 Magnets can be created one of two ways: Naturally found in the Earth. They are called lodestones. It is permanently magnetized. Using electricity to make an electromagnet. These can be turned on and off to be used when needed.

 Every magnet has two poles. North South  A single magnetic pole has never been isolated!  Like electrical charges: Two similar poles will repel. Two different poles will attract.

 Electricity and magnetism started off as two different studies in the early 1800s.  Then, while teaching a physics class, Hans Christian Oersted discovered that when he turned a circuit on and off, it deflected a compass needle on his desk.  This accidental discovery jump started perhaps the most important era in science.

 There are two important relationships between electric fields and magnetic fields. Changing a magnetic field creates an electric field. (Faraday and Henry) Changing an electric field creates a magnetic field. (Maxwell)

 We already know that a stationary source charge has an electric field.  However, if we move that source charge it will have both an electric field AND a magnetic field surrounding it.  Therefore there are two places we see a magnetic field: Surrounding a permanent magnet. Surrounding a moving electric charge.

 Magnetic field lines always go from the north to the south pole.

Magnetic Force Charge Velocity Magnetic Field Angle of motion through field

 Important characteristics of charges moving through a magnetic field: When a charge moves parallel to the magnetic field, the is no magnetic force acting on the charge. When θ ≠ 0, the magnetic force acts in a direction perpendicular to both velocity and field. The magnetic force exerted on a positive charge is in the opposite direction of the magnetic force exerted on a negative charge.

 Magnetism is a three-dimensional force. To determine the direction of the magnetic force we use the right-hand rule. (This is for positive charges!) Point your fingers in the direction of velocity. Curl your fingers towards the field. (X means into the paper, means out of the paper.) Direction of your thumb is the direction of the magnetic force.

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Current Length of wire

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 Remember that the magnetic force is like all other forces we have seen so far! Gravity Tension Human Electric  They can all be set equal to: F = ma

 An electron (m= 9.11 x kg) moves at a speed of 6.0 x 10 6 m/s perpendicular to a magnetic field. The circular path the electron takes has a radius of 1.3 x m. What is the magnitude of the magnetic field?