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NOTE: This presentation was not made for public use. Please do not use this presentation without my permission and the permission of each of the authors of the photographs, quotes, and other materials that they contain. Thank you, Vicki Hughes Labs and Activities for this Presentation: Balloon Hair Christmas Lights and Batteries ELECTRICITY AND MAGNETISM Electric charge is a physical property of particles causing them to attract or repel each other WITHOUT TOUCHING! Step 1: Scuff your feet as you walk across carpet. Step 2: Touch a metal doorknob. Step 3: Say OUCH! because you just got a shock! You were shocked by the doorknob because of moving electric charges. Atoms are neutral when they have the same number of electrons and protons. - + Atoms become positively charged when they have fewer electrons than protons. They are then called CATIONS. - + Atoms become negatively charged when they have more electrons than protons. They are then called ANIONS. - + - All electric charge is based on the protons (+ charge) and electrons (- charge) in atoms. Opposites attract! + + Like charges repel. + - - - Like charges repel. Electric Force is the attraction or repulsion between charged particles. An ELECTRIC FIELD is a space around a charged particle where the particle exerts a force. + - OPPOSITE fields attract each other. - + - LIKE fields repel each other. + + + The buildup of charges is known as static electricity. Friction and Electric Charge A balloon rubbed against your hair will cause it to transfer electrons from your hair to the stronger balloon. The hair becomes + and the balloon becomes - . The hair is attracted to the balloon. Balloon Hair Static discharge occurs when built up static charge is suddenly released. Electric Current Electric Current is a continuous flow of electric charges. Water can flow. People can flow. Electrons can flow. Energy Stick Demo Current is measured as the amount of charge that flows past a given point in a certain amount of time. Electric current can flow in one direction…Direct Current: or it can keep changing directions…Alternating Current: Potential Difference (Voltage) = difference between starting point and ending point of a current. high low Resistance is the opposition to the flow of electric currents. Resistance is caused by electrons bumping into particles in matter. Resistance is futile? Nah, but it slows you down! Georg Ohm George Ohm Conductors have LOW resistance and allow current to flow. Let the current flow! George Ohm Insulators have HIGH resistance and DO NOT allow current to flow. Stop that current flow! Conductors and Insulators Electric Fence 0:53 http://www.youtube.com/watch?v=4SIT0aU_FRw George Ohm Insulated wire is made of conductive metal wire surrounded by a nonconductive plastic or rubber coating. George Ohm Semiconductor = partially conducts • circuits can be carved into the surface • circuits are good conductors • very energy-efficient Superconductor = very high conductivity when cold • more efficient than regular conductors Any Questions? NYC Blackout 10:14 http://www.youtube.com/watch?v=6nt0njgVmv4 MAGNETISM Aurora Borealis is a result of the response of Earth’s magnetic field to solar flares. Properties of MAGNETS Magnet = object that attracts certain materials such as iron. Quick Lab: Wooly Willy Properties of MAGNETS Magnetic Poles • A magnetic pole is a region where the magnet is strongest. • All magnets have two magnetic poles. • The poles are called “north” and “south” because they line up with the Earth’s axis. Properties of MAGNETS Magnetic Poles • If you cut a magnet apart in the middle, it will establish two new poles. • Pieces of magnets will always have a north and south pole. N S Poles are on faces. N N N S S MAGNETIC FORCE Magnetic Force is the force exerted over a distance. Repulsion = pushing Attraction = pulling REPELS! ATTRACTS! N S N Activity: Discovering Magnets S MAGNETIC FIELD A Magnetic field is a space around a magnet that exerts a force. N S N S When two OPPOSITE magnetic fields interact, they bend toward each other and pull. N S N S When two of the same magnetic fields interact, they bend away from each other and push. N S S N MAGNETISM Magnetism is due to the movement of electrons. http://www.wimp.com/magnetswork/ ELECTRICITY AND MAGNETISM Electromagnetism is magnetism produced by an electric current. Hello! I am Dr. Oersted. Please join me. Let me tell you how I discovered the relationship between electric currents and magnetic fields. Denmark 1820 ELECTRICITY AND MAGNETISM It all happened like this… I was trying to show my students that electricity and magnetism are not related. I placed a wire with electric S current flowing through it next to a magnet, and nothing happened. Denmark 1820 N ELECTRICITY AND MAGNETISM After class, a student held the wire near the magnet again, but in a different direction. To my surprise, the pointer of the magnet swung toward the wire so it S was no longer pointing to Earth’s magnetic north pole. With more experiments, I was able to show the lines of magnetic fields. Denmark 1820 N ELECTRICITY AND MAGNETISM I’m so proud of my little pooky-bear! Aw, mom! Denmark 1820 Thank you for visiting. Good night everyone. ELECTRICITY AND MAGNETISM The magnetic field created by an electric current flowing through a wire actually surrounds the wire in circles. This magnetic field is stronger as more current flows through the wire. The direction of the magnetic field depends on the direction the current is flowing. ELECTROMAGNETISM Solenoid = a coil of wire with electric current flowing through it, giving it a magnetic field. ELECTROMAGNETISM The magnetic field around a coiled wire has north and south poles like a bar magnet. ELECTROMAGNETISM The magnetic field around a coiled wire is stronger because each turn of the wire has its own field. Therefore, more coils mean stronger magnetism. 31 coils 16 coils ELECTROMAGNETISM Solenoids are the basis for electromagnets. Electromagnet = solenoid wrapped around a bar of iron. How to make an electromagnet 4:58 http://www.youtube.com/watch?v=emlzh9XXWgQ ELECTROMAGNETISM Electromagnetic induction = generating electricity in a wire by moving a magnet nearby. How to make an electromagnet 4:58 http://www.youtube.com/watch?v=emlzh9XXWgQ ELECTROMAGNETISM Project Assignment: (Works = 100; Doesn’t work = 90) Projects count as test grades! Make your own electromagnet using a nail, some wire, and a battery. We will test your battery in class. http://www.youtube.com/watch?v=nMmldOU6t8I ELECTROMAGNETISM Using electromagnets http://www.youtube.com/watch?v=JWh2qT9yiTo ELECTRICITY Electric transformers use electromagnetic induction (moving magnetic fields past electric fields) to change the voltage of electric current. ELECTRICITY The number of coils on each side determines if the current is increased or decreased as it flows through the transformer. ACT L17 Any Questions? Power of Electricity (Transformer Explosions) 10:09 http://www.youtube.com/watch?v=yX5TIDLvMyw