magnetism chapters 36 & 37. general info. moving charges cause magnetism magnets have magnetic...
TRANSCRIPT
General Info.
Moving charges cause magnetism Magnets have magnetic fields around them.
(Magnetism acts at a distance. ) Magnets always have two, opposite poles
(“north” and “south”). Like poles repel and unlike poles attract. Compasses are magnets Spinning electrons are magnets
Can any material be magnetized?
Non-magnetic material
Magnetic material
No…only materials which have aligned unpaired, electrons can be magnetized!
Ferromagnets (“Permanent Magnets)
Fe, Ni, and Co have unpaired electrons are aligned in areas called “domains”.
Each domain has a magnetic field. When domains are aligned, material has an
overall magnetic field. Pieces of Fe, Ni, and Co become magnetized
when they are placed in a strong magnetic field which aligns their domains .
Electromagnets
DEF: magnet with a field produced by electric current
Usually a coil of wire with current and Fe core
How could you make an electromagnet stronger?
Add coils Increase current Increase amount of Fe inside
This electromagnet uses 210 lb of Fe for the core!
Force Fields
Every ________ is surrounded by a gravitational field because it attracts every other _________.
Every ________ is surrounded by an electric field because it attracts or repels every other ________.
Every _______ is surrounded by a magnetic field because it attracts/repels every other ____________.
Test Your Knowledge
Particle Grav Field? Elec Field? Mag Field?
Stationary neutron
Moving neutron
Stationary proton
Moving proton
Stationary electron
Moving electron
Magnetic Fields
DEF: the area around a magnet where a force acts on a moving charge (another magnet, a current-carrying wire, an electron, etc…)
Represented by field lines which show direction and strength of force; lines point from north to south; closer lines mean stronger field
Bar Magnet
Earth’s magnetic field looks like that of a bar magnet!
South Magnetic Pole
North Magnetic Pole
Earth’s Field
Thought to be caused by moving charges in Earth’s outer core (which is liquid).
Protects life on Earth from harmful radiation (moving charges from space).
Changes strength and direction over time. Sometimes disappears altogether!
What did you learn today?
1. List two types of metals that can be magnetized.
2. Sketch the magnetic field lines for a bar magnet.
3. Sketch the magnetic field lines of Earth.
4. In what ways is Earth’s magnetic field important to life as we know it?
Right hand rule #1
Field around a current-carrying wire—thumb in direction of current, fingers curl in direction of field
Right hand rule #2
Field inside a coil of wire—fingers in direction of current, thumb points in direction of field
Right hand rule 3
Force on a current-carrying wire/moving charge in a magnetic field—Make an “L”…fingers in direction of magnetic field, thumb in direction of current, palm points in direction of force on charge
How would the direction of the force differ on a positive charge? A negative charge?
Right Hand Rules
1. Field around a current-carrying wire—thumb in direction of current, fingers curl in direction of field
2. Field inside a coil of wire—fingers in direction of current, thumb points in direction of field
3. Force on a moving charge in a magnetic field—Make an “L”…fingers in direction of magnetic field, thumb in direction of moving charge, palm points in direction of force on charge