Electromagnetism

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Electromagnetism - PowerPoint PPT Presentation

Electromagnetism. Forces in nature:. How does matter interact? Four Fundamental Forces: Long range: Gravity Mid Range: Electromagnetic Short Range: Strong and Weak. Electric Charge (~Mass). Two types of electric charge: positive and negative Unit of charge is the coulomb [C]

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Presentation Transcript

Electromagnetism

Forces in nature:

• How does matter interact?
• Four Fundamental Forces:
• Long range: Gravity
• Mid Range: Electromagnetic
• Short Range: Strong and
• Weak

Electric Charge (~Mass)

Two types of electric charge: positive and negative

Unit of charge is the coulomb [C]

Charge of electron (negative) or proton (positive)is

Charge is quantized

Charge is conserved

Electric Force (~Gravity)

• The electric force between charges q1 and q2 is
• repulsive if charges have same signs
• (b) attractive if charges have opposite signs

Like charges repel and opposites attract !!

Coulomb\'s Law

Coulomb’s law:

Force by q1 on q2

Coulomb’s constant in vacuum:

Direction: along the line joining the two charges

Repulsive or attractive

The superposition principle

If many charges are present:

Net force is on any charge is the vector sum of the forces from all the individual charges

In general:

The electric field

The electric field at a point is the force acting on a test charge q at that point divided by the charge q

For a test charge q

has the direction and sense of the force on a positive charge.

Electric field created by a point charge Q

is outwards a positive charge and inwards a negative charce

The superposition principle for fields

The electric field due to a collection of N point charges is the vector sum of the individual electric fields due to each charge:

Flows With Sources

(http://ocw.mit.edu/ans7870/8/8.02T/f04/visualizations/vectorfields/02-particleSource/02-ParticleSource_320.html)

Flows with sinks

(http://ocw.mit.edu/ans7870/8/8.02T/f04/visualizations/vectorfields/01-particleSink/01-ParticleSink_320.html)

Circulating flows

(http://ocw.mit.edu/ans7870/8/8.02T/f04/visualizations/vectorfields/03-particleCirculate/03-PartCircMotion_320.html)