Physics II - B02

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TABLE OF CONTENTS

• Introduction
• Definition
• Electric Field Lines (Đường sức từ)
• Motion of Charged Particles
• Uniform Electric Field (Điện trường đều)
• Continuos Charge Distribution
• Assignment
• New Words
• Other references

Electric Field

Introduction

• The electric force is a field force.
• Field forces can act through space.
• The effect is produced even with no physical contact between objects.

Definition

• An electric field is said to exist in the region of space around a charged object. (source charge)
• The electric field is defined as the electric force on the test charge per unit charge.

Electric Field Lines (Đường sức từ)

• go out from the positive, go into the negative.
• cannot split, merge, cross each other.
• Number of field lines attached a charge ~ the amount of charge.

Motion of Charged Particles

Uniform Electric Field (Điện trường đều)

• Eletron’s motion is parabolic while between the plates.

Continuos Charge Distribution

Assignment

\[dE = \frac{k.dq}{x^2 + r^2}\] \[\frac{dE_x}{dE} = \frac{x}{(x^2 + r^2)^\frac{1}{2}}\] \[dE_x = \frac{x}{(x^2 + r^2)^\frac{1}{2}}.\frac{k.dq}{x^2 + r^2}\]

We have $dE_y = 0$. So:

\[E = E_x = \int dE_x = \int \frac{kx.dq}{(x^2 + r^2)^\frac{3}{2}} = \frac{kx}{(x^2 + r^2)^\frac{3}{2}}.Q\]

New Words

• radial altitude: Máy đo độ cao vô tuyến
• vanish: biến mất

Other references

• MIT Physics 2
• Michel van Biezen
• Khan Academy

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