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Download Magnetism Section 1 Magnetism A. —the properties and interactions
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Magnetism Section 1 Magnetism A. _________________—the properties and interactions of magnets 1. Interaction between two magnets called magnetic _________________ increases as magnets move _______________ together. 2. A magnetic ________________, which exerts the magnetic ______________, surrounds a ___________________, and is strongest closest to the magnet. B. Magnetic _______________—the __________________ of a magnet where the magnetic force exerted by the magnet is strongest 1. All magnets have a ___________ pole and a __________ pole. 2. _____________ poles repel. _______________ poles attract. 3. ___________________ has magnetic poles. a. A ____________________ needle is a small bar magnet that can freely rotate. b. A compass _____________________ always points to Geographic north. C. Magnetic materials—___________________________________ 1. __________ magnetic field created by each atom exerts a force on _____________________ atoms. 2. Magnetic __________________—groups of atoms with __________________ magnetic poles a. In a magnet, the like poles of all the domains _______________ in the same direction. b. Permanent magnets ________ made by placing a magnetic material in a strong magnetic field, forcing ________ large number of magnetic ________________ to line _________. Section 2 Electricity and Magnetism A. Moving _____________________ and magnetic ____________________ 1. Moving ___________________, like those in an electric __________, produce magnetic fields. a. The magnetic field around a __________________-carrying wire forms a circular pattern about the _______________. b. The _________________ of the field depends on the direction of the __________________. c. The strength of the magnetic _____________ depends on the amount of ___________________ flowing in the wire. B. __________________________—a temporary magnet made by placing a piece of iron inside a current carrying ______________ of wire 1. Magnetic field _____ present only when _______________ is flowing in the wire coil. 2. Increase strength of the magnetic field by adding more turns to the wire ____________ or increasing the current passing ____________________ the wire. 3. Magnetic __________________ of electromagnets can be controlled by changing the electric current flowing through _______ wire coil. 4. ______________ electrical energy into mechanical energy to do _____________ C. ____________________________—a device that uses an electromagnet to measure electric current D. Electric _________________—a device that changes electrical energy into mechanical energy 1. Contains an electromagnet that is ____________ to rotate between the poles of a permanent, _________________ magnet. The coil in the electromagnet is connected to a source of _________________ current. 2. When a current _________________ through the electromagnet, a magnetic field is produced in the coil. 3. Changing the direction of the current causes the coil in an electric motor to keep ______________. 4. Rotation ________________ of electric motors can __________ controlled. a. Vary the amount of current flowing ____________________ the coil. b. When more current flows through the coil, the electromagnet’s _____________________ field becomes stronger, the magnetic force between the coil and the permanent magnet increases, and the coil _____________ faster. Section 3 Producing Electric Current A. From ____________________ to electrical energy 1. Electromagnetic _______________________—the production of an electric current by moving a loop of wire through a magnetic ____________ or moving a magnet through a wire loop 2. __________________—a device that produces electric current by rotating a _________ of wire in a magnetic field a. The wire coil is _______________around an iron core and placed between the poles of a permanent magnet. b. Coil is rotated by an outside _________________ of mechanical energy. c. As the coil turns within the magnetic field of the permanent magnet, an electric current flows through the ________________. d. _________________ of the current in the coil in a generator changes twice with each revolution. 3. Generating ____________________ a. Electricity used in the home comes from a _________________ plant with huge generators. b. Coils ________ electromagnets in the generators usually connected to a turbine—a large wheel that rotates when pushed by water, _________, or steam. B. Direct and ______________________ currents 1. Direct current (____) is ____________ that flows in only one _______________ through a wire. 2. Alternating current (____) reverses the direction of the current _________ in a regular way. a. In ____________ America, generators produce alternating current at a frequency of 60 cycles per second, or 60 Hz. b. A 60-Hz alternating current changes direction _________ times each second. C. Transformer—_____ device that increases _______ decreases the _____________ of an alternating current 1. Made of two __________ (primary and secondary) wrapped around _____ same iron core. 2. Changing ______________ in primary coil creates changing magnetic field around the iron core, which induces an alternating current in the ___________________ coil. 3. A step-______ transformer increases voltage. The __________________ coil has more turns of wire than the primary coil does. 4. A step-___________ transformer decreases voltage. The ________________ coil has fewer turns of wire than the primary coil does. 5. Power carried in power lines as high as 750,000 V is __________________ by step-down transformers to household current (AC) of 120 V.