James Clerk Maxwell Michael Faraday

What is magnetism?…a phenomena in which certain materials exert attractive/repulsive forces on other materials.

These materials contain a region where these forces can be detected. (Magnetic fields)

Where do magnetic fields occur?

Where do magnetic fields occur?

How do Magnetic fields work?

Field lines move away from the north pole.

Field lines move towards the south pole.

Magnetic Field of the Earth

North magnetic pole located at south geographic pole.

South magnetic pole located at north geographic pole.

Magnetic Field Strength on a Charged Moving

Object The strength of a magnetic field (B) is related to the amount of magnetic force (F) that is applied to a moving test charge when it is at a given location in the field.B =

Fmagnetic qυq = test charge

magnitude

υ = speed of the charge

Sample ProblemA proton moving east experiences an upward

force of 8.8 x 10-19 N due to the Earth’s magnetic

field. The field hasa strength of 5.5 x 10-5 Tesla’s (T) to the

north. Find thespeed of the proton.q = 1.60 x 10-

19 CB = 5.5 x 10-

5 TFmagnetic = 8.8 x 10-

19 N

B = Fmagnetic qυυ = Fmagnetic qB

υ = 8.8 x 10-19 N _ = (1.60 x 10-19 C) (5.5 x 10-5 T)

1.0 x 105 m/s

Direction of magnetic force

The direction of the magnetic force is perpendicular to the plane of the magnetic field and to the direction of the charge.

USE THIRD RIGHT HAND

RULE!!!

Magnetic force in current-carrying wires

Current carrying wires that are placed in a magnetic field also experience a magnetic force.

WIRE

IF

The magnitude of the magnetic force can be written in terms of the current (I) flowing through the length of the wire (L).

Magnetic force in current-carrying wires

F = BIL

Sample ProblemA 10.0 m long powerline carries a

current of 20.0 Aperpendicular to the Earth’s magnetic

field of 5.5 x 10-5 T. What is the magnetic force

experienced by the power line? F = BIL

I = 20.0 A

B = 5.5 x 10-5 T L = 10.0

m

F = (5.5 x 10-5 T)(20.0 A)(10.0 m) =

0.011 N

Magnetic fields from electricity

Charges that are in motion (an electrical current) produce magnetic fields.

Magnetic field moves around a wire with a current in a circular fashion.

Which direction???

Right Hand Rule

1.Thumb goes in the direction of the current.

2. Fingers wrap around wire in the direction of the magnetic field.

Electromagnets

Arranging wire in a coil and running a current through produces a magnetic field that is similar to a bar magnet.

ElectromagnetsThese long, helically wound coils of wire are referred to as solenoids.