive force is proportional to the rate of change of the magnetic flux passing through this circuit

(3) Formula: ((single coil)

56. Electromagnetic waves A

(1) Maxwell predicted the existence of electromagnetic waves, and Hertz confirmed the existence of electromagnetic waves.

(2) Maxwell’s electromagnetic field theory:

a. A changing magnetic field produces an electric field b. A changing electric field produces a magnetic field

(3) Characteristics of electromagnetic waves:< /p>

a. Electromagnetic waves can propagate in vacuum;

b. Electromagnetic waves themselves are a kind of material, and electromagnetic waves have energy;

c. Wavelength, frequency and wave speed: c= (c wave speed; wavelength; f frequency)

d. Speed ??of electromagnetic waves in vacuum: c=3.00×108m/s

(4) Electromagnetic spectrum:

a. In descending order of wavelength: radio waves, infrared rays, visible light, ultraviolet rays, X-rays, rays

b. Different electromagnetic waves have different frequencies and therefore have different Features

① Radio waves are suitable for communication and broadcasting. The microwaves used in microwave ovens are also a type of radio waves

② Infrared rays have thermal effects. Applications include: night vision devices, infrared photography, infrared rays Remote Sensing

③ Visible light can cause vision, and different colors of light are electromagnetic waves with different frequency ranges

④ Ultraviolet rays have higher energy and can sterilize; they have fluorescence effects and can excite Many substances emit light

⑤ X-rays have strong penetrating power and can see through the human body and check whether there are defects inside metal parts

⑥ X-rays have strong penetrating power and can treat certain cancers , detecting whether there are defects inside metal parts

57. Utilization and prevention of static electricity A

(1) Principle of static electricity utilization: Charged particles are affected by the electric field force and will move towards the electrode, and finally be adsorbed on the electrode.

Positively charged particles will move toward the negative pole under the action of the electric field force, while negatively charged particles will move toward the positive pole.

Examples: electrostatic dust removal, electrostatic spraying, electrostatic copying, electrostatic flocking, lightning rods, etc.

(2) Static electricity hazard: Discharge sparks may cause the explosion of flammable materials. The discharge of static electricity in the human body when in contact with conductors such as metal can cause a tingling sensation.

(3) Methods to prevent static electricity: conduct static electricity away in time. Such as humidifying the air, adding conductive metal wires to carpets, etc.

58． The meaning of the technical parameters of common household appliances such as electric heaters and incandescent lamps A

(1) Working principle of electric heaters: utilizing the thermal effect of electric current. Such as electric iron, rice cooker, electric water heater, etc.

If an electric heater has a power of 1000 watts and works for 1 hour, it consumes ___1___ degrees.

(2) A certain household incandescent lamp is marked "220V, 40W". The rated voltage of this incandescent lamp is _220__ volts __ AC ___ current, and the rated power working under this rated voltage is ___40W __Watts.

59. Safe use of electricity and conservation of electricity A

(1) Household appliances should have ground wires, and household circuits should have fuses.

(2) Human body safety voltage: no higher than 36V. When the same voltage or current is applied to the human body, alternating current is more harmful.

(3) Ways to save electricity: Do not put household appliances on standby and replace lighting appliances with energy-saving lamps; reduce the resistance of transmission wires; increase the transmission voltage to reduce the transmission current. Principle: Heating of transmission lines Q=I2R=(P/U)2R

60. Resistors, capacitors and inductors A

(1) Resistors: Electric irons, rice cookers, electric water heaters, incandescent lamps, etc. are all resistors.

The role of a resistor: convert electrical energy into heat energy.

Resistor parameters: Resistance, represented by R. The greater the resistance, the greater the resistance of the resistor to the current.

The unit is: ohm.

(2) Capacitor: It is a device that stores electric charge.

The earliest capacitor that appeared was the Leyden jar

The function of a capacitor is to store charge; in an AC circuit, the capacitor functions to communicate AC and isolate DC.

Capacitance parameters: Capacitance, represented by C, C=Q/U; the larger the capacitance, the greater the ability to store charge.

The larger the facing area of ??the capacitor plates and the smaller the distance between the plates, the greater the capacitance of the capacitor.

Unit: Farad F, 1F=106uF=1012pF

(3) Inductor: Coil

The function of the inductor: hinder the change of current; in AC circuit It plays the role of: passing DC and blocking AC.

Inductor parameters: self-inductance coefficient, represented by L.

The larger the coil, the more turns it has, and the iron core it has, the greater its self-inductance coefficient.

Examples: transformers, ballasts in fluorescent lamps, electromagnets, etc.

61. How generators and motors use energy and their role in industrial development A

(1) Generator: Convert other forms of energy into electrical energy. There are AC and DC generators.

The working principle of the generator: electromagnetic induction. When the rotor rotates, the magnetic flux in the coil changes, thereby generating an induced current in the coil.

(2) Electric motor: Convert electrical energy into mechanical energy.

There are also AC and DC motors

The working principle of the motor: the energized wire will be affected by the magnetic field force (ampere force) in the magnetic field.

62. Common sensors and their applications A

(1) Sensor: a component that can convert non-electrical quantities such as temperature, force, sound, light, etc. into electrical quantities.

(2) Common sensors:

(1). Temperature sensor:

a. Bimetal temperature sensor Principle: Different materials have different thermal expansion coefficients.

b. Thermistor temperature sensor Principle: The resistance of the thermistor decreases as the temperature increases.

(2) Light sensor:

Photoresistor: When light is irradiated, the resistance of the photoresistor decreases.

(3) Pressure sensor: The capacitance of the capacitor changes with the distance between the two plates (the capacitance increases as the distance decreases)