Download Magnetism Section 1 Magnetism A. —the properties and interactions

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.