The document discusses the properties of electrostatics and the interactions between charged particles. It states that like charges repel each other, while opposite charges attract. This is illustrated through diagrams of positive and negative charges interacting. The relationships between attractive and repulsive forces based on charge are repeated several times. The document also includes an image of an electroscope, which is used to detect charge through the movement of gold leaves.
- Coulomb's Law describes the electrostatic force of attraction or repulsion between two charged objects, and follows an inverse-square relationship with distance. The force is directly proportional to the product of the charges and inversely proportional to the square of the distance between them.
- The elementary charge, as determined by Millikan's oil drop experiment, is the lowest possible charge carried by a single electron or proton. Ordinary objects have charges that are integer multiples of this elementary charge.
- Niels Bohr used the similarity between Coulomb's Law and Newton's Law of Gravitation to develop his atomic model of the hydrogen atom, with the electron orbiting the proton like planets orbiting the Sun.
Resistivity is a measure of how effectively a material slows the flow of electricity, with insulators having high resistivity and conductors having low resistivity. Resistance depends on the material's resistivity as well as the length and cross-sectional area of the material. Resistance increases with length and decreases with increasing cross-sectional area. Superconductivity causes resistance to become zero below a critical temperature.
1) The document discusses the dual nature of radiation and matter, explaining that both photons and particles like electrons exhibit both wave-like and particle-like properties.
2) It describes the Davisson-Germer experiment, where electrons were diffracted by nickel crystals, demonstrating their wave-like behavior and allowing calculation of their de Broglie wavelength.
3) The results of the experiment matched what was predicted by de Broglie's hypothesis that moving particles have an associated wavelength inversely proportional to their momentum.
The wave-particle duality and the double slit experimentSatyavan65
From the Udemy online course "The weird World of Quantum Physics - A primer on the conceptual foundations of Quantum Physics": https://www.udemy.com/quantum-physics/?couponCode=SLIDESHCOUPON
Central forces are forces that always act toward or away from a fixed point, with a magnitude that depends only on the distance from that point. A central force F on a particle P can be expressed as F = r f(r), where f(r) is a function of the distance r from the fixed point and r is the unit vector along the radius. Examples of central forces include gravitational attraction and electrostatic force. Central forces are conservative, have no torque, and cause angular momentum to remain constant.
Notes for Atoms Molecules and Nuclei - Part IIIEdnexa
- The document provides information about various topics in nuclear physics including de Broglie wavelength, composition and size of nucleus, isotopes, nuclear binding energy, radioactive decay, and nuclear fission.
- It defines key terms like isotopes, isobars, isotones, mass defect, nuclear binding energy, radioactive decay, half-life, decay constant, and describes the properties and characteristics of alpha particles, beta particles, and gamma rays.
- Mathematical relationships are given for radius of nucleus, mass defect, nuclear binding energy, radioactive decay law, and calculating half-life from the decay constant. Examples are provided to illustrate various concepts.
The document discusses the properties of electrostatics and the interactions between charged particles. It states that like charges repel each other, while opposite charges attract. This is illustrated through diagrams of positive and negative charges interacting. The relationships between attractive and repulsive forces based on charge are repeated several times. The document also includes an image of an electroscope, which is used to detect charge through the movement of gold leaves.
- Coulomb's Law describes the electrostatic force of attraction or repulsion between two charged objects, and follows an inverse-square relationship with distance. The force is directly proportional to the product of the charges and inversely proportional to the square of the distance between them.
- The elementary charge, as determined by Millikan's oil drop experiment, is the lowest possible charge carried by a single electron or proton. Ordinary objects have charges that are integer multiples of this elementary charge.
- Niels Bohr used the similarity between Coulomb's Law and Newton's Law of Gravitation to develop his atomic model of the hydrogen atom, with the electron orbiting the proton like planets orbiting the Sun.
Resistivity is a measure of how effectively a material slows the flow of electricity, with insulators having high resistivity and conductors having low resistivity. Resistance depends on the material's resistivity as well as the length and cross-sectional area of the material. Resistance increases with length and decreases with increasing cross-sectional area. Superconductivity causes resistance to become zero below a critical temperature.
