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