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Physics II - B01

TABLE OF CONTENTS

Electric Charge (Điện tích)

  1. Positive or Negative
  2. Conserved
    • Charge is not created in the process of rubbing two objects together.
    • The electrification is due to a transfer of charge from one object to another.
  3. \(q = N \cdot e\)

\(N\) is an integer
\(|e| = 1.6 \times 10^{-19} (C) \)

Electrical Condutors (Chất dẫn điện)

  • Electrical conductors are materials in which some of the electrons are free electrons.
    • Free electrons are not bound to the atoms
    • Electrons can move freely through the material.
    • Good conductor: copper, aluminum and silver.
    • When a good conductor is charged in a small region, the charge readily distributes itself over the entire surface of the material

Electrical Insulators (Chất cách điện)

  • Electrical insulators are materials in which all of electrons are bound to atoms.
    • Electrons can not move freely through the material.
    • Good insulators: glass, rubber and wood.
    • When a good insulator is charged in a small region, the charge is unable to move to other regions of the material.

Semiconductors (Chất bán dẫn)

  • The electrical properties of semiconductors are somewhere between those of insulators and conductors.
    • Semiconductor materials: silicon and germanium.
    • Used in making electronic chips.
    • The electrical properties of semiconductors can be changed by the addition of controlled amounts of certain atoms to the material.

Electrostatics

Electrostatics: Tĩnh điện

Charging by induction

  • Charging by induction (hiện tượng cảm ứng điện từ) requires no contact with the object inducing the charge.
  • Examples: See more on powerpoint.

Coulomb’s laws

  • The force is a conservative force (chỉ phụ thuộc vào điểm đầu và điểm cuối, không phụ thuộc vào đường đi).
  • The force is inversely proportional to the square of the separation.(Inverse - square law)

  • Like charges repel $\simeq$ repel
  • Unlike charges attract $\simeq$ attract

Superposition principle (Nguyên lý chồng chất)

  • The resultant force on any one charge equals the vector sum of the forces exerted by the other individual charges that are present.

Electric dipole (Lưỡng cực điện)

Assignments

\[S^2 = 2F^2 - 2.cos2\alpha.F^2\] \[S^2 = 2F^2.(1-cos2\alpha) = 4.F^2.sin^2\alpha\] \[S = 2.F.sin\alpha\] \[S = \frac{k.q^2.d}{(r^2 + \frac{d^2}{4})^\frac{3}{2}}\]

Other references