1) The document discusses the dual nature of radiation and matter, explaining that both photons and particles like electrons exhibit both wave-like and particle-like properties.
2) It describes the Davisson-Germer experiment, where electrons were diffracted by nickel crystals, demonstrating their wave-like behavior and allowing calculation of their de Broglie wavelength.
3) The results of the experiment matched what was predicted by de Broglie's hypothesis that moving particles have an associated wavelength inversely proportional to their momentum.
The wave-particle duality and the double slit experimentSatyavan65
From the Udemy online course "The weird World of Quantum Physics - A primer on the conceptual foundations of Quantum Physics": https://www.udemy.com/quantum-physics/?couponCode=SLIDESHCOUPON
Central forces are forces that always act toward or away from a fixed point, with a magnitude that depends only on the distance from that point. A central force F on a particle P can be expressed as F = r f(r), where f(r) is a function of the distance r from the fixed point and r is the unit vector along the radius. Examples of central forces include gravitational attraction and electrostatic force. Central forces are conservative, have no torque, and cause angular momentum to remain constant.
Notes for Atoms Molecules and Nuclei - Part IIIEdnexa
- The document provides information about various topics in nuclear physics including de Broglie wavelength, composition and size of nucleus, isotopes, nuclear binding energy, radioactive decay, and nuclear fission.
- It defines key terms like isotopes, isobars, isotones, mass defect, nuclear binding energy, radioactive decay, half-life, decay constant, and describes the properties and characteristics of alpha particles, beta particles, and gamma rays.
- Mathematical relationships are given for radius of nucleus, mass defect, nuclear binding energy, radioactive decay law, and calculating half-life from the decay constant. Examples are provided to illustrate various concepts.
The document discusses different forces including magnetism. It describes four fundamental forces: gravity, electromagnetic, strong force, and weak force. It then focuses on magnetism, explaining that it is a physical phenomenon produced by the motion of electric charge that results in attractive and repulsive forces. The document discusses magnetic field lines, electromagnets, naturally magnetic materials like iron and magnetite, and magnetic motors. It hypothesizes that magnetism may have an infinite range like gravity and that gravity may be a form of magnetism. Finally, it suggests that controlling forces could allow controlling the universe.
1. Rutherford's alpha scattering experiment demonstrated that the positive charge and most of the mass of an atom are concentrated in a small, dense nucleus at the center. 2. The binding energy curve shows that binding energy per nucleon increases initially with mass number, peaks at iron-56, then decreases, making very large and very small nuclei unstable. 3. Radioactive decay follows predictable exponential laws, with the decay constant λ representing the probability of decay per unit time and half-life the time for half the nuclei to decay.
i am student of M.Sc (Physics) in university of sindh. it is my first book on high energy physics and i will also upload the new version of this book soon. so please read this book and give me feed back on my email address.
Stationary waves are produced by the superposition of two progressive waves of equal amplitude and frequency travelling in opposite directions. They have nodes where there is no displacement and antinodes where the displacement is at a maximum. In a stationary wave, the waveform does not move through the medium and energy is not carried away from the source. All particles between two nodes vibrate in phase.
Light and matter exhibit wave-particle duality, behaving as both particles and waves. When light passes through two slits, it creates an interference pattern like a wave. However, when using a sensitive film, tiny light particles are observed, suggesting particle behavior. Einstein acknowledged two necessary but logically unconnected theories of light. The double slit experiment results cannot be fully explained by treating light solely as particles or waves. While one theory was that photons interacted to cause interference, experiments making the light extremely dim found it was virtually impossible for two photons to be present at the same time. Thus light and matter demonstrate both wave and particle properties and cannot be described by only one model.
The document discusses various topics related to wave optics and the physics of light, including:
- The wave nature of light and how it explains phenomena like reflection, refraction, the formation of shadows and spectra.
- Huygens' principle which states that each point on a wavefront is the source of secondary wavelets and the new wavefront is the tangent to these wavelets.
- The laws of reflection which state that the angle of incidence equals the angle of reflection.
- Refraction and how the speed and wavelength of light changes when passing from one medium to another.
