21-1: Magnets and magnetic fields
• Like magnetic poles repel; unlike poles attract.
• The direction of any magnetic field is defined as the direction the
north pole would point if placed in the field.
• The magnetic north pole of Earth corresponds to the geographic South
Pole.
21-2: Electromagnetism and magnetic domains
• A magnetic field exists around any current-carrying wire.
• The direction of the current in the wire is a circular path around
the wire.
• The magnetic field created by a solenoid or coil is similar to the
magnetic field of a permanent magnet.
• A domain is a group of atoms whose magnetic fields are aligned.
21-3: Magnetic force
• The direction of the force on a positive charge moving through a
magnetic field can be found using the right-hand rule.
• The magnitude of a magnetic field (B) equals the magnetic force divided
by the charge.
• Magnetic force equals the product of the magnetic field, the current,
and the length of the wire.
• Two parallel current-carrying wires exert opposite (but equal magnitude)
forces on each other. If the currents are in the same direction,
the wires attract each other. If the currents are in the opposite
direction, they repel each other. |
