Magnetic Forces Notes

Electromagnetic Forces - Lesson 1: Magnetic Forces

Identify magnetic forces and explain the strongest force of a magnet.
Model the force of a magnet by demonstrating the basic properties of magnetism and its effects on other objects.
Identify magnetic potential energy and explain its transferring.
Observe where magnetic force is strongest and recognize what materials will interact with a magnet.
Relate magnetic field in compasses.
Explain how magnetic potential energy is affected by the distance and orientation of magnetic poles and how Earth's magnetic field affects compass behavior.
Explain the concept of magnetic domains and how they contribute to the magnetic properties of materials.

Magnet: An object that attracts iron or other materials that have magnetic qualities similar to iron.
Magnetic Materials: Materials that are strongly attracted to a magnet and often contain ferromagnetic elements.
Ferromagnetic Elements: Elements including iron, nickel, and cobalt, which have an especially strong attraction to magnets.
Magnetic Force: A noncontact force of attraction or repulsion created by a magnet.
Magnetic Pole: A place on a magnet where the force it applies is strongest.
Magnetic Domain: Microscopic regions within a magnetic material where the magnetic fields of atoms are aligned in the same direction.
Magnetic Field: The region around a magnet where magnetic forces act.
Magnetic Potential Energy: Stored energy that is the result of interactions of magnetic poles in a magnetic field.

Magnets attract iron or other materials with similar magnetic qualities.
Magnetic materials are strongly attracted to magnets and often contain ferromagnetic elements like iron, nickel, and cobalt.
A magnetic force is a noncontact force of attraction or repulsion created by a magnet.
The magnetic force is strongest at the magnetic poles.

Magnetic field lines can be drawn around a bar magnet to model the force of the magnet.
A magnetic field is the region around a magnet where magnetic forces act.
Compasses are used to relate to magnetic field.

Magnetic potential energy is stored energy resulting from interactions of magnetic poles in a magnetic field.
The difference in potential energy depends on the strength of the magnetic fields, the orientation of the poles, and the distance between them.
Energy must be added to a magnetic field to separate two opposite poles, increasing the magnetic potential energy.
There are two ways to increase magnetic potential energy between two magnets, both requiring a force:
- Increase the potential between two magnets when similar poles are pushed together.
- Increase the potential energy when two opposite poles are pulled apart.

Magnetic materials become magnets when the magnetic fields of the magnetic domains line up in the same direction.
The magnetic fields of the domains combine to form a single magnetic field around the whole object.
Temporary magnets: Materials that become magnets only when close to another magnet. When removed, the domains return to a random arrangement, and the material is no longer magnetic.
Permanent magnets: Materials where the magnetic domains remain lined up, even after being removed from another magnetic field.
Some magnetic materials can be made into permanent magnets by placing them in a very strong magnetic field, causing the domains to align and stay aligned.

A bar magnet is held horizontally, and paper clips are attached to one end to form a chain.
The number of paper clips the magnet can hold is recorded when no more clips stick to the end of the chain.
The procedure is repeated at different locations on the magnet: about 2 cm from the end, near the center, and at the opposite end.
The attraction is compared at the center versus the ends of the magnet.
The ends of the magnet are equally strong, while the middle is weaker.

System X illustrates attractive forces because the magnetic field lines connect to each other.
System Y would need an external force to move the magnets closer together because the magnets are repelling.
In System Y, you could increase the magnetic potential energy by pushing the two magnets closer together because the magnets are repelling.

False: The magnetic domains of a permanent magnet are not arranged randomly.
False: Magnets do not have to touch to affect each other due to the magnetic field.
B: When an object made of magnetic material comes in contact with a magnet, its magnetic domains fall into alignment, and it begins to attract other objects made of magnetic material.
C: To make an item made of magnetic material become a permanent magnet, you can heat it and then let it cool in a very strong magnetic field.
D: The location of the strongest magnetic field is the magnetic poles.
C: The region around a magnet where the magnetic forces act is the magnetic field.
D: The magnetic field of the magnet was too weak to move the paper clip at the farther distance.
A: A compass needle's magnetic north pole points toward Earth's magnetic south pole.
Magnetic
a. Increase potential energy with like poles: Two like poles repel, so moving the magnets closer together will increase the potential energy in the system. You must do work on the magnets to move them together against the repulsive force that acts between them.
b. Increase potential energy with unlike poles: Two unlike poles attract, so moving the magnets farther apart will increase the potential energy in the system. You must do work on the magnets to move them apart against the attractive force that acts between them.