- Interference and coherence - the addition of waves to form a resultant wave, and how coherent sources are required
Magnetic Effects Of Current Class 12 Part-2Self-employed
The document discusses various topics related to the magnetic effects of electric current:
1. It defines Lorentz force and Fleming's left hand rule for determining the direction of force on a current-carrying conductor in a magnetic field.
2. It describes the forces experienced by moving charges and current-carrying conductors in both uniform electric and magnetic fields.
3. It provides the definition of the ampere based on the forces experienced between two parallel current-carrying conductors.
In this video i have explained nuclear models. There are three types of nuclear models 1. liquid drop model
2. shell model
3.collective model
I explained liquid drop model in simple way.
Class 12th physics current electricity ppt Arpit Meena
1. The document discusses key concepts related to electric current including definitions of current and conventional current, drift velocity, current density, Ohm's law, resistance, resistivity, conductance, conductivity, and temperature dependence of resistance.
2. It also covers color codes for carbon resistors, series and parallel combinations of resistors, definitions of emf and internal resistance of cells, and series and parallel combinations of cells.
3. The document provides formulas and explanations for many important electrical concepts in a comprehensive yet concise manner.
The new quantum theory proposes that photons have an eccentric nucleus of mass and charge that causes them to spin and travel in a sinusoidal wave path. This explains phenomena such as wave-particle duality and the formation of electromagnetic waves. Photons generate electric and magnetic fields as they spin due to the movement of their off-center nucleus, and interference occurs when photons' angular momentums constructively add. The theory aims to replace the temporary solution of wave-particle duality with a unified model of photons exhibiting both wave and particle properties due to their spinning eccentric nucleus.
1. Lord Rutherford discovered the nucleus through alpha particle scattering experiments, finding that atoms consist of a small, dense, positively charged nucleus surrounded by orbiting electrons.
2. The nucleus contains positively charged protons and neutral neutrons, collectively called nucleons. The number of protons is the atomic number and the total number of protons and neutrons is the mass number.
3. Isotopes are atoms with the same atomic number but different mass numbers, such as the three isotopes of hydrogen: deuterium, ordinary hydrogen, and tritium.
Rutherford fired alpha particles at a gold foil and observed that most passed through undeflected, while some were deflected at small angles and a very small number rebounded backwards. From this, Rutherford concluded that atoms have a small, dense nucleus containing most of the atom's mass, with electrons orbiting the nucleus, explaining why most alpha particles were unaffected but a few interacted with the nucleus. This led to the discovery of the nuclear model of the atom.
1. Rutherford's alpha scattering experiment provided evidence for the nuclear model of the atom, showing that the mass and positive charge of an atom are concentrated in a small, dense nucleus.
2. The binding energy curve shows that binding energy per nucleon initially rises with atomic mass number before peaking at iron-56 and then decreasing, indicating relative nuclear stability.
3. Radioactive decay follows first-order kinetics and the rate of decay is characterized by the disintegration constant λ, with the half-life period giving the time for half the radioactive nuclei to decay.
Fleming's right hand rule describes how to determine the direction of induced current in a conductor moving through a magnetic field. It involves positioning the fingers and thumb of the right hand perpendicular to each other, with the thumb pointing in the direction of motion, forefinger pointing in the direction of the magnetic field, and middle finger then pointing in the direction of induced current. Fleming's left hand rule operates similarly but relates the thumb, forefinger and middle finger to the direction of force, magnetic field, and current respectively. A rotating magnetic field is produced when a three-phase winding is energized, with the field poles shifting positions continuously around the stator rather than remaining fixed.
Helical Methode - To determine the specific chargeharshadagawali1
1. This experiment aims to determine the specific charge (e/m) of electrons using the helical coil method. A cathode ray tube is placed inside a solenoid and electrons are accelerated towards the screen and deflected by a transverse AC voltage.
2. The resulting motion of the electrons is helical due to the magnetic field produced by the solenoid. By measuring the pitch of the helix, the e/m ratio can be calculated using the given formula.
3. The calculated value of e/m is 1.6 × 1011 C/kg with a percent error of 8.57% compared to the standard value of 1.75 × 1011 C/kg.
