Transcript File
Applications 0f Electricity Electricity and Magnetism Positive and Negative Charge Conductors and Insulators Superconductivity The Ampere Potential Difference Electric Power Magnets Magnetic Field Electromagnets Electromagnetic Induction Transformers Positive and Negative Charge Opposites attract-Same charges repel Positive and Negative Charge Electrons are stripped from one component and transferred to the other to cause both to be oppositely charged. Semiconductors Transistors are switches that conduct electricity only when a second source of electricity is energized. A John Bardeen Nobel Prizes in 1956 and 1972 for developing the transistor and superconductivity. B C A current will not flow from A to B unless C is energized. Superconductivity Superconductivity refers to the loss of all electrical resistance by certain materials at very low temperatures. Substances that are superconducting at 150K are now known which is warmer than liquid nitrogen (77K). The Ampere The Ampere is a measure of how much electrical current is flowing and is measured in units of amps. The Ampere The current varies depending on the force behind the current and the resistance to flow. Electric Power The power of an electric current is the rate at which it does work and is equal to the product of the current and the voltage of a circuit: The unit of electric power is the watt.The commercial unit of electric energy is the kilowatthour (kWh). Electric Power Typical Power Ratings Appliance Stove Clothes Dryer Heater Dishwasher Photocopier Iron Vacuum Cleaner Coffee Maker Refrigerator Portable Sander Fan Personal Computer TV Receiver Fax Transmitter/Receiver Charger for Electric Toothbrush Power (W) 12,000 5,000 2,000 1,600 1,400 1,000 750 700 400 200 150 150 120 65 1 Magnets A magnet is an object or a device that gives off an external magnetic field. Every magnet has a north pole and a south pole. Magnet Field Magnetic fields are areas where an object exhibits a magnetic influence. The fields affect neighboring objects along things called magnetic force lines. Magnetic poles are the points where the magnetic field lines begin and end. Magnetic force lines. Electromagnets An electromagnet consists of an iron core placed inside a wire coil. The magnetic field strength of a wire coil carrying an electric current increases in direct proportion to the number of turns of the coil. Electromagnets An electromagnet can be used to move large quantities of metal. When the current is on the magnet will pick up the metal. When you want to drop it you turn off the power and the electromagnet is disabled and the metal drops. Electric Motors An electric motor uses the sideways push of a magnetic field to turn a current-carrying wire loop. Electric motors use a commutator to change the direction of the current in the loop. Alternating current electric motors do not use commutators. Electromagnetic Induction The effect of producing an induced current is known as electromagnetic induction. The direction of the induced current can be reversed by reversing the motion of the wire or reversing the field direction. The strength of the current depends on the strength of the magnetic field and the speed of the wire's motion. Michael Faraday (17911867) built the first electric motor and discovered magnetic induction. The stationary windings of a large electric motor. magnetic forces underlie the operation of such motors. Sharks navigate with the help of the earth’s magnetic field. They detect the field using electromagnetic induction. Transformers A transformer is a device composed of two unconnected coils, usually wrapped around a soft iron core, that can increase or decrease the voltage of ac current. A transformer is used to step the voltage down and the power up (P=IV) so that we can use it. Low power is desired for the transport of electricity long distances to avoid loss of energy to heat loss. A moving coil activated by voice vibrations is used as a microphone. The coil induces a current in the magnet that can be amplified or recorded. A taperecorder records signals from a microphone on magnetic tape which then can be run across a magnet and played back. 1. Who won the Nobel Prizes in 1956 and 1972 for developing the transistor and superconductivity.? 2. It refers to the loss of all electrical resistance by certain materials at very low temperatures.? 3. It is a measure of how much electrical current is flowing and is measured in units of amps.? 4. These are areas where an object exhibits a magnetic influence.? 5. It is consists of an iron core placed inside a wire coil and also used to move larges quantities of metal.? 6. What is the effect of producing an induced current.? 7. It is an object or a device that gives off an external magnetic field.? 8. What do you called the points where the magnetic field lines begin and end. ? 9. It is a device composed of two unconnected coils, usually wrapped around a soft iron core, that can increase or decrease the voltage of ac current. ? 10. Use to change the direction of the current wire loop.?