Solenoids.notebook
January 21, 2016
Solenoids
Oersted's Principle ~ a charge moving through a conductor produced a circular magnetic field around the conductor.
Left Hand Rule for a Straight Conductor
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If a conductor is held in the left hand with the left thumb pointing in the direction of electron flow ( ­ terminal to + terminal) then the curled fingers will point in the direction of the magnetic field lines.
­ Wire going out of the page
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Wire going into the page
X
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Solenoids.notebook
January 21, 2016
A Solenoid ~ a coil of electrical wires. it may have a moveable iron core.
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electron flow
_
Left Hand Rule for a Coil
If a coil is grasped in the left hand with the curled fingers representing the direction of electron flow, the thumb points in the direction of the magnetic field inside the coil. (Points north)
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Solenoids.notebook
January 21, 2016
Factors Affecting the Magnetic Field in a Coil
The strength of a magnetic field is related to the degree of concentration of its magnetic field lines.
Weak magnetic field
Strong magnetic field
1. Current in the coil ~ the more current there is the greater the concentration of magnetic field lines in the core. I α B. If we double the current we double the magnetic field strength.
B2 = B1(I2/I1)
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Solenoids.notebook
January 21, 2016
2. Number of Loops ~ The more loops that are wound the stronger the magnetic field. n α B. If we double n, we double B.
B2 = B1(n2/n1)
3. Type of Core Material ~ core material becomes an induced magnet. Therefore, iron works better than air. Aluminum has no real affect. B α μ.
Magnetic Permeability (μ) ~ the factor by which the a core material increase the magnetic field strength.
μ = magnetic field strength with material
magnetic field strength in vacuum
B2 = B1(u2/u1)
4. Size of coil ~ the smaller the coil the stronger the magnetic field.
B α 1/r
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Solenoids.notebook
January 21, 2016
HW pg 589 # 2, pg 600­601 # 20­23
Make notes on pg 589 Applications of Electromagnetism
Ferromagnetism ~ iron, nickel, cobalt
Paramagnetism ~ oxygen, aluminum
Diamagnetism ~ copper, silver, water
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