The document discusses different forces including magnetism. It describes four fundamental forces: gravity, electromagnetic, strong force, and weak force. It then focuses on magnetism, explaining that it is a physical phenomenon produced by the motion of electric charge that results in attractive and repulsive forces. The document discusses magnetic field lines, electromagnets, naturally magnetic materials like iron and magnetite, and magnetic motors. It hypothesizes that magnetism may have an infinite range like gravity and that gravity may be a form of magnetism. Finally, it suggests that controlling forces could allow controlling the universe.
1. Rutherford's alpha scattering experiment demonstrated that the positive charge and most of the mass of an atom are concentrated in a small, dense nucleus at the center. 2. The binding energy curve shows that binding energy per nucleon increases initially with mass number, peaks at iron-56, then decreases, making very large and very small nuclei unstable. 3. Radioactive decay follows predictable exponential laws, with the decay constant λ representing the probability of decay per unit time and half-life the time for half the nuclei to decay.
i am student of M.Sc (Physics) in university of sindh. it is my first book on high energy physics and i will also upload the new version of this book soon. so please read this book and give me feed back on my email address.
Stationary waves are produced by the superposition of two progressive waves of equal amplitude and frequency travelling in opposite directions. They have nodes where there is no displacement and antinodes where the displacement is at a maximum. In a stationary wave, the waveform does not move through the medium and energy is not carried away from the source. All particles between two nodes vibrate in phase.
Light and matter exhibit wave-particle duality, behaving as both particles and waves. When light passes through two slits, it creates an interference pattern like a wave. However, when using a sensitive film, tiny light particles are observed, suggesting particle behavior. Einstein acknowledged two necessary but logically unconnected theories of light. The double slit experiment results cannot be fully explained by treating light solely as particles or waves. While one theory was that photons interacted to cause interference, experiments making the light extremely dim found it was virtually impossible for two photons to be present at the same time. Thus light and matter demonstrate both wave and particle properties and cannot be described by only one model.
The document discusses various topics related to wave optics and the physics of light, including:
- The wave nature of light and how it explains phenomena like reflection, refraction, the formation of shadows and spectra.
- Huygens' principle which states that each point on a wavefront is the source of secondary wavelets and the new wavefront is the tangent to these wavelets.
- The laws of reflection which state that the angle of incidence equals the angle of reflection.
- Refraction and how the speed and wavelength of light changes when passing from one medium to another.
- Interference and coherence - the addition of waves to form a resultant wave, and how coherent sources are required
Magnetic Effects Of Current Class 12 Part-2Self-employed
The document discusses various topics related to the magnetic effects of electric current:
1. It defines Lorentz force and Fleming's left hand rule for determining the direction of force on a current-carrying conductor in a magnetic field.
2. It describes the forces experienced by moving charges and current-carrying conductors in both uniform electric and magnetic fields.
3. It provides the definition of the ampere based on the forces experienced between two parallel current-carrying conductors.
In this video i have explained nuclear models. There are three types of nuclear models 1. liquid drop model
2. shell model
3.collective model
I explained liquid drop model in simple way.
Class 12th physics current electricity ppt Arpit Meena
1. The document discusses key concepts related to electric current including definitions of current and conventional current, drift velocity, current density, Ohm's law, resistance, resistivity, conductance, conductivity, and temperature dependence of resistance.
2. It also covers color codes for carbon resistors, series and parallel combinations of resistors, definitions of emf and internal resistance of cells, and series and parallel combinations of cells.
3. The document provides formulas and explanations for many important electrical concepts in a comprehensive yet concise manner.
The new quantum theory proposes that photons have an eccentric nucleus of mass and charge that causes them to spin and travel in a sinusoidal wave path. This explains phenomena such as wave-particle duality and the formation of electromagnetic waves. Photons generate electric and magnetic fields as they spin due to the movement of their off-center nucleus, and interference occurs when photons' angular momentums constructively add. The theory aims to replace the temporary solution of wave-particle duality with a unified model of photons exhibiting both wave and particle properties due to their spinning eccentric nucleus.
1. Lord Rutherford discovered the nucleus through alpha particle scattering experiments, finding that atoms consist of a small, dense, positively charged nucleus surrounded by orbiting electrons.
