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Magnetic Fields. It is a Field Force AP Physics. Electricity and Magnetism. For many years it was believed electricity and magnetism were separate and unrelated. . Ions of + and - charge. In chemistry you learned protons and electrons have charges equal in magnitude but opposite in charge.

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Magnetic fields

Magnetic Fields

It is a Field Force

AP Physics


Electricity and magnetism
Electricity and Magnetism

  • For many years it was believed electricity and magnetism were separate and unrelated.


Ions of and charge
Ions of + and - charge

  • In chemistry you learned protons and electrons have charges equal in magnitude but opposite in charge.

  • Therefore atoms and molecules can have charge and areas of partial charge (δ).

  • These electrical charges can attract (if opposite) or repel (if the same) one another.




Electrical force
Electrical Force

qA

qB

What does this equation look like?

F

=

K

r2

Gravitational Force!!


Electrical force1
Electrical Force

qA

qB

Charge (q) is measured in coulombs!

F

=

K

r2

The charge on one electron is -1.60× 10-19 coulombs. This is the elementary charge!


Electrical force2
Electrical Force

qA

qB

F

=

K

r2

qA and qB is the charges on the objects, measured in coulombs(C).

r is the distance between the objects in meters(m).

K is the constant in 9.0 × 109 N∙m2/C2.

F is force in Newtons (N)


Magnetic fields1
Magnetic Fields

  • Some objects are magnetized, have North and South polar ends.

  • Using iron filings, this is the magnetic field of a simple polarized piece of metal.

  • Metals such as Aluminum, Nickel, Cobalt, and Neodymium readily create magnetic fields.


The magnetic poles
The Magnetic Poles

  • The poles are at opposite ends of a magnet.

  • Opposite poles attract one another, like poles repel one another.

  • The upper picture shows the repulsion of two like poles.

  • The Earth itself also has a magnetic field, which is why compasses work!



What causes magnets
What Causes Magnets? radiation from the Sun!

  • Magnetic fields are caused by d-orbital electrons spinning in the same direction.

  • The more the fields of the atoms are aligned, the stronger the magnet.

  • Magnetic Fields travel from the North to South pole!



Electrical flow and magnetic fields
Electrical Flow and Magnetic Fields radiation from the Sun!


Putting electricity and magnetism together
Putting Electricity and Magnetism Together radiation from the Sun!

In 1820 it was first observed that electrical current flowing through a wire caused a magnet to turn at right angles to the current.


Electromagnetism
Electromagnetism radiation from the Sun!

  • Faraday concluded that as current (I) flowed through a metal it created a magnetic field around it.

  • A compass always pointed at right angles to the electrical flow because it was in the magnetic field.


Solenoids
Solenoids radiation from the Sun!

  • A coil of wire with electrical current running through it is called a solenoid.

  • The magnetic field of each loop adds to the magnetic field of other loops.

  • The South Pole is where current flows in.

  • The North Pole is where the current flows out.


Solenoids1
Solenoids radiation from the Sun!

  • Grip a solenoid by the right hand with fingers curling in the same direction of the current.

  • This way the thumb points to the north pole of the magnetic field.


Solenoids2
Solenoids radiation from the Sun!


The strength of the magnetic field inside a solenoid
The strength of the magnetic field radiation from the Sun!inside a solenoid.

is called the magnetic permeability of a vacuum.

N is the number of turns in the coil.

ℓ is the length of the solenoid.

I is the current.


The right hand rule
The Right Hand Rule radiation from the Sun!


The right hand rule1
The Right Hand Rule radiation from the Sun!


Magnetic force
Magnetic Force radiation from the Sun!

  • Electromagnets exert a magnetic force . The direction of the force is dependent on the direction of the current.


Relating it to an electrical current
Relating it to an Electrical Current radiation from the Sun!


Force on a current carrying wire in a magnetic field
Force on a current carrying wire in a magnetic field. radiation from the Sun!

Iis the electrical current measured in amperes(A).

ℓis the length of the wire measured in meters(m).

Bis the magnetic field strength measured in teslas(T).

T= 1N/A∙m

Force is still in Newtons (N).


Force on a current carrying wire in a magnetic field1
Force on a current carrying wire in a magnetic field. radiation from the Sun!

Angle θ is the angle between the current and the magnetic field.


Force of a magnetic field on a charged moving particle
Force of a magnetic field on a charged, moving particle. radiation from the Sun!

qis the charge on the particle in coulombs(C).

vis the velocity of the particle measured in meters per second(m/s).

Bis the magnetic field strength measured in teslas(T).

Force is still in Newtons (N).

Angle θ is the angle between the direction of the velocity and the magnetic field.


Force of a magnetic field on a charged moving particle1
Force of a magnetic field on a charged, moving particle. radiation from the Sun!

Why does the particle have to be charged??

Neutral particles, such as neutrons, are not deflected by magnetic fields!!


The strength of the magnetic field around a wire with current decreases the further away from the wire.

is called the magnetic permeability of a vacuum.

This was discovered by H.C. Ørsted and is often referred to as Ørsted’s Equation.


Electromagnetic induction

Electromagnetic Induction current decreases the further away from the wire.

Faraday’s brilliant insight!!


Electromagnetic induction1
Electromagnetic Induction current decreases the further away from the wire.

  • Oersted was the first to observe that an electric current through a wire creates an effect on a compass.

  • Faraday, in order to prove a magnetic field was created by electrical current, decided to see if the reverse was true.

  • Faraday was able to get a magnetic field to create an electrical current, proving electricity and magnetism were a unified force.


Electromagnetic induction2
Electromagnetic Induction current decreases the further away from the wire.

Moving a magnet through an electrical coil causes an electrical current to be induced!


What was the impact
What was the impact?? current decreases the further away from the wire.

  • Electrical motors and electrical generators which power our modern world.

  • Even modern electrical generators powered by nuclear or hydroelectric stations use magnets to generate electrical current.



The end
The End!! generate electrical current.


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