Magnetism: Magnetic force and Poles

• A magnet attracts iron or materials with similar magnetic qualities.
• Materials strongly attracted to a magnet are magnetic materials.
• Magnetic force is the attraction or repulsion created by a magnet.
• Magnetic force is a noncontact force.

Magnetic Poles

• A magnetic pole is where the force of a magnet is strongest.
• All magnets have a north and south pole.
• Breaking a magnet results in each piece having both a north and a south pole.
• Magnets repel like poles and attract opposite poles, even without touching.
• A magnetic field surrounds all magnets.
• Magnetic fields apply forces to other magnets and materials, even at a distance.
• Magnetic force increases as magnets move together and weakens as they move apart.
• Iron filings around a magnet display the magnetic field pattern.
• Magnetic field lines are closest at the poles, indicating the strongest force.
• Stronger magnets exhibit stronger magnetic fields.
• Magnetic objects experience stronger forces in stronger magnetic fields.

Electric Charges

• There are two types of electric charge: positive and negative.
• Oppositely charged particles attract, while similarly charged particles repel.
• An electric field surrounds a charged object applying force to other charged objects, even without contact.
• Electric force is a noncontact force.
• An object's electric field either attracts or repels other charged objects.
• The strength of electric force depends on the amount of charge and the distance between objects.
• Rubbing hair causes charged particles to move, creating a static charge.
• More brushing increases the charge transfer and force of attraction.
• Electric fields surround these charges which are more intense closer to the charges.
• The shorter the distance, the stronger the electric force.

Electrically Charged

• Friction between neutral objects can cause a transfer of charged particles, giving each object a charge.
• An object is electrically charged when it has an unbalanced amount of positive or negative charge.
• An object with equal amounts of positive and negative charge is electrically neutral.
• Neutral objects can be attracted to charged objects.
• Charged particles can transfer between objects.

Electric Insulators

• Electric insulators are materials like glass, rubber, wood, and air where charges cannot easily move.
• Electric conductors are materials like copper and aluminum where charged particles can easily move.
• When conducting objects with unequal charges touch, charge flows from the object with more negative charge to the object with less.

Electromagnets

• Electric current is a stream of charged particles, which is surround by a magnetic field.
• Moving charged particles create a magnetic field.
• The magnetic field around a current-carrying wire forms closed circles perpendicular to the current.
• When current stops, the magnetic field disappears.
• The magnetic field is strongest near the wire.
• Electromagnets are made by wrapping a wire around a ferromagnetic material like iron.
• The ferromagnetic core increases the coil's magnetic field strength.
• Increasing the loops in the coil increases the magnetic field of the electromagnet.

Magnetic Domains

• Atoms in a material form groups called magnetic domains.
• A Magnetic domain is a region where the magnetic fields of atoms align.
• Nonmagnetic materials have no domains, or random alignment, canceling each other.
• Magnetic materials have organized domains, not aligned throughout the material, allowing interaction with magnets but no independent field.