2. The nucleus contains positively charged protons and neutral neutrons, collectively called nucleons. The number of protons is the atomic number and the total number of protons and neutrons is the mass number.
3. Isotopes are atoms with the same atomic number but different mass numbers, such as the three isotopes of hydrogen: deuterium, ordinary hydrogen, and tritium.
Rutherford fired alpha particles at a gold foil and observed that most passed through undeflected, while some were deflected at small angles and a very small number rebounded backwards. From this, Rutherford concluded that atoms have a small, dense nucleus containing most of the atom's mass, with electrons orbiting the nucleus, explaining why most alpha particles were unaffected but a few interacted with the nucleus. This led to the discovery of the nuclear model of the atom.
1. Rutherford's alpha scattering experiment provided evidence for the nuclear model of the atom, showing that the mass and positive charge of an atom are concentrated in a small, dense nucleus.
2. The binding energy curve shows that binding energy per nucleon initially rises with atomic mass number before peaking at iron-56 and then decreasing, indicating relative nuclear stability.
3. Radioactive decay follows first-order kinetics and the rate of decay is characterized by the disintegration constant λ, with the half-life period giving the time for half the radioactive nuclei to decay.
Fleming's right hand rule describes how to determine the direction of induced current in a conductor moving through a magnetic field. It involves positioning the fingers and thumb of the right hand perpendicular to each other, with the thumb pointing in the direction of motion, forefinger pointing in the direction of the magnetic field, and middle finger then pointing in the direction of induced current. Fleming's left hand rule operates similarly but relates the thumb, forefinger and middle finger to the direction of force, magnetic field, and current respectively. A rotating magnetic field is produced when a three-phase winding is energized, with the field poles shifting positions continuously around the stator rather than remaining fixed.
Helical Methode - To determine the specific chargeharshadagawali1
1. This experiment aims to determine the specific charge (e/m) of electrons using the helical coil method. A cathode ray tube is placed inside a solenoid and electrons are accelerated towards the screen and deflected by a transverse AC voltage.
