Magnetism
Magnets and Magnetic Fields
Magnets
______– objects, usually metallic, that can attract or repel certain other objects, such as iron
Have two poles: ______and ______(or North-seeking and South-seeking)
Will point toward the Earth’s magnetic poles
North points toward Earth’s Magnetic South Pole and South points Earth’s Magnetic North Pole
Like poles ______and opposite poles ______
No matter how many times you cut a magnet, it will always have both a North and South Pole
Used in multiple applications – electromagnets, motors, recording devices, maglev trains
Earth acts like a giant magnet
Magnetic Domains
Moving ______cause magnetic fields
Every electron or proton is constantly in motion
Always generating a ______
Most charged particles ______each other out
Some substances have the charges moving in such a way that the magnetic fields line up
______– includes iron, cobalt, and nickel
Can be effected by a ______
In ferromagnetic materials, the charges group together in large groups called ______
Most of the time, the domains are oriented randomly – ______
In natural magnets or in substances effected by a magnet, the domains are oriented more closely
Aligned magnetic domains ______the magnetic field
Substances can be made into ______magnets
Prolonged exposure to a permanent magnet can cause ferromagnetic materials to become magnetic
Stroking iron with a magnet
Being near a magnet for a long enough time – ______magnetism
Magnetically ______materials are easy to magnetize, but lose their magnetism easily
Magnetically ______materials do not magnetize easily, but will keep their magnetism longer
To break a magnet, expose it to heat and cold or hammer it
Magnetic Fields
______– a region in which a magnetic force can be detected
Surrounds any magnetized material, including Earth
Earth’s magnetic field ______us from ultraviolet radiation, x-rays, gamma rays, and the solar wind from space and traps the atmosphere close to the surface
Magnetic fields run from the North Pole to the South Pole of a magnet
Can be drawn similar to electric field lines
The more lines, the ______the field
Magnets are stronger at the poles
______– the number of magnetic field lines that cross a certain area at right angles to that area
Symbol is ΦM
Magnetic flux = surface area * magnetic field component normal to the plane of surface
ΦM = A * B * cosθ
A = surface area (meters squared, M2)
B = Magnetic Field Strength (Teslas, T)
θ = angle between perpendicular and the magnetic field , usually going to be 0.0° at our level
Earth’s magnetic field is currently oriented so that magnetic south is in the geographic ______and magnetic south is located in geographic ______
The magnetic field ______itself periodically
Can be observed at sea-floor spreading areas
______– the difference between true north (as defined by the Earth’s axis of rotation) and the North Pole of a compass
Varies everywhere on Earth
Essentially zero in the center of North America
20° East of true North in the State of Washington
Source of Earth’s magnetic field is believed to be ______in the molten core of the Earth
As the molten metal moves, it ______a magnetic field
Stronger planetary magnetic fields may cause a faster planetary rotation