ELECTRICITY AND MAGNETISM

Objectives: After completing this module, you should be able to: Provide evidence that fields exist between objects exerting forces on each other even thogh the objects are not in contact

Magnetism Since ancient times, certain materials, called magnets, have been known to have the property of attracting tiny pieces of metal. This attractive property is called magnetism. N S Bar Magnet N S

Properties of a Magnet Attract or repel other magnets 2. When allowed to swing freely one end will point magnetic north 3. Attract iron

Inside a magnet -The smallest particle of an element is an atom -Atoms contain positively (protons) and negatively (electrons) charges particles Spinning electrons produce magnetic fields In magnets, the spinning electrons are aligned in domains that are in the same direction

But in a magnet or a metal, we can line up to become magnetic MAGNETISM Invisible force of “push” or “pull” by an object with this property Hi! We’re e- (electrons)!!! We usually speed around the outside of the nucleus In these atoms, each e- is going its own way Wagon does not move; forces are not lined up Wagon moves; forces are lined up But in a magnet or a metal, we can line up to become magnetic Lined up atoms/ electrons=Domain

MAGNETS Domains Have domain (lined up atoms) Have polarity (characteristic of magnetism) North-seeking pole (“normal”) South-seeking pole (“reversed”) Cannot have only 1 pole *** magnetic poles cannot be isolated*** Like poles repel; Opposite poles attract

Destroying Magnets When the magnetic domains are forced out of alignment, magnets will be destroyed. This can happen by heat or even a violent strike to a magnet with a hammer

MAGNETS Materials whose atoms can be aligned Elements that can be magnetic Fe: Iron soft iron loses magnetism easily Co: Cobalt used to harden tools Ni: Nickel used to make jewelry Other magnets: Compass Earth

Magnetic Poles The strength of a magnet is concentrated at the ends, called north and south “poles” of the magnet. S N Iron filings N S E W Compass Bar magnet

Magnetic Attraction-Repulsion Magnetic Forces: Like Poles Repel Unlike Poles Attract

Magnetic Field The area in which magnetic forces act

Magnetic Field Lines We can describe magnetic field lines by imagining a tiny compass placed at nearby points. N S The direction of the magnetic field B at any point is the same as the direction indicated by this compass. Field B is strong where lines are dense and weak where lines are sparse. Where is the field strongest?

MAGNETIC FIELDS An area where the force exists; area where force is felt Magnetic field lines Leaves north pole & enters south pole Lines closer together = stronger field NOTICE Strongest at the poles Field lines start at the NORTH pole and travel towards the SOUTH pole

Earth is a Magnet A compass will point to magnetic north because a compass needle has a magnetized needle that spins freely. https://www.youtube.com/watch?v=MZtTVsIOA9c

ELECTROMAGNET Electromagnetism A magnet with a field produced by an electric current Electromagnetism a moving charge (electricity) produces a magnetic field More coils of wire= more current = stronger magnet Bigger battery/stronger current = stronger magnet What’s going on? An electromagnet is a magnet that can be turned on and off. In this experiment, the battery is a source of electrons. When you connect the wire to the battery, the electrons flow through the wire. If there is not a complete circuit, the electrons will not flow. Electrons behave like little magnets and when they flow through a wire, they create a magnetic field, which turns the nail into a magnet that can pick up paper clips and staples!

Solenoids The magnetic field produced by a current has three distinct characteristics: the field can be turned on/off have its direction reversed have its strength changed. Solenoid: A coil of wire with a current. The two ends act like magnetic poles A solenoid with a ferromagnetic core is an electromagnet

Increasing the Strength of electromagnets 1. increase the current in the solenoid Add more loops of wire to the solenoid Use a stronger ferromagnetic material

Temporary Magnets Some materials like steel or iron can be easily magnetized, but lose their magnetism quickly. A magnet that easily loses its magnetism is called a temporary magnet https://mail.google.com/mail/u/0/#inbox/15add8d8ed165a5e?projector=1

CONDUCTORS A material, usually a metal, through which electrons can flow good conductor electrons able to move freely within the atoms of the material poor conductor or insulator electrons are not free to move about the atoms of the other material

ELECTRIC CIRCUIT A path that allows electrons to flow from negative to positive

ELECTRICITY  MAGNETISM Electric currents cause magnetism How can you tell? Compass needle moves when near electrical current - creating an magnetic field

MAGNETISM  ELECTRICITY Moving magnet can generate electricity How can you tell? Electromagnetic induction moving a magnet in and out of a coiled wire created an electrical current without a battery