Magnetism (3, Review). Like poles repel Unlike poles attract

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Magnetism (3, Review)

Like poles repel

Unlike poles attract

Magnetic Field Lines vs. Electric Field Lines

Magnetic Dipole Electric Dipole

What happens when you bring a compass near a bar magnet?

The north indicator of the compass will point toward the south pole of a magnet.

This is also why a compass points north, it's lining up with the earth's magnetic poles.

Source of Magnetic Fields• Electrical Charge in motion.

– Currents occur at the atomic level in atoms due to the orbits of electrons around the nucleus.

– The intrinsic spin (+1/2, -1/2) is critical in the case of magnetism.

Moving Charges in a magnetic Field

•Magnetic fields cause moving charges to curve

•http://homepages.ius.edu/kforinas/physlets/magnetism/magnetH.html

•http://www.youtube.com/watch?v=thtrYYoI7AM

Field around a wire• http://www.launc.tased.edu.au/online/

sciences/physics/Lenz%27s.html

• Demo!

Lenz’s Law• http://www.launc.tased.edu.au/online/

sciences/physics/Lenz%27s.html

• Demo!

Questions•Describe the forces acting on this floating magnet

Questions•What are the vector and non-vector quantities related to magnetism?

Questions•Draw bar magnets and field lines as follows:

•N-N

•N-S

•S-S

Questions•:Draw a horseshoe magnet

QuestionsDraw a wire with a current

•Show the field lines

QuestionsAdd compasses to all drawings above

http://www.magnet.fsu.edu/education/tutorials/index.html

Questions•How do you produce a magnetic field?

•Describe the forces acting on this floating magnet

•What are the vector and non-vector quantities related to magnetism?

•Draw bar magnets and field lines as follows:

•N-N

•N-S

•S-S

•Draw a horseshoe magnet

•Draw a wire with a current

•Show the field lines

Add compasses to all drawings above

http://www.magnet.fsu.edu/education/tutorials/index.html

Questions•Draw a wire moving through a magnetic field

•What is equation?

•Show direction of induced current

Questions•Draw a wire moving through a magnetic field

•What is equation?

•Show direction of induced current

•EMF

Questions

•Draw a wire with a current in a magnetic field

•What is equation?

•What are the forces acting on the wire?

Questions

•Draw a beam of protons moving through a magnetic field

•What is equation?

•Show the forces

•What if the velocity is increased?

Questions•Draw a wire moving through a magnetic field

•What is equation?

•EMF

•Show direction of induced current

•Draw a wire with a current in a magnetic field

•What is equation?

•What are the forces acting on the wire?

•Draw a beam of protons moving through a magnetic field

•What is equation?

•Show the forces

•What if the velocity is increased?

Questions•Draw a wire in a magnetic field

•Show the direction to produce maximum potential difference

•Show a direction to produce no potential difference

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