Motion of a Charged Particles

Motion of a Charged Particles

When the velocity of a charged particle is perpendicular to a uniform magnetic field, the particle moves in a circular path in a plane perpendicular to B

Magnetic forces do NOT do any work on moving charges

Berapa besar jari-jari lintasan r ?

Bq

mvR

R

vmqBv

FF SB

2

Applications• A charge moving with a velocity v in the presence of both an

electric field E and a magnetic field B experiences both an electric force qE and a magnetic force qv x B.

• The total force (the Lorentz force) acting on the charge is

Sources of Magnetic Field : electric current

Jean-Baptiste Biot (1774–1862) and Félix Savart (1791–1841) performed quantitative experiments on the force exerted by an electric current on a nearby magnet.

Biot–Savart law :

where μo is a constant called the permeability of free space

μo = 4π x 10-7 T∙m/A

The total magnetic field B created at some point by a current of finite size:

Contoh : Magnetic Field due to a Finite Straight Wire

Magnetic Field due to a Circular Current Loop

Ampere’s Law

Solenoid We can use Ampere’s law to calculate the magnetic field strength inside an ideal solenoid. The line integral of B along this loop is

What happens if the length of the solenoid is finite?

Toroid

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