2. The resulting motion of the electrons is helical due to the magnetic field produced by the solenoid. By measuring the pitch of the helix, the e/m ratio can be calculated using the given formula.
3. The calculated value of e/m is 1.6 × 1011 C/kg with a percent error of 8.57% compared to the standard value of 1.75 × 1011 C/kg.
16. 7-16 電流 Electric current
7.3 電功率及電流的熱效應
學習目標
閱讀完這節,你應該能夠…
1. 解釋在導體內移動的自由電子如何損失能量
2. 理解電功率與電能之間的關係
3. 針對電器,能應用電功率,電流,電壓及電 阻之間
的關係。
4. 針對電池,能夠應用電功率、電流、電位差 之間的
關係方程式
5. 應用能量守恆定解釋電路裡頭,電池與電器 之間能
量轉換過程。
電路中,電能產生與消耗
1. 電池利用化學能將正(負)電荷經由電池內部從負(正)極推向正
(負)極,使電荷獲得了電位能。
2. 電器是一種消耗電位能而轉變成其他能量形式的裝置,例
如:馬達將電能轉換成力學能、喇叭將電能轉換成聲能、電
解池則將電能轉換成化學能…。
3. 電能產生(或消耗)的快慢稱為電功率
定義:
E
P V I
t
說明:
電池兩端電壓為 V,通過電流為 I 獲得的電能為
Q
I
t
Q I t eU Q V
所產生的電功率 P(將電能轉換為熱能)為
eU Q V I t V
P I V
t t t
單位:瓦特
電流熱效應焦耳定律
1.電流流經電阻時,電荷所減少的電位能部分轉換成電阻器的 熱
能
電能損耗率:
2
2 V
P IV I R
R
說明:電荷載子在移動過程中會與導體中的原子碰撞,而將部
份動能移轉給原子,加劇原子的振動能量傳遞給原子成為原
子的振動動能 溫度上升
外界給予的能量被消耗,成為流經導體的熱能。
圖 7-20 電爐 From wiki
圖 7-19 電池提供電能,讓電器 R
使用。因此電器 R 可視為消耗電
能。
21. 7-21電流 Electric current
7.4 電流、電位差及電阻的測量
學習目標
閱讀完這節,你應該能夠…
1. 理解檢流計原理
2. 理解安培計的設計原理,與使用安培計測量電 流。
3. 理解伏特計的設計原理,與使用伏特計測量電 壓。
4. 解釋對電路元件進行測量電壓或電流時候,得到的
數字從來都不是準確值。
5. 針對電阻大小差異,選擇不同的伏特計、安 培計接
法。
6. 知道 三用電表,與如何操作
7. 理解惠司通電橋原理,並應用該原理來解題
檢流計 Galvanometer
1.安培計、伏特計的核心元件
2.結構:一個線圈和一對永久磁鐵所構成
3.原理:(可參考ch 8)
當電流通過線圈時,會使線圈在磁場中偏轉。
利用附在線圈上的指針代表偏轉的角度,以指示電流大小
線圈電阻要極小,才不會影響測量值
安培計 Ammeter
1.由檢流計併聯一低電阻所構成,本身為一低電阻
2.電路符號
3.使用時候與待測電路 串聯
4.所測得之電流 小於 未接安培計時候的電流
未接任何安培計前,路上的電
流大小: i
R r
接上安培計,安培計讀數:
A
A
i
R r r
圖 7-24 檢流計 構造圖
圖 7-25 安培計外觀與內部結構
𝑟𝐴
𝑟
G
𝒓 𝒈
𝐼𝑔𝑰
𝐼𝑟
黑 紅
22. 7-22 電流 Electric current
伏特計 Voltmeter
1.由檢流計串聯一高電阻所構成,本身為高電阻
2.電路符號
3.使用時候與待測電路 並聯
4.所測得之電壓 小於 未接伏特計時的電壓
說明:
沒有接上伏特計時,電阻兩端的電位
差
RV i R R
R r
1
RV
r
R
併聯伏特計之後,電流會額外流過
伏特計,總電流為 i’
V i R R
R r
1 1 1
VR R r
改變安培計與伏特計的測量範圍
1.測量範圍增為原來的 n 倍,需要併聯電阻 R
1
Ar
R
n
說明:假設 I 為安培計可通過的最大電流
2.測量範圍增為原來的 n 倍需要串聯一個電 ( 1) VR n r
說明:假設 V 為伏特計可測得的最大電壓
r
現
代
生
活
到
處
都
是
電
流
-
不
論
是
我
們
使
用
的
電
子
裝
置
,
或
家
中
的
供
電
網
圖 7-26 伏特計
23. 7-23電流 Electric current
常用的電阻測量方式
1.高電阻值的電阻測量方式
結果: = A
V
R R R
i
測量值 實際值 必須 AR R
說明:
伏特計測得的電壓是包含安培計的總電壓
2.低電阻值的電阻測量方式
結果:
1
V
RV
R
RI
R
實際值
測量值
實際值 必須 RV>>R。
說明:安培計測得的電流等於包含通過伏特計的總電流
3.惠司同電橋法 Wheatstone Bridge
電橋又稱作橋式電路,是一種電路類型
在兩個並聯支路當中,插入一個支路,將兩個並聯支路橋接
起來的電路
在電學上,常用來 測定電阻或校正電阻的電路。
說明:
如圖,R1、R3 為固定電阻及 R2 為可調整的 可變電阻,BD
間之 VG 為檢流計,Rx 是一個未知電阻器
調整 R1、R2、R3,使得電流計中的電流為零,因為沒有電
流,所以 BD 兩端沒有電位差,於是可以得到 2 3
1
x
R R
R
R
圖 7-27 惠司通電橋示意圖
+ -
A B
R
A
V
+ -
A B
R
A
V
28. 7-28 電流 Electric current
7. 若將右示電路圖中的開關 S 切斷,伏
特計 V 的讀值為 12 伏特。此時安培計
A 的讀值為多少安培?
8. 一個電儀器的線圈中所能允許的最大
電流是 2.4 安培,它的電阻是 20 歐姆。現在要把它與正有
15 安培電流流動的某電器串聯,而不影響此電器原有的電
流;要如何方可避免此儀器因通過過大電流而被燒燬?
