Understanding Magnetism: Permanent, Ferro, Para, and Diamagnetic Materials
Understanding Magnetism
Permanent Magnet: Once magnetized, remains magnetized.
Ferromagnet: Easily magnetized (iron, nickel, cobalt, some rare-earth metals, magnetite).
Paramagnet: Magnetized with more difficulty.
Diamagnet: Repels magnetic fields (slightly) – “not magnetic”.
Materials are broken into smaller chunks called “domains”. Each domain has a miniature magnetic field.
Domain Differences
Even if materials look the same, at a smaller level their domains could be different – hence why some are magnets (or magnetize easily) and some don’t.
Factors Affecting Magnet Strength
Material, temperature, condition, size and shape, distance. At the poles, a magnet is at its strongest (either repelling or attracting). The force of magnets can be felt over a distance.
Visualizing Magnetic Force
To help visualize the force, draw field lines. Always draw arrows from N to S, and closer lines indicate a stronger force. True North ≠ Magnetic North (the difference is “declination”).
Magnetic Attraction and Energy
Opposite poles naturally attract. Close together = low-energy state. It takes an outside force to pull the magnets apart. Applying force = increasing energy. Protons don’t move from one atom to another (too large). Instead, electrons do when energy is added to the system (typically through friction). Objects can be charged by conduction, induction, or friction.
Electroscope
Electroscope: a device used to qualitatively demonstrate the effect of charged objects.
Field Lines
FIELD LINES: INTO – charges and OUT OF + charges. Shaped like spokes on a wheel. More field lines = stronger charge.
Energy and Fields
Energy can be increased in a system when you do work on objects.
GPE=mgh
EPE= qV
Electric Field = Magnetic Field (perpendicular). A magnet needs to be moving to cause a current in a wire. Increase current by using a big magnet or moving the magnet quickly. This can also cause small changes in the electrons in other materials (non-wires).
Generators and Motors
- Generator: Mechanical Motion → Electricity.
- Motor: Electricity → Mechanical Motion.
Key Concepts
- Permanent magnets can’t be made from using only copper.
- Dropping a magnet on the floor can make it weaker.
- Magnetic fields form loops from N-S.
- Both magnetic and electric force have an inverse relationship with distance between objects.
- Induction does NOT have electrons move from object to object.
- An electric field can be created by stationary and moving charged particles.
- A magnetic field can be created by moving charged particles.
- Electromagnetic induction: current generated in a coil from a changing magnetic field that was generated by an alternating current.
Railgun
Railgun: one rail + charged and one – charged. Rubbing a magnet on a wire faster or using a bigger magnet could increase the amount of electricity (current) generated in a coil from a magnet.
Electromagnetism
Electromagnetism: the interaction of electric currents or fields and magnetic fields. A permanent magnet’s strength depends upon the material used in its creation. The strength of an electromagnet can be adjusted by the amount of electric current allowed to flow into it. As a result, the same electromagnet can be adjusted for different strength levels.
Tesla Coil
A Tesla coil consists of two parts: a primary coil and a secondary coil, each with its own capacitor. (Capacitors store electrical energy just like batteries.) The two coils and capacitors are connected by a spark gap — a gap of air between two electrodes that generates the spark of electricity. An outside source hooked up to a transformer powers the whole system. Essentially, the Tesla coil is two open electric circuits connected to a spark gap.