1. Unit 19: Electricity and Magnetism

2. The Nature of Magnetism -The attraction of one object to another - In use for 1,000 of years -Magnets have areas of high attraction =poles -Rules of Attraction: Like repels like opposites attract

3. Magnetic Fields Cannot be seen, but detected Magnetic forces are exerted all around object Magnetic field lines show us the magnetic field

4. Inside a magnet: electron spinMagnetism depends on structure of atoms/matterElectrons orbit the nucleusAlignment dictates magnetism NO Magnetism Magnetism Spinning electrons align Point in the same direction Material that is highly magnetic is termed ferromagnetic =Iron, Nickel, and Cobalt Magnetic fields point in random directions No magnetic field created Weak magnetism, no attraction

5. Magnetic Earth –the northern lights. The interaction of our magnetic field and the Sun’s energy

6. Electricity is related to magnetism • Magnetic fields can produce electrical current in conductors. • Electricity can produce a magnetic field and cause iron and steel objects to act like magnets. • When electricity generates magnetism we term the object an electromagnet. ***Temporary -lose magnetism when current is removed.

7. Where are electromagnets used…? Electric Motors Generators Converts mechanical energy into electrical energy. Most of the energy we use comes from generators!!! -Think fossil fuels to electricity • Convert electrical energy into mechanical energy to do work. • Think household appliances –machines that have to be plugged in.

8. Types of Electrical Current AC = Alternating Current DC = Direct Current Current that flows in one direction Batteries demonstrate DC Charges that move back and forth Electricity in your house

9. Electrical Current • Several factors affect how electricity can flow • Resistance is a property of matter that affects the flow of electricity. Some substances have more resistance than others.

10. Conducting Electricity • As we’ve learned, a conductor is a material that transfers an electric current well. • An insulator is a material that does not transfer current. • A semiconductors is in-between a conductor and insulator.

11. Semiconductors and Current Technologies • The diode is a semiconductor device that acts like a one way valve to control the flow of electricity in electrical circuits. • Solar cells are made of semiconductor diodes that produce direct current (DC) when visible light, infrared light (IR), or ultraviolet (UV) energy strikes them. • Light emitting diodes (LED) emit visible light or infrared radiation when current passes through them. • An example is the transmitter in an infrared TV remote or the lighting course behind the screen in an LED TV or notebook computer screen.

12. Semiconductors we use…

13. Transistors • Transistors are semiconductor devices made from silicon, and other semiconductors. They are used to amplify electrical signals (in stereos, radios, etc.) or to act like a light switch turning the flow of electricity on and off. • Now a days, we can find many transistors in microchips (nanotechnology)

14. Circuits: Current, Resistance, and Conductivity Charge flows through a wire, or material, they create a current. Current produces a magnetic field Measured in ampre (amp or A) A circuit is the flow of current: A) Series B) Parallel

15. Series Circuit One path for current to flow Simple to use, build Breaks in the circuit eliminate flow -one bulb, all out Becomes dimmer when resistors share one current Resistance increases, current decreases Example: Christmas lights

16. Parallel circuits Several paths for current to flow Switches control flow Adding branches, current stays the same Example: the electrical set-up in your house

17. Static Electricity • Friction can cause electrons to be transferred from one object to another. • These charges can build up on an object and be discharged slowly or rapidly.

18. Electrical Safety Short Circuits Grounding Lightning Rods Fuses and Circuit Breakers