大考試題觀摩
9.某生利用如圖 1 所示的電路測量一個待測電阻 R 的 I-V 曲線。
試問電路中,X,Y,及 Z 各為何種器材?
(A) X:電阻箱; Y:伏㈵計; Z:安培計 (B) X:伏特計;
Y:安培計; Z:電阻箱 (C) X:安培計; Y:電阻箱; Z:
伏特計(D) X:伏特計; Y:電阻箱; Z:安培計 (E) X:安培
計; Y:伏特計; Z:電阻箱 [93.指定科考]
練習題答案
1.(1)6Ω (2)22V 2.3Ω 3.ABE 4.0.72 5.4Ω 6.
11
8
Ω 7.
0.9 8.並聯 3.8 歐姆之電阻 9. B
29. 7-29電流 Electric current
直流電路網路分析原則(補充教材)
1. 基本原則
等電位位置可以合併。
電流自然流向: 高 電位流到 低 電位
2. 進階原則:極限法
對於無窮網路可以數學-極限的觀念,配合代數法決
說明:
3. 進階原則:對稱法因電路對稱而產生等電位點
說明:
4. 進階原則:三角轉 Y 型(進階教材:基本電路學)
簡易說明:
在三角形電路中: 3 2 1
1 2 3
( )
AB
R R R
R
R R R
,在 Y 型電路:
3 2ABR r r
兩者效應相同故
3 2 1
3 2
1 2 3
( )R R R
r r
R R R
BC 間的等效電阻:
1 3 2
1 3
1 2 3
( )
BC
R R R
R r r
R R R
AC 間的等效電阻:
1 2 3
1 2
1 2 3
( )
AC
R R R
R r r
R R R
A
B
C
D
E
F G
H
I
I
30. 7-30 電流 Electric current
例題11.:電阻的串聯與併聯-無限連結
如圖所示無限多個電阻中,除 M,N 之間的電阻外,其他大小都
同為 R,M 與 N 之間的電阻選為______時,A,B 間的總電阻為定
值,與組成電路的單元重複幾個無關,且 A、B 間的總電阻為______
答:( 3 -1)R,( 3 -1)R
類題:如圖,求 AB 間等效電阻。答:8Ω
例題12.:簡易電路等位點
12 根同長度的電阻 R 之電阻線,構成一立方體,求(1)兩對頂角
之兩頂點 A、G 間的總電阻?(2)求兩頂點 H、F 間之電阻?
答:
答:
5 3
(1) (2)
6 4
R R
例題13.:三角形轉 Y 型
範例 演練
A
B
C
D
E
F G
H
I
I
31. 7-31電流 Electric current
如圖所示的電路,已知 A、B、C、D、E 五個電阻分別為 10
Ω 、5 Ω 、5 Ω 、10 Ω 、5 Ω ,試計算 X 和 Y 兩點間的等效
電阻為何?
答:7 Ω
類題:下圖中 AB 之間的等效電阻為 (A)15 (B)5 (C)
3
10
(D)
10
7
(E)
7
10
歐姆。 答:C
課後 練習題
A
B
C
D
E
10
5
5
5
10
X Y
32. 7-32 電流 Electric current
克西合夫定則(補充資料)
1.電路 electric circuit:由電力裝置和元件, 按一定方式連接起
來,為電荷流通提供了路徑的總體,也叫電子線路或稱電氣迴
路。
2.電路運作原理:電量守恆定律及能量守恆定律
3.克西合夫迴路定則(能量守恆定律)
規則 1.:電流與迴路方向,同方向(順向)
則電阻降低電位(消耗電能)、電池增加電位(提供電能)
規則 2.:電流與迴路方向,反方向(逆向)
則電阻提高電位、電池降低電位 (類比為充電狀態)
圖 7-30 左:規則 1, 右:規則 2
實際應用:
如圖所示,假設此回路方向為順時針,電流方向也是順時針。
圖 7-31 簡單電流回路的電位升降判斷
4.克西荷夫節點定則(電量守恆)
規則:電路上某一結點,流入的總電流 等於 流出的總電
流 in outI I
圖 7-32 多重迴路的電流可用節點定則判定
a b
i
R a b
i
R
真
實
電
池
a b
r
c d
R
a
i